Appl. Brochure Nr. 42 Metals in the Mining Industry

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42Application Brochure

General Titrators

Selected Applications Titration of Metals in the Mining Industry

Met

als

Min

ing

EDITORIAL Dear Reader Thank you for reading these lines and looking in our Application Brochure. You can expect detailed descriptions of selected metal determinations via titrimetric analysis. We don't present you a glossy brochure. It is a cookbook with proven recipes.Yet the result is not a cake but a reliable, precise and accurate number. Please follow the recipes diligently to get the most out of your analysis efforts. Titrators of METTLER TOLEDO support you. Easy to use thanks to One Click™ operation and color touchscreen. Simple to set instruments parameters thanks to preprogrammed methods. Smooth to link with your lab data system thanks to LabX software. “The proof of the pudding lies in the eating”, goes a British saying. Thus, we wish you successful "cooking and eating" with our recipes. We are sure that you achieve the top quality results you are working for.

Hans-Joachim Muhr Georg Reutemann Market Support Manager Manager New Projects and BA Titration Business Development LAB Division

METTLER TOLEDO

Contents

Method Title Gold - Au

M180 Estimation of the Approximate Gold Content in Alloys

M207 Titration of Gold -Au(I)- in a Standard Cyanide Solution

M297 Standardization of Cerium Sulfate vs. Hydroquinone

M298 Standardization of Hydroquinone and Cerium Sulfate with Pure Gold

M299 Determination of Gold

Silver - Ag

M195 Determination of Silver in Silver Alloys

Cyanide – CN-

M196 Determination of Free Cyanide in a Cyanidic Silver Bath

M465 Determination of Free Cyanide and Silver

Palladium – Pd

M462 Determination of Palladium Content

Copper – Cu

M460 Copper Content in Copper Mining Solutions

Iron – Fe

M459 Automated Determinaton of Iron Content in Iron Ores

M622 Determination of Total Iron Content of Iron Ores

M060 Determination of Iron (Fe(II) ) and Sulphuric Acid (H2SO4)

Chromium – Cr

M463 Determination of Cr(III) by Back-Titration in an Electroplating Bath

M464 Iodometric Titration of Cr(VI) in an Electroplating bath

Manganese – Mn

M461 Determination of Manganese in Manganese Ores

METTLER TOLEDO - I - Metals and metal mining

METTLER TOLEDO

Method Title Aluminum - Al

M466 Aluminum Content in Aluminum Ore (Bauxite) – Bayer Liquor

Boron - B

M222 Determination of Boric Acid in Acidic HCl/HF Solutions

Titanium -Ti

M467 Titanium Content in Mining Solutions

Cobalt - Co

M458 Determination of Cobalt Content in Alloy

Uranium - U

M292 Determination of Uranium according to Modified Davies-Gray Method

METTLER TOLEDO - II - Metals and metal mining

METTLER TOLEDO

METTLER TOLEDO - III - Metals and metal mining

Introduction

Metals with all their different material properties have contributed fundamentally to the progress of mankind. Since metals have been available centuries and millenniums ago, a continuous flow of innovations and new developments emerged. Weaponry and ornaments were first produced from metals such as copper, bronze or iron and ended the Neolithic stone age some 5000 years ago.

Metals are gained after a long and energy consuming production process from ores. At the end, there is the pure metal which consecutively undergoes further modifications according to its final use. The complete mining process from metallic ores to pure metal can be described as follows:

From the chemical point of view, the reduction reaction of the metal cations of the ores to the elemental metal is in the center of the mining process. Before this step, suitable preparation of the ores such as concentration or extraction is required to separate the metal compound from the rocks.

At the beginning, the geologic survey localizes the mineral deposits and assays of the ores evaluate yield expectations and extraction costs. At the end, melting in a blast or electric arc furnace in the presence of a suitable reducing agent such as carbon turns the metal cations from the minerals into the elemental metal. Subsequent refining by electrolytic techniques or other processes produces the pure final metals.

The determination of the metal content is thus required at different stages but is always related to the economics of the metals mining process. During the survey, the metal content is a decision factor if the ore is worth mining. Later purposes of analysis are process efficiency and safety or quality and purity of the final products.

Noble metals such as gold or silver being nearly resistant to corrosion occur thus as the metal already. The important production process besides the mining is the extraction of the noble metal from its gangue, a process which also requires careful monitoring and control.

Titration (titrimetric analysis) is a quantitative analytical method which accompanies the entire chain of the metal mining. It is a well proven and widespread analysis which nowadays comes with a large extent of automation from sample preparation to addition of reagents, result calculation and data storage.

METTLER TOLEDO's Excellence line titrators offer the right solution of titrator units, accessories such as sample changers or burettes and software to successfully compete with almost any requirements of titrimetric analysis. The easy One Click™ operation, robust and qualified instruments as well as moderate costs of purchase allow the use of titrators at all mining sites and in small testing labs equally.

Geologic survey

Assay of ores

Digging, mining

Size reduction

Concen-tration

Extrac-tion

Refining FinishingRetion duc-

METTLER TOLEDO

The main advantages of titrimetric methods such as linearity and high precision unfurl well appreciated benefits for the user:

• Linearity: Unlike spectroscopic techniques, titration is linear over the whole measuring range. Even at high concentrations, no dilution is required.

• High precision: Typical precision of titrimetric analyses is around 0.5%. In case of pure silver, the relative standard deviation can be as precise as 0.05%.

Equally important are the many titration methods available for the different metals which are tested and approved by a long history of practice.

The metals can be divided into different groups either depending on their properties, their occurrence, their use or other criteria. Commonly, base metals, iron and noble metals are distinguished.

Base Metals Examples: • Copper • Aluminium • Nickel • Zinc • Lead • Magnesium • Cobalt

Metals

Noble Metals Examples: • Gold • Silver • Platinum • Rhodium

Ferrous Metals Example: • Iron

Ores contain the metals usually as oxides, sulfides or silicates. As an example, the oxides magnetite Fe3O4 and hematite Fe2O3 are the major iron bearing minerals. Chalcopyrite CuFeS2, a sulfide, is the main mineral for the production of copper.

Besides the pure metals, alloys and metal compounds play an important role in our current civilization. Structures of skyscrapers and cars are made of metals and alloys to add the requisite strength and mechanical stability. Metals carry the electricity from the point of generation to the point of use hundreds of kilometers (or miles) apart. Or a third example, catalysts from metals or metal compounds support chemical reactions to produce ammonia (from nitrogen and hydrogen) or polymers (from ethylene or propylene), reduce exhaust gases (e.g. in cars) and harden fats and oils (e.g. for use in margarines).

METTLER TOLEDO - IV - Metals and metal mining

METTLER TOLEDO

Literature [1] O. Bazhko,

“Application of redox titration techniques for analysis of hydrometallurgical solutions”, in: “Hydrometallurgy Conference 2009”, The Southern African Institute of Mining and Metallurgy, 2009.

[2] A. I. Samchuk, A. T. Pilipenko, “Analytical Chemistry of Minerals”, Translated from the Russian by S. V. Ponomarenko VNU Science Press, Utrecht, The Netherlands, 1987.

[3] K.-H. Spitz, J. Trudinger, “Mining and the Environment: From Ore to Metal”, CRC Press, Taylor & Francis Group, 2009

[4] H. Hartman, J. Mutmansky, “Introductory Mining Engineering”, John Wiley and Sons, 2nd Edition, 2002.

[5] B. Lottermoser, “Mine Wastes: Characterization, Treatment and Environmental Impacts”, Springer, Berlin Heidelberg New York, 2nd Edition, 2007.

Links: - www.slideshare.net/LondonMiningNetwork/ore-mineralogy-and-orebodies

Excellent introduction on mining enginering.

- www.infomine.com InfoMine is a provider of mining knowledge online, delivering content via website, through corporate intranets, and by email.

- www.greatmining.com Information related to mining and mineral covering all aspects of global mining process from the base exploration to development and from environmental to social issues.

- www.onemine.org Comprehensive collection of data on mining and minerals based research including technical documents, conference papers, articles, pre-prints and late papers.

METTLER TOLEDO - V - Metals and metal mining

http://www.slideshare.net/LondonMiningNetwork/ore-mineralogy-and-orebodies

http://www.infomine.com/

http://www.greatmining.com/

http://www.onemine.org/

METTLER TOLEDO

METTLER TOLEDO - VI - Metals and metal mining

METTLER TOLEDO Application M180-2010

Estimation of the Approximate Gold Content in Alloys Estimation of gold content by reduction of gold ions in solution to elemental gold after addition of hydroquinone. Excess hydroquinone is determined by redox titration with cerium sulfate. This method is a fast test of the gold content. Application M299 allows for an accurate determination.

Preparation and Procedures CAUTION: work in a fume hood since gases are produced during dissolution of gold.

Alloy dissolution:

- Press alloys as thin as possible using a rolling device so that the dissolution is easier.

- Use an ultrasonic bath especially for silver containing alloys, because silver chloride does passivate the gold surface.

- Weigh 20-30 mg gold sample in a glass beaker.

- Add 5 mL HCl 32% and 1.5 mL HNO3 65%, and dissolve it on a heating plate (110-130°C).

- Evaporate to almost dryness, but never evaporate to complete dryness. This causes the reduction of gold leading to false results!

- Add again 5 mL HCl 32%, and evaporate again to almost dryness, but never evaporate to complete dryness.

- Rinse the beaker walls with a small amount (max. 10 mL) of deionized water or 5 mL 32% HCl. Cool down the sample before titration.

Titration:

- Place the titration beaker with the prepared sample on the manual titration stand.

- 30 mL HCl 0.1 mol/l will be pumped in automatically.

- Hydroquinone will be added automatically. The back titration is performed using a DMi140 redox electrode with cerium sulfate 0.01 mol/l.

Remarks

1. Pure gold is used as a standard.

2. Theoretical consumption: - 20 mg gold corresponds to 7.5 mL

hydroquinone, c(1/2 C6H6O2)=0.05 mol/L, and 7.0 mL cerium sulfate, c(Ce(SO4)2)=0.01 mol/L.

- 1 mL hydroquinone c c(1/2 C6H6O2)=0.05 mol/L corresponds to 5 mL cerium sulfate, c(Ce(SO4)2)= 0.01 mol/L.

Literature: METTLER TOLEDO Application Brochure “Gold and Silver”, ME-724613, 04/1994.

Sample Various gold alloys with unknown gold content, 30-60 mg

Compound Gold, Au M(Au) = 196.967 g/mol, z = 3

Chemicals 32% hydrochloric acid, HCl 65% nitric acid, HNO3 0.1 mol/L hydrochloric acid, HCl

Titrant Hydroquinone, C6H6O2 c(1/2 C6H6O2) = 0.05 mol/L Cerium(IV) sulfate, Ce(SO4)2 c(Ce(SO4)2) = 0.01 mol/L

Standard See M297 and M298 for standardization of titrants

Indication DMi140-SC (Pt ring) combined redox electrode

Chemistry Reduction with hydroquinone: 2Au3+ + 3C6H6O2 → 2Au + 6H+ + 3C6H4O2

Titration of excess hydroquinone: C6H6O2 + 2Ce4+ → C6H4O2 + 2Ce3+ + 2H+

Calculation Content (%): R1 = 100*(H[Hydroquinone]-Q[2])*C/m C1 = M/(1000*z) Content (carat): R2= 24*R1*C2 C2 = M/(1000*z) H[Hydroquinone] (Tx) or H5(DL7x) = dispensed hydroquinone amount

Waste disposal

HCl/HNO3: Neutralization with NaOH Hydroquinone: Evaporate solution,special waste Cerium: Precipitate with NaOH, filtrate, special waste Gold: Filtrate solution, special waste

Author, Version

MSG Anachem, April 1993 Revised January 2010/C. De Caro

METTLER TOLEDO Page 1 of 5 Titration Application M180-2010

Instruments - T50/T70/T90 Titration excellence, DL70ES/DL77 Titrators - XS205 Balance

Other titrators: This method can be also run with the DL55 and DL58 titrators (without peristaltic pump).

Accessories - 2 x 10 mL DV1010 burettes - Additional dosing unit (Tx) ME-51109030, or burette drive (DL5x, DL7x) - Glass titration beaker ME-101446 - SP250 Peristaltic pump ME-5108016

Results

Not available

Titration curve

1st Titration: 2Au3+ + 3C6H6O2 → 2Au + 6H+ + 3C6H4O2

2nd Titration: C6H6O2 + 2Ce4+ → C6H4O2 + 2Ce3+ + 2H+



Table of measured values

Not available

Comments

Principle:

To determine pure gold or its content in alloys the precipitation method with hydroquinone has been selected. Most of the associated metals do not interfere with the determination. As the precipitation of gold is too slow to execute a direct titration with hydroquinone, an excess of hydroquinone is added to the dissolved gold. The excess is titrated back with cerium(IV) sulfate:

1. Oxidation of gold: Gold is oxidized to Au3+ by aqua regia (conc. HCl/conc. HNO3 3:1 v/v). 2. Precipitation of gold:

Au3+ is reduced by excess hydroquinone and precipitates, and quinone is formed. Au3+ + 3 C6H6O2 = 2 Au + 3 C6H4O2 + 6 H+

3. Excess hydroquinone is oxidized by cerium(IV) sulfate (back-titration): 2 Ce4+ + C6H6O2 = C6H4O2 + 2 Ce3+ + 2 H+

Estimation of gold content (within approx. 3%):

With this method the gold content can be determined within approximately 3%. The gold content can then be determined accurately with application M299.

This test method consists of two titration functions:

1st TITRATION function: The gold reduction with hydroquinone is performed by a titration in order

• to determine the total amount of C6H6O2 dispensed • to obtain an excess of at least 1 mL C6H6O2 (titrant addition dV = 0.5 mL).

The total amount of hydroquinone dispensed is stored as auxiliary value H5.

2nd TITRATION function: Excess hydroquinone is back-titrated back with cerium(IV) sulfate.

Maintenance of the electrode:

We recommend to always clean the electrode after 6 gold titrations because gold contaminates the platinum ring by forming a thin layer: Place it for two minutes in aqua regia and rinse thoroughly with deionized water (See also leaflet of the DMi140-SC electrode).

Literature:

- A. Chow, “The Stability of Gold Solutions”, Talanta 18 (1971), pp. 453-456.

- S.C. Soundar Rajan and N. Appala Raju, “Titrimetric Determination of Gold by Precipitation with Hydroquinone”, Talanta 22 (1975), pp. 185-189.


DL70ES/DL77 Titrator

Method test Approximate gold content

Version 10-April-1993 11:09

Title

Method ID .......................... test

Title .............................. Approximate gold content

Date/time .......................... 10-April-1997 11:09

Sample

Number samples ..................... 1

Titration stand .................... Stand 1

Entry type ......................... Weight m

Lower limit [g] ................ 0.03

Upper limit [g] ................ 0.06

ID1 ................................ Gold

Molar mass M ....................... 196.967

Equivalent number z ................ 3

Temperature sensor ................. Manual

Pump

Auxiliary reagent ................. HCl 0.1 mol/L

Volume [mL] ........................ 40.0

Stir

Speed [%] .......................... 50

Time [s] ........................... 10

Titration

Titrant ............................ 1/2 C6H6O2

Concentration [mol/L] .............. 0.05

Sensor ............................. DM140-SC

Unit of meas. ...................... mV

Titration mode ..................... EQP

Titrant addition ............... INC

dV [mL]...................... 0.5

Measure mode ................... EQU

dE [mV]...................... 0.5

dt [s]....................... 2.0

t(min) [s]................... 10.0

t(max) [s]................... 40.0

Threshold ...................... 200.0

EQP range ...................... Yes

Limit A...................... 800

Limit B...................... 500

Maximum volume [mL] ............ 20.0

Termination after n EQPs ....... Yes

n = ......................... 1

Evaluation procedure ........... Standard

Auxiliary value

ID text ........................... Amount of C6H6O2

Formula ............................ H5=Q+QEX

Stir

Speed [%] .......................... 50

Time [s] ........................... 120

Titration

Titrant ............................ Ce(SO4)2


Sensor ............................. DM140-SC

Unit of meas. ...................... mV


Titrant addition ............... DYN

dE(set) [mV]................. 8.0

Limits dV.................... Absolute

dV(min) [mL]............ 0.02

dV(max) [mL]............ 0.2

Measure mode ................... EQU

dE [mV]...................... 0.5

dt [s]....................... 2.0

t(min) [s]................... 3.0

t(max) [s]................... 30.0

Threshold ...................... 400.0

EQP range ...................... Yes

Limit A...................... 500

Limit B...................... 700



n = ......................... 1


Calculation

Result name ........................ content

Formula ........................... R=100*(H5-Q[2])*C/m

Constant ........................... C=M/(1000*z)

Result unit ........................ %

Decimal places ..................... 1

Calculation

Result name ........................ content

Formula ........................... R2=24*(H5-Q[2])*C2/m

Constant ........................... C2=M/(1000*z)

Result unit ........................ carat

Decimal places ..................... 1

Report

Output unit ....................... Printer

All results ........................ Yes

Titration Excellence

Title

Type General titration

Compatible with T50 / T70 / T90

ID m180

Title Approximate gold content

Author admin

Date/Time 01.03.2010 10:30:00

Modified at 01.03.2010 10:30:05

Modified by admin

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Gold

Entry type Weight

Lower limit 0.03 g

Upper limit 0.06 g

Density 1.0 g/mL

Correction factor 1.0

Temperature 25.0°C

Entry Arbitrary

003 Titration stand (Manual stand)

Type Manual stand

Titration stand Manual stand 1

004 Pump

Auxiliary reagent HCl 0.1 mol/L

Volume [mL] 40.0

005 Stir

Speed 50%

Duration 10 s

Condition No

006 Titration (EQP) [1]

Titrant

Titrant 1/2 C6H6O2

Concentration 0.05 mol/L

Sensor

Type mV

Sensor DMi140-SC

Unit mV

Temperature acquisition

Temperature acquisition No

Stir

Speed 40%

Predispense

Mode None

Waiting time 0 s

Control

Control User

Titrant addition Incremental

dV 0.5 mL

Meas. val. acquisition Equilibrium controlled

dE 0.5 mV

dt 2 s

t (min) 10 s

t (max) 40 s

Evaluation and recognition

Procedure Standard

Threshold 200 mV/mL

Tendency Negative

Ranges No

Add. EQP criteria No

Termination

At Vmax 20.0 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQP 1

Combined termination

criteria No

007 Auxiliary value

Name Hydroquinone

Formula H= Q[1]+QEX[1]

Limits No

008 Stir

Speed 50%

Duration 120 s

Condition No


Titrant

Titrant Ce(SO4)2


Sensor

Type mV

Sensor DMi140-SC

Unit mV




Stir

Speed 40%

Predispense

Mode None

Waiting time 0 s

Control

Control User

Titrant addition Dynamic

dE(set value) 8.0 mV

dV(min) 0.02 mL

dV(max) 0.2 mL


dE 0.5 mV

dt 2 s

t (min) 3 s

t (max) 30 s


Procedure Standard

Threshold 400 mV/mL

Tendency Positive

Ranges No


Termination

At Vmax 10.0 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQP 1


criteria No

010 Calculation R1

Result content

Result unit %

Formula R1=

100*(H[Hydroquinone]-

Q[2])*C/m

Constant C=M/(1000*z)

M M[Gold]

z z[Gold]

Decimal places 1

Result limits No

Record statistics No

Extra statistical func. No

Send to buffer No

011 Calculation R2

Result content

Result unit carat

Formula R2=

24*(H[Hydroquinone]-Q[2])*C/m

Constant C=M/(1000*z)

M M[Gold]

z z[Gold]

Decimal places 1

Result limits No



Send to buffer No

012 Record

Summary No

Results Per sample

Raw results Per sample

Table of meas. values All titration functions

Sample data No

Resource data No

E - V All titration functions

dE/dV - V All titration functions

log dE/dV - V No

d2E/dV2 - V No

BETA – V No

E - t No

V - t No

dV/dt - t No

T – t No

E – V & dE/dV – V No

V – t & dV/dt – t No

Method No

Series data No

Condition No

013 End of sample


Titration of Gold -Au(I)- in a Standard Cyanide Solution Content determination of gold Au(I) in an aqueous solution of potassium dicyanoaurate KAu(CN)2 by precipitation of AgAu(CN)2 with silver nitrate. The titration is monitored with a combined silver ring sensor.

Preparation and Procedures CAUTION: Cyanide is toxic!

A too low pH value i.e. below pH 3 leads to the formation of HCN gas which is toxic. Thus, work in a fume hood, use safety googles and wear gloves.

Standard solution:

- Weigh approx. 1.5 g potassium dicyanoaurate KAu(CN)2 in 250 mL volumetric flask. (This application: 1.46739 g).

- Fill up to the mark with deionized water.

Titration:

- Pipette 5 mL of the above standard solution into a titration beaker.

- Add 50 mL deionized water.

- Adjust to pH 3-5 by carefully adding 1 mol/L nitric acid (or more concentrated, if necessary).

- The titration is performed using a DM141 silver ring electrode with silver nitrate 0.1 mol/l as a titrant.

Remarks

- The method was developed on a DL40 titrator and was adapted for DL5x, DL7x , G20 and Titration Excellence titrators.

Literature:

- DL40 application no. 8121, 1981 (customer sample)

- METTLER TOLEDO Application Brochure No. 28 “electronics and Electroplating Applications”, 2007 (only available as PDF-file).

- Vogel's textbook of quantitative inorganic analysis, 4th edition, Longman Group Limited, 1978.

- See Application M525 (Brochure 18) for the standardization of silver nitrate.

Sample Standard solution, KAu(CN)2

5 mL c(KAu(CN)2) = approx. 6 g/L


Chemicals 50 mL deionized water 0.1 mol/L HNO3

Titrant Silver nitrate, c(AgNO3) = 0.1 mol/L

Standard Sodium chloride, NaCl See e.g. M525

Indication DMi141-SC (Ag ring) combined metal sensor

Chemistry With Au(I): Ag+ + Au(CN)2

- → AgAu(CN)2

Also possible with Au(III):

Ag+ + Au(CN)4- → AgAu(CN)4

Calculation Content (g/L):

R = Q*C/m

C = M/z

Waste disposal

HNO3: Neutralization with NaOH Gold, silver: Filtrate solution, special waste

CAUTION: Cyanide is toxic!

Author, Version

MSG Anachem, 1981 Revised February 2010/C. De Caro


Instruments - DL40 MemoTitrator - METTLER TOLEDO Balance, e.g. XS205

Other titrators: This method can be also run with the T50/T70/T90 Titration Excellence and G20 Compact Titrator, and with the DL5x and DL7x instruments (with major changes).

Accessories - 10 mL DV1010 burettes - Glass titration beaker ME-101446 - Printer

Results Au+ n Comments

Mean value 3.9978 g/L 5 DL40 application no. 8121

Theoretical 4.0134 g/L 1.46739 g KAu(CN)2 in 250 mL

Content deionized water

M(KAu(CN)2) = 288.07

Rel. standard 0.07 %

deviation srel

Titration curve




Not available

Comments

• Monovalent gold ( Au(I) ), which is present as dicyanoaurate anion in solution, is precipitated as AgAu(CN)2 during titration with silver nitrate:


• A similar precipitation reaction takes place when determining trivalent gold, i.e. Au3+ with silver nitrate as a titrant:


• Nitric acid 0.1mol/L is added to increase the steepness of the potential jump at the equivalence point.

• If the standard solution should contain chloride, then the latter can be determined by continuing the analysis until a second equivalence point is evaluated. This is due to the precipitation of silver chloride in the sample solution.

• Gold electroplating baths contain free cyanide ions. Interference from free cyanide ions can be avoided by adjusting the pH to 5-6 using 30-40% formaldehyde solution. Generally, this solution has a pH value between 3 and 4. After a waiting time of 15-20 minutes, the titration can be started. The addition of formaldehyde leads to the formation of cyanohydrin compounds RR’C(OH)CN according to the general reaction between an aldehyde RHC=O or a ketone (RR’C=O) and free cyanide ions:

RHC=O + HCN → RHC(OH)CN

With formaldehyde, H2C=O, the reaction can be given as:

H2C=O + HCN → H2C(OH)CN


Method T50/T70/T90 Titration Excellence:

001 Title


Compatible with T50/T70/T90

ID m207

Title Au solution

Author Mettler Toledo

Date/Time 01.02.2010 15:00:00

Modified at 01.02.2010 15:00:10

Modified by Administrator

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 KAu(CN)2

Entry type Fixed volume

Volume 5.0 mL

Density 1.0 g/mL


Temperature 25.0°C


Type Manual stand


004 Stir

Speed 35%

Duration 10 s

Condition No


Titrant

Titrant AgNO3


Sensor

Type mV

Sensor DMi141-SC

Unit mV



Stir

Speed 35%

Predispense

Mode None

Waiting time 0 s

Control

Control User


dE (set value) 8 mV

dV (min) 0.02 mL

dV (max) 0.2 mL

Mode Equilibrium controlled

dE 0.5 mV

dt 2 s

t (min) 5 s

t (max) 30 s


Procedure Standard

Threshold 800

Tendency Positive

Ranges 0


Termination

At Vmax 10 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQPs 1


criteria No

006 Calculation R1

Result Au Content

Result unit g/L

Formula R1 = Q*C/m

Constant C= M/z

M M[Gold]

z z[Gold]

Decimal places 4

Result limits No

Record statistics Yes

Extra statistical

functions No

Send to buffer No

Condition No

007 End of sample

008 Report

Summary Yes

...

DL5x Titrators:

Title

Method ID ............................m207

Title ................................Au solution

Date/time ............................01-02-2010 15:00

Sample

Sample ID ............................KAu(CN)2

Entry type ...........................Fixed volume

Volume [mL] ..........................5.0

Molar mass M .........................196.97

Equivalent number z .................1

Titration stand ......................Stand 1

Temperature sensor ...................Manual

Stir

Speed [%] ............................50

Time [s] .............................10

EQP titration

Titrant/Sensor

Titrant ..............................AgNO3

Concentration [mol/L] ................0.1

Sensor ...............................DM141-SC

Unit of meas. .......................mV

Predispensing ........................No

Titrant addition .....................Dynamic

dE(set) [mV] .........................8.0

dV(min) [mL] .........................0.02 dV(max) [mL] .........................0.2 Measure mode ........................Equilibrium

.....................................controlled

dE [mV] ..............................0.5

dt [s] ...............................2.0

t(min) [s] ...........................5.0

t(max) [s] ...........................30.0

Recognition

Threshold ............................800

Steepest jump only ..................No

Range ................................No

Tendency .............................Positive

Termination

at maximum volume [mL] ...............10.0

at potential .........................No

at slope .............................No

after number EQPs ....................Yes

n = .................................1

comb. termination criteria ..........No

Evaluation

Procedure ............................Standard

Potential 1 ..........................No

Potential 2 ..........................No

Stop for reevaluation ................Yes

Condition ...........................neq=0

Calculation

Formula .............................R=Q*C/m

Constant .............................C=M/z

Decimal places .......................4

Result unit ..........................g/L

Result name ..........................Au content

Statistics ...........................Yes

Calculation

Formula ..............................R2=VEQ

Constant .............................

Decimal places .......................3

Result unit ..........................mL

Result name ..........................Consumption

Statistics ...........................Yes

Calculation

Formula ..............................

Constant .............................

Decimal places .......................0

Result unit ..........................

Result name ..........................

Statistics ...........................No

Report

Output ..............................Printer

Results ..............................No

All results ..........................Yes

Raw results ..........................No

Table of measured values .............Yes

Sample data ..........................No

E - V curve ..........................Yes

dE/dV - V curve ......................Yes d2E/dV2 - V curve ....................No

log dE/dV - V curve ..................No E - t curve ..........................No

V - t curve ..........................No

dV/dt - t curve ......................No


Standardization of Cerium Sulfate vs. Hydroquinone Titer determination of cerium sulfate by redox titration of hydroquinone aqueous solution. The result –a relative factor- is used in applications M298 (standardization hydroquinone and cerium sulfate vs. gold) and M299 (determination of gold).

Preparation and Procedures Titration:

- Place an empty glass titration beaker on the manual titration stand

- 40 mL HCl 0.1 mol/l will be pumped in automatically

- 1.5 mL hydroquinone will be dispensed

- The sample will be titrated with cerium(IV) sulfate 0.01 mol/L using a DMi140-SC sensor.

Hydroquinone solution, c(1/2 C6H6O2) = 0.05 mol/L:

- Weigh 2.753 g hydroquinone in a glass beaker

- Transfer with deionized water into a 1 L measuring flask

- Add approx. 900 mL deionized water

- Add 10 mL H2SO4 96%

- Fill up to the mark with deionized water

Cerium sulfate solution, c(Ce(SO4)2) = 0.01 mol/L:

- Pipette 50.0 mL of cerium sulfate 0.1 mol/L (e.g. Merck 1.09092.1000) in a 500 mL volumetric flask.


- Add 10 mL H2SO4 96% and gently mix it


The cerium(IV) sulfate solution is unstable because a precipitation occurs. It is recommended to prepare a new solution every 2 days.

The hydroquinone solution is stable but it is recommended to prepare a new solution every 10 days

Remarks

Theoretical consumption: 1 mL hydroquinone, c(1/2 C6H6O2) = 0.05 mol/L, corresponds to 5 mL cerium(IV) sulfate, c(Ce(SO4)2)= 0.01 mol/L. Literature: METTLER TOLEDO Application Brochure “Gold and Silver”, ME-724613, 04/1994.

Sample Hydroquinone, C6H6O2

c (1/2 C6H6O2) = 0.05 mol/L 1.5 mL

Compound Hydroquinone, C6H6O2

M(C6H6O2) = 110.11 g/mol, z = 2

Chemicals 0.1 mol/L hydrochloric acid, HCl

Titrant Cerium(IV) sulfate, Ce(SO4)2 c(Ce(SO4)2) = 0.01 mol/L

Standard --

Indication DMi140-SC (Pt ring) combined redox sensor

Chemistry C6H6O2 + 2 Ce4+ →

C6H4O2 + 2 Ce3+ + 2 H+

Calculation R1 = VENDDi*0.05/(VEQ*c) C1 = 1 Result is stored as auxiliary value: H[Cerium sulfate] = Mean [R1]

Waste disposal

Hydroquinone: Evaporate solution,special waste Cerium: Precipitate with NaOH, filtrate, special waste

Author, Version

Claudia Schreiner, MSG Anachem, April 2007


Instruments - T50/70/T90 Titration Excellence with LabX titration - XS205 Balance

Other titrators: This method can be also run with the DL5x and DL7x instruments (with method changes).

Accessories - 2 x 10 mL DV1010 burettes - Additional dosing unit ME-51109030 - Glass titration beaker ME-101446 - SP250 Peristaltic pump ME-5108016

Results Start time: 22.03.2007 Sample Data Note / ID Sample size No. 1/6 Hydroquinone 1.5 mL No. 2/6 Hydroquinone 1.5 mL No. 3/6 Hydroquinone 1.5 mL No. 4/6 Hydroquinone 1.5 mL No. 5/6 Hydroquinone 1.5 mL No. 6/6 Hydroquinone 1.5 mL Results Note / ID Rx Result Unit No. 1/6 Hydroquinone R1= 0.9828 -- No. 2/6 Hydroquinone R1= 0.9822 -- No. 3/6 Hydroquinone R1= 0.9829 -- No. 4/6 Hydroquinone R1= 0.9832 -- No. 5/6 Hydroquinone R1= 0.9833 -- No. 6/6 Hydroquinone R1= 0.9836 -- Statistics Rx Name n Mean Value Unit s srel[%] R1 Factor 6 0.9830 -- 0.0005 0.05

Titration curve

sample 1/5




Volume lncrement Signal Change 1. Derivative Time mL mL mV mV mV/mL s 0.000 NaN 381.7 NaN NaN 0 2.857 2.857 429.0 47.3 NaN 14 4.286 1.429 440.1 11.1 NaN 24 5.000 0.714 446.0 5.9 NaN 30 5.200 0.200 448.7 2.7 NaN 39 5.400 0.200 451.4 2.7 9.01 43 5.600 0.200 452.6 1.2 9.83 46 5.800 0.200 454.2 1.6 9.60 50 6.000 0.200 456.0 1.8 8.75 53 6.200 0.200 458.1 2.1 9.99 56 6.400 0.200 460.2 2.1 11.79 59 6.600 0.200 462.9 2.7 9.55 62 6.800 0.200 465.7 2.8 5.89 66 7.000 0.200 469.6 3.9 21.83 70 7.200 0.200 474.2 4.6 115.11 76 7.400 0.200 480.4 6.2 404.51 83 7.600 0.200 502.5 22.1 1244.86 86 7.626 0.026 558.2 55.7 1962.45 117 7.631 0.005 661.1 102.9 2970.64 147 EQP1 (1) 7.631 NaN 664.6 NaN NaN NaN 7.636 0.005 725.9 64.8 2577.51 177 . . . . . . . . . . . . . . . . . . 8.270 0.172 842.8 8.9 49.62 301 8.464 0.194 850.7 7.9 37.38 305 8.664 0.200 857.6 6.9 29.70 308 8.664 0.200 862.5 4.9 25.05 313 9.064 0.200 867.8 5.3 21.28 316 9.264 0.200 871.4 3.6 NaN 320 9.464 0.200 875.0 3.6 NaN 323 9.664 0.200 878.5 3.5 NaN 326 9.864 0.200 881.2 2.7 NaN 329 10.000 0.136 883.1 1.9 NaN 332 sample1/5

Comments

To determine pure gold or its content in alloys the precipitation method with hydroquinone has been selected. Most of the associated metals do not interfere with the determination.

As the precipitation of gold is too slow to execute a direct titration with hydroquinone, an excess of hydroquinone is added to the dissolved gold. The excess is titrated back with cerium(IV) sulfate:

1. Oxidation of gold: Gold is oxidized to Au3+ by aqua regia (conc. HCl/conc. HNO3 3:1 v/v).

2. Precipitation of gold: Au3+ is reduced by excess hydroquinone and precipitates, and quinone is formed.

Au3+ + 3 C6H6O2 = 2 Au + 3 C6H4O2 + 6 H+

3. Excess hydroquinone is oxidized by cerium(IV) sulfate (back titration):

2 Ce4+ + C6H6O2 = C6H4O2 + 2 Ce3+ + 2 H+

It has been shown (Ref. 1) that copper, iron, zinc, nickel, platinum and palladium do not interfere. We have found in our own work that silver does not interfere.

Application M298 (Standardization of hydroquinone and cerium(IV) sulfate vs. gold) and M299 (Determination of gold) complete the whole analysis for the gold content titration.

The complete analysis sequence consists of the following steps: 1) M297 2) M298 3) M299 Literature: 1. S.C. Soundar Rajan and N. Appala Raju, “Titrimetric Determination of Gold by Precipitation with

Hydroquinone”, Talanta 22 (1975), pp. 185-189. 2. A. Chow, “The Stability of Gold Solutions”, Talanta 18 (1971), pp. 453-456.


Method 001 Title



ID m297

Title Factor cerium sulfate


Date/Time 05.04.2007 10:39:52

Modified at 05.04.2007 10:39:52

Modified by admin

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Hydroquinone


Volume 1.5 mL

Density 1.0 g/mL


Temperature 25.0°C

Entry Arbitrary


Type Manual stand


004 Pump


Volume [mL] 40

Condition No

005 Dispense

Titrant ½ Hydroquinone


Volume 1.5

Dosing rate 60.0 mL/min

Condition No

006 Stir

Speed 35%

Duration 10 s

Condition No


Titrant

Titrant Cerium sulfate


Sensor

Type mV

Sensor DM140-SC

Unit mV



Stir

Speed 35%

Predispense

Mode Volume

Volume 5

Waiting time 5 s

Control

Control User


dE (set value) 8 mV

dV (min) 0.005 mL

dV (max) 0.2 mL


dE 0.5 mV

dt 2 s

t (min) 3 s

t (max) 30 s


Procedure Standard

Threshold 500

Tendency Positive

Ranges 0


Termination

At Vmax 10 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number EPQs 1


criteria No

Accompanying stating

Accompanying stating No

Condition

Condition No

008 Calculation R1

Result Factor

Result unit -

Formula R1=VENDDi*0.05/(VEQ*c)

Constant C= 1

M M[None]

z z[None]

Decimal places 5

Result limits No


Extra statistical

functions No

Send to buffer No

Condition No

009 End of sample

010 Auxiliary value

Name Cerium sulfate

Formula H= Mean[R1]

Limits No

Condition No


Standardization of Hydroquinone and Cerium Sulfate with Pure Gold Titer determination of hydroquinone by means of pure gold as a standard. Gold ions are reduced to elemental gold after addition of hydroquinone. Excess hydroquinone is determined by redox titration with cerium sulfate. The result is used in M299 (determination of gold).


Gold dissolution:

- Weigh 20-30 mg gold sample in a glass beaker

- Add 5 mL HCl 32% and 1.5 mL HNO3 65%. Never use prepared aqua regia, it is unstable!

- Dissolve it on a heating plate (110-130°C).


- Repeat addition of 5 mL HCl 32%.

- Repeat again evaporation to almost dryness, but never evaporate to complete dryness.

- Rinse the beaker walls with a small amount (max. 10 mL) of deionized water or 5 mL 32% HCl. Let the sample cool down before starting the titration.

Titration:


- 30 mL HCl 0.1 mol/l will be pumped in automatically.

- Hydroquinone (1/2 C6H6O2) will be added automatically. Note: The volume to be dispensed is calculated in the method to achieve an optimum titrant consumption of 7 mL.

- The back titration is performed using a DMi140-SC redox sensor with cerium(IV) sulfate 0.01 mol/l.

Remarks



- 1 mL hydroquinone, c(1/2 C6H6O2)=0.05 mol/L corresponds to 5 mL cerium sulfate, c(Ce(SO4)2)= 0.01 mol/L.


Sample Pure gold, 20-30 mg


Chemicals 32% hydrochloric acid, HCl 65% nitric acid, HNO3 0.1 mol/L hydrochloric acid, HCl 96% sulfuric acid, H2SO4

Titrant Hydroquinone, C6H6O2 c(1/2 C6H6O2) = 0.05 mol/L Cerium sulfate, Ce(SO4)2 c(Ce(SO4)2) = 0.01 mol/L

Standard --

Indication DMi140-SC (Pt ring) combined redox sensor

Chemistry Reduction with hydroquinone: 2 Au3+ + 3 C6H6O2 → 2 Au + 6 H+ + 3 C6H4O2

Titration of excess hydroquinone: C6H6O2 + 2 Ce4+ → C6H4O2 + 2 Ce3+ + 2 H+

Calculation Predispensing Ce(SO4)2 : R1=QENDDi/(H[Cerium sulfate]*0.01)-C C=m*1523*H[Cerium sulfate] Titer hydroquinone vs. gold: R2=C/(QENDDi-VEQ*c*H[Cerium sulfate]) C=(m*1000*z)/M Titer cerium(IV) sulfatevs. gold: R3=Mean[R2]*H[Cerium sulfate] C=1

Waste disposal


Author, Version



Instruments - T70/T90 Titration Excellence with LabX titration - XS205 Balance

Other titrators: This method can be also run with the DL55/DL58 and DL70ES/DL77 titrators with method changes). T50, DL50 Graphix, DL53 and DL67 require manual operations.


Results Start time: 27.03.2007

Sample Data Note / ID Sample size

No. 1/5 Fluka Gold 0.03064 g





Results Note / ID Rx Result Unit

No. 1/5 Fluka Gold R2= 1.0004 --

R3= 0.9892 --

No. 2/5 Fluka Gold R2= 0.9857 --

R3= 0.9747 --

No. 3/5 Fluka Gold R2= 0.9981 --

R3= 0.9870 --

No. 4/5 Fluka Gold R2= 1.0036 --

R3= 0.9924 --

No. 5/5 Fluka Gold R2= 0.9994 --

R3= 0.9872 -–

Statistics

Rx Name n Mean Value Unit s srel[%]

R1 Titer 1/2 Hydroquinone vs gold 5 0.9974 -- 0.007 0.69

R2 Titer Cerium(IV) sulfatevs gold 5 0.9861 -- 0.007 0.68

Titration curve

sample 1/5



Table of measured values Volume Increment Signal 1st Derivative Time Temperature mL mL mV mV/mL s °C 0.000 NaN 479.000 NaN 0.000 25.000 3.220 3.220 486.800 NaN 10.000 25.000 4.829 1.609 496.900 NaN 17.000 25.000 5.634 0.805 503.700 NaN 23.000 25.000 5.834 0.200 505.600 NaN 38.000 25.000 6.034 0.200 508.400 24.310 42.000 25.000 6.234 0.200 511.700 31.110 47.000 25.000 6.434 0.200 516.100 40.000 52.000 25.000 6.634 0.200 522.700 63.190 57.000 25.000 6.834 0.200 536.400 157.890 64.000 25.000 6.903 0.069 545.500 251.360 67.000 25.000 6.934 0.031 553.600 370.210 72.000 25.000 6.950 0.016 558.400 504.270 76.000 25.000 6.973 0.023 572.500 917.050 86.000 25.000 6.979 0.006 578.300 1112.690 91.000 25.000 6.934 0.005 585.400 1107.130 101.000 25.000 6.909 0.005 593.700 1396.460 114.000 25.000 6.994 0.005 597.300 1581.450 120.000 25.000 7.007 0.013 623.100 1905.420 147.000 25.000 7.012 0.005 632.700 2022.650 160.000 25.000 7.017 0.005 638.700 1994.060 166.000 25.000 EQPI 7.017 NaN 639.300 1953.990 NaN NaN 7.028 0.011 665.600 1507.130 192.000 25.000 7.033 0.005 673.200 1333.730 200.000 25.000 7.041 0.000 684.100 1134.510 211.000 25.000 7.049 0.000 690.500 NaN 210.000 25.000 7.063 0.014 697.300 NaN 222.000 25.000 7.092 0.029 708.600 NaN 227.000 25.000 7.117 0.025 717.000 NaN 232.000 25.000 7.141 0.024 726.000 NaN 236.000 25.000 sample1/5

Comments

Principle: To determine pure gold or its content in alloys the precipitation method with hydroquinone has been selected. Most of the associated metals do not interfere with the determination. As the precipitation of gold is too slow to execute a direct titration with hydroquinone, an excess of hydroquinone is added to the dissolved gold. The excess is titrated back with cerium sulfate:

1. Oxidation of gold: Gold is oxidized to Au3+ by aqua regia (conc. HCl/conc. HNO3 3:1 v/v). 2. Precipitation of gold:

Au3+ is reduced by excess hydroquinone and precipitates, and quinone is formed. Au3+ + 3 C6H6O2 → 2 Au + 3 C6H4O2 + 6 H+

3. Excess hydroquinone is oxidized by cerium (IV) sulfate (back titration): 2 Ce4+ + C6H6O2 → C6H4O2 + 2 Ce3+ + 2 H+


Application M297 (Factor cerium(IV) sulfate vs. hydroquinone) and M299 (Determination of gold) complete the whole analysis for the gold content titration.

The complete analysis sequence consists of the following steps: 1) M297 2) M298 3) M299

Accuracy: The accuracy which can be obtained by these methods depends on:

1. the weighing and handling procedures e.g. use a balance with high resolution and tweezers 2. the care with which the gold sample is prepared and dissolved. 3. the amount of gold taken. 4. the accuracy of titration method and titrator.

Maintenance of the electrode: We recommend to always clean the electrode after 6 gold titrations because gold contaminates the platinum ring by forming a thin layer: Place it for two minutes in aqua regia and rinse thoroughly with deionized water (See also leaflet of the DMi140-SC electrode).

Literature: 1. S.C. Soundar Rajan and N. Appala Raju, “Titrimetric Determination of Gold by Precipitation with


Principle of titration method



006 Dispense (Hydroquinone) A known excess of hydroquinone is dispensed depending on the size of the gold standard. The optimum titrant consumption for back-titration with cerium(IV) sulfateis set to approx. 7 mL. The predispensing volume VENDDi of hydroquinone solution is calculated accordingly.

008 Calculation (Amount of cerium(IV) sulfateto be predispensed) A predispensing of 70% of cerium(IV) sulfateis used to speed up the titration time. It is calculated based on the predispensing of hydroquinone (QENDDi) and on the gold standard amount.

009 Titration (EQP, back- titration with cerium sulfate) Here the predispensing of cerium(IV) sulfatetitrant is calculated from the result of function 008 Calculation.

010 Calculation (Titer ½ C6H6O2 vs. gold) The titer of hydroquinone, ½ C6H6O2, is determined using pure gold as standard. It is calculated and stored as auxiliary value H[Titer ½ C6H6O2 vs gold] in function 013.

011 Calculation (Titer Ce(SO4)2 vs. gold) The auxiliary value H[Cerium sulfate] is obtained by standardization of cerium(IV) sulfatewith hydroquinone (M297). The titer of cerium sulfate, Ce(SO4)2, must be now referred to pure gold. This is determined in function 011 Calculation. It is stored as auxiliary value H[Titer Ce(SO4)2 vs gold] in function 014.

013 Auxiliary value: H[Titer ½ C6H6O2 vs. gold] = Mean[R2]




Summary of the method parameters:

Parameter Symbol Unit Predispense Cerium sulfate VENDDi [mL]

Predispense Cerium sulfate QENDDi [mmol]

Consumption Cerium sulfate Q [mmol]

Equivalent number of gold z 3

Size of gold sample [g] m 0.02-0.03

Molar mass of gold [g/mol] M 196.967

Titrant Cerium sulfate [mol/L] c (Ce(SO4)2) 0.01

Titrant Hydroquinone [mo/L] c (½ C6H6O2) 0.05

Preparation of the reagents

Hydroquinone solution, c(1/2 C6H6O2) = 0.05 mol/L:

- Weigh 2.753 g Hydroquinone in a glass beaker

- Transfer with deionized water into a 1 L measuring flask


- Add 10 mL H2SO4 96%


Cerium(IV) sulfatesolution, c(Ce(SO4)2) = 0.01 mol/L:

- Pipette 50.0 mL of cerium(IV) sulfate0.1 mol/L (e.g. Merck 1.09092.1000) in a 500 mL volumetric flask


- Add 10 mL H2SO4 96% and gently mix it


Note:

• The cerium(IV) sulfatesolution is unstable because a precipitation occurs. We recommend preparing a new solution every 2 days.

• The hydroquinone solution is stable but we recommend preparing a new solution every 10 days.

• Gold sample: Solid gold is dissolved in strong oxidizing acid solution and evaporated to almost dryness (never to complete dryness). If necessary, this procedure has to be repeated until no yellow fumes (nitrous gases) are formed anymore. For the sample sizes used (20-30 mg), the procedure was repeated once.


Method 001 Title



ID m298

Title Factor Hydroquinone Solution


Date/Time 08.03.2007 15:01:02

Modified at 05.04.2007 10:42:46

Modified by admin

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Gold

Entry type Weight

Lower limit 0.02 g

Upper limit 0.03 g

Density 1.0 g/mL


Temperature 25.0°C

Entry Arbitrary


Type Manual stand


004 Pump


Volume [mL] 30

Condition No

005 Stir

Speed 50%

Duration 5 s

Condition No

006 Dispense

Titrant ½ C6H6O2


Volume 304.6*m+1.4*H[Cerium sulfate]


Condition No

007 Stir

Speed 50%

Duration 180 s

Condition No

008 Calculation R1

Result Predispense cerium sulfate

Result unit mL

Formula R1=

QENDDi/(H[Cerium sulfate]*0.01)-C

Constant C= m*1523*H[Cerium sulfate] M M[None]

z z[None]

Decimal places 3

Result limits No


Extra statistical

functions No

Send to buffer No

Condition No


Titrant

Titrant Ce(SO4)2


Sensor

Type mV

Sensor DM140-SC

Unit mV



Stir

Speed 40%

Predispense

Mode Volume

Volume 0.7*R1

Waiting time 10 s

Control

Control User


dE (set value) 8 mV

dV (min) 0.005 mL

dV (max) 0.2 mL


dE 0.5 mV

dt 2 s

t (min) 3 s

t (max) 30 s


Procedure Standard

Threshold 200

Tendency Positive

Ranges 0


Termination

At Vmax 15 mL

At potential No

At slope No

After number of

recognized EQPs Yes


criteria No



Condition

Condition No

010 Calculation R2

Result Titer ½ C6H6O2 vs. gold

Result unit -

Formula R2=

C/(QENDDi-VEQ*c*H[Cerium sulfate])

Constant C= (m*z*1000)/M

M M[Gold]

z z[Gold]

Decimal places 5

Result limits No


Extra statistical

functions No

Send to buffer No

Condition No

011 Calculation R3

Result Titer Ce(SO4)2 vs. gold

Result unit -

Formula R3=Mean[R2]*H[Cerium sulfate]

Constant C= 1

M M[None]

z z[None]

Decimal places 5

Result limits No


Extra statistical

functions No

Send to buffer No

Condition No

012 End of sample

013 Auxiliary value

Name Titer 1/2 C6H6O2 vs. gold

Formula H= Mean[R2]

Limits No

Condition No

014 Auxiliary value

Name Titer Ce(SO4)2 vs. gold

Formula H= Mean[R3]

Limits No

Condition No


Determination of Gold Content determination of gold by reduction of gold ions in solution to elemental gold after addition of hydroquinone. Excess hydroquinone is determined by redox titration with cerium(IV) sulfate. Applications M297 and M298 describe the standardization of the used titrants.


Gold dissolution:

- Weigh 20-30 mg gold sample in a glass beaker

- Add 5 mL HCl 32% and 1.5 mL HNO3 65%.

- Dissolve it on a heating plate (110-130°C).


- Repeat addition of 5 mL HCl 32%.

- Repeat evaporation to almost dryness, but never evaporate to complete dryness.

- Rinse the beaker walls with a small amount (max. 10 mL) of deionized water or 5 mL 32% HCl. Let the sample cool down before starting titration.

Titration:


- 30 mL HCl 0.1 mol/l is pumped in automatically.

- Hydroquinone (1/2 C6H6O2) will be added automatically. Note: The volume to be dispensed is calculated in the method to achieve an optimum titrant consumption of 6 mL.

- The back titration is performed using a DMi140-SC redox sensor with cerium(IV) sulfate 0.01 mol/l.

Remarks

1. Pure gold is used as a standard.



- 1 mL hydroquinone c c(1/2 C6H6O2)=0.05 mol/L corresponds to 5 mL cerium sulfate, c(Ce(SO4)2)= 0.01 mol/L.


Sample Gold, 20-30 mg


Chemicals 32% hydrochloric acid, HCl 65% nitric acid, HNO3 0.1 mol/L hydrochloric acid, HCl

Titrant Hydroquinone, C6H6O2 c(1/2 C6H6O2) = 0.05 mol/L Cerium sulfate, Ce(SO4)2 c(Ce(SO4)2) = 0.01 mol/L

Standard See M297 and M298 for standardization of titrants


Chemistry Reduction with hydroquinone: 2Au3+ + 3C6H6O2 → 2Au + 6H+ + 3C6H4O2

Titration of excess hydroquinone: C6H6O2 + 2Ce4+ → C6H4O2 + 2Ce3+ + 2H+

Calculation Content (%): R1= 100*(QENDDi*H[Titer 1/2 C6H6O2 vs gold]-Q*H[Titer Ce(SO4)2 vs gold])*C

C = M/(m*z*1000) Content (carat): R2= 24*(QENDi*H[Titer ½ C6H6O2 vs gold]-Q*H[Titer Ce(SO4)2 vs gold])*C

C = M/(m*z*1000)

Waste disposal


Author, Version



Instruments - T90 Titration Excellence with LabX titration - XS205 Balance

Other titrators: This method can be also run with the T50 and T70 Titration Excellence (if the logical conditions are eliminated), and with the DL5x and DL7x instruments (with major changes).


Results Start time: 27.03.2007

Sample Data Note / ID Sample size Correction factor

No. 1/3 Gold 995 0.01968 g 100

No. 2/3 Gold 995 0.02061 g 100

No. 3/3 Gold 995 0.02673 g 100

Results Note / ID Rx Result Unit

No. 1/3 Gold 995 R1= 99.958 %

R2= 23.990 Carat

No. 2/3 Gold 995 R1= 98.819 %

R2= 23.717 Carat

No. 3/3 Gold 995 R1= 99.161 %

R2= 23.799 Carat

Statistics

Rx Name n Mean Value Unit s srel[%]

R1 Purity 3 99.31 % 0.59 0.6

R2 Carat 3 23.84 Carat 0.14 0.6

Titration curve

sample 1/3



Table of measured values Volume lncrement Signal Change 1. Derivative Time mL mL mV mV mV/mL s 0 NaN 471.9 NaN NaN 0 0.005 0.005 471.7 -0.2 NaN 3 0.01 0.005 471.7 0 NaN 6 0.022 0.012 471.7 0 NaN 9 0.054 0.032 471.7 0 NaN 12 0.131 0.077 471.9 0.2 1.9 15 0.325 0.194 472.4 0.5 2.68 18 ... ... ... ... ... ... 3.925 0.2 487.2 1.2 7.02 73 4.125 0.2 488.7 1.5 7.67 76 4.325 0.2 490.5 1.8 8.48 79 4.525 0.2 492.2 1.7 9.47 82 4.725 0.2 494.2 2 10.59 86 4.925 0.2 496.6 2.4 10.94 89 5.125 0.2 499.4 2.8 0.34 92 5.325 0.2 502.9 3.5 11.09 96 5.525 0.2 507.3 4.4 73.22 99 5.725 0.2 513.8 6.5 264.75 102 5.925 0.2 527.1 13.3 797.13 105 5.998 0.073 596.2 69.1 1429.05 135 6.0024 NaN 644.4 NaN NaN NaN 6.003 0.005 651 54.8 1748.07 166 6.008 0.005 694.4 43.4 1315.63 196 6.013 0.005 720.7 26.3 1739.01 226 . . . . . . . . . . . . . . . . . . 13.915 0.2 887.4 0.7 2.85 451 14.115 0.2 887.8 0.4 2.8 454 14.315 0.2 888.4 0.6 NaN 457 14.515 0.2 889 0.6 NaN 460 14.715 0.2 889.4 0.4 NaN 463 14.915 0.2 890.4 1 NaN 466 15.0 0.085 890.4 0 NaN 469 sample 1/3

Comments

Principle: To determine pure gold or its content in alloys the precipitation method with hydroquinone has been selected. Most of the associated metals do not interfere with the determination. As the precipitation of gold is too slow to execute a direct titration with hydroquinone, an excess of hydroquinone is added to the dissolved gold. The excess is titrated back with cerium sulfate:

1. Oxidation of gold: Gold is oxidized to Au3+ by aqua regia (conc. HCl:conc. HNO3 3:1 v/v). 2. Precipitation of gold:

Au3+ is reduced by excess hydroquinone and precipitates, and quinone is formed. Au3+ + 3 C6H6O2 → 2 Au + 3 C6H4O2 + 6 H+

3. Excess hydroquinone is oxidized by cerium(IV) sulfate (back titration): 2 Ce4+ + C6H6O2 → C6H4O2 + 2 Ce3+ + 2 H+


Application M297 (Factor cerium(IV) sulfate vs. hydroquinone) and M298 (Titer of hydroquinone and cerium(IV) sulfate with pure gold) describe the standardization of the used reagents. The complete analysis sequence involves the following steps: 1) M297 2) M298 3) M299

Accuracy: The accuracy which can be obtained by these methods depends on:

1. the weighing and handling procedures e.g. use a balance with high resolution and tweezers 2. the care with which the gold sample is prepared and dissolved. 3. the amount of gold taken. 4. the accuracy of titration method and titrator.

Maintenance of the electrode: We recommend to always clean the electrode after 6 gold titrations because gold contaminates the platinum ring by forming a thin layer: Place it for two minutes in aqua regia and rinse thoroughly with deionized water (See also leaflet of the DMi140-SC sensor).

Literature: 1. S.C. Soundar Rajan and N. Appala Raju, “Titrimetric Determination of Gold by Precipitation with



002 Sample The known gold concentration (in % or in carat) is entered as factor f of the sample in method function 002 SAMPLE. It will be used in the function 004 (or 005) AUXILIARY VALUE. 004 Auxiliary Value / 005 Auxiliary Value In this function the factor of the method function 002 Sample will be used to calculate the H[Fraction Gold] depending on the content of the alloy. 008 Dispense Hydroquinone An excess of hydroquinone is dispensed depending on the amount of gold sample and concentration. Furthermore, the dispensed volume (VENDDi) is calculated for an optimum titrant consumption of 6 mL cerium(IV) sulfate for the back titration.



011 Calculation Purity (percent) The concentration is calculated in percent. 012 Calculation Purity (carat) The concentration is calculated in carat.

Parameter Symbol Unit Predispense Cerium sulfate VENDDi [mL] Predispense Cerium sulfate QENDDi [mmol] Consumption Cerium sulfate Q [mmol] Equivalent number of gold z 3 Size of gold sample m [g] Molar mass of gold [g/mol] M 196.967 Titrant Cerium(IV) sulfate[mol/L] c (Ce(SO4)2) 0.01 Titrant Hydroquinone [mo/L] c (½ C6H6O2) 0.05 Correction factor f % or carat gold of the

sample



Method 001 Title


Compatible with T90

ID m299

Title Gold content


Date/Time 21.03.2007 16:02:39

Modified at 05.04.2007 10:41:10


Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Gold 995

Entry type Weight

Lower limit 0.02 g

Upper limit 0.03 g

Density 1.0 g/mL


Temperature 25.0°C

Entry Arbitrary


Type Manual stand


004 Auxiliary value

Name Fraction Gold

Formula H= f/24

Limits No

Condition Yes

Formula f<=24

005 Auxiliary value

Name Fraction Gold

Formula H= f/100

Limits No

Condition Yes

Formula f>24ANDf<=100

006 Pump


Volume [mL] 30

Condition No

007 Stir

Speed 50%

Duration 5 s

Condition No

008 Dispense

Titrant ½ C6H6O2


Volume 1.2*H[Titer Ce(SO4)2 vs. gold]

+304.6*m*H[Fraction Gold]/H[Titer

½ C6H6O2 vs. gold]


Condition No

009 Stir

Speed 50%

Duration 180 s

Condition No


Titrant

Titrant Ce(SO4)2


Sensor

Type mV

Sensor DM140-SC

Unit mV



Stir

Speed 40%

Predispense

Mode None

Waiting time 0 s

Control

Control User


dE (set value) 8 mV

dV (min) 0.005 mL

dV (max) 0.2 mL


dE 0.5 mV

dt 2 s

t (min) 3 s

t (max) 30 s


Procedure Standard

Threshold 200

Tendency Positive

Ranges 0


Termination

At Vmax 15 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQPs 1


criteria No



Condition

Condition No

011 Calculation R1

Result Purity

Result unit %

Formula R1=

100*(QENDDi*H[Titer 1/2 C6H6O2 vs.

gold]-Q*H[Titer Ce(SO4)2 vs.

gold])*C

Constant C= M/(m*z*1000)

M M[Gold]

z z[Gold]

Decimal places 3

Result limits No


Extra statistical

functions No

Send to buffer No

Condition No

012 Calculation R2

Result Purity in Carat

Result unit Carat

Formula R2=

24*(QENDDi*H[Titer 1/2 C6H6O2 vs

gold]-Q*H[Titer Ce(SO4)2 vs.

gold])*C

Constant C= M/(m*z*1000)

M M[Gold]

z z[Gold]

Decimal places 3

Result limits No


Extra statistical

functions No

Send to buffer No

Condition No

013 End of sample

Note:

1. The method can be easily modified to be run on T50 and

T70 Titration Excellence instruments:

delete method functions 004 and 005 AUXILIARY VALUE

since they contain logical conditions.

2. If the gold content is known (% or carat), then it can

be entered as a factor in the method function SAMPLE. In

this way, it is possible to calculate the most

appropriate predispense for an optimum consumption of 6

mL.


Determination of Silver in Silver Alloys Content determination of silver Ag(I) in silver alloys by precipitation silver chloride AgCl with sodium chloride as a titrant. The titration is monitored with a combined silver ring electrode.

Preparation and Procedures CAUTION: Work in a fume hood. Concentrated nitric acid is dangerous. Use safety googles, wear gloves and a lab coat.

Sample preparation:

- Clean the sample with acetone and let it dry – use tweezers.

- Weigh in a sample corresponding to approx. 40 mg Ag and read to ±0.01 mg; then put it in the glass titration beaker.

- Add 3 mL of 33% HNO3 and warm up to 60 °C in a water bath until the sample is completely dissolved.

- In case of an impure sample add 1 mL of H2SO4 to improve the dissolution.

- Let the sample cool down to room temperature. This procedure is a prerequisite to achieve high precision.

Titration:

- Add 50 mL deionized water.

- Start titration. The titration is performed using a DM141-SC silver ring electrode with sodium chloride 0.1 mol/l.

Remarks

- The method parameters have been developed and optimized for this application. It may be necessary to adapt the method to your sample.

- Rinse the electrode after each sample. If necessary, clean the metal ring of the electrode with a paper tissue at the end of each sample series.

- High speed: The method was also streamlined to fast titrations. The titration takes less than 2 min.

Literature: - METTLER TOLEDO Application Brochure No. 28

“Electronics and Electroplating Applications”, 2007 (only available as PDF-file).


Sample Silver alloys, approx. 0.05 g

Compound Silver, Ag M = 107.868; z = 1

Chemicals 3 mL 33% nitric acid, HNO3

50 mL deionized water (conc. sulfuric acid)

Titrant Sodium chloride, NaCl, c(NaCl) = 0.1 mol/L

Standard Silver nitrate, AgNO3 See e.g. M536

Indication DMi141-SC (Ag ring) combined metal electrode

Chemistry Precipitation of silver chloride: Ag+ + Cl- → AgCl

Calculation Content (%):

R = Q*C/m

C = M/(10*z)

Waste disposal

Silver precipitate can be separated (filtration). The filtrated solution is neutralized with NaOH.

Author, Version

Susanne Wahlen, MSG Anachem, May 2010


Instruments - T50/70/90 Titration Excellence - XS205 Balance This method can also be run with the G20 Compact Titrator (with minor adjustments)

Accessories - 2 x 10 mL DV1010 burette - 1 x additional dosing unit - Glass titration beaker ME-101446 - LabX titration pro

Results METTLER TOLEDO T90

DL90 Silver

Method: MS112B Silver sample 04.06.2010 15:14:54

Results

Series start time 04.06.2010 15:15:25

No. Note / ID Start time Rx Result Unit Name

1/8 C6: Silver Sample 04.06.2010 15:15:25 R1 = 3.447 mL Consumption

R2 = 98.077(2)% Silver Content


R2 = 98.912 % Silver Content


R2 = 98.907 % Silver content











Statistics: n = 7 R2 = 98.962 ± 0.051% s = 0.300 srel: 0.051% (2) excluded

Titration curve

Sample 1/8




Volume Increment Signal Change 1st deriv. Time mL mL mV mV mV/mL min:s -------------------------------------------------------------------------------------------- 0 NaN 415.2 NaN NaN 0 1.143 1.143 403.6 -11.6 NaN 4 1.7145 0.5715 396.3 -7.3 NaN 7 2 0.2855 391.5 -4.8 NaN 10 2.4 0.4 382.8 -8.7 NaN 24 2.8 0.4 370.3 -12.5 -50.52 27 3.01 0.21 360.4 -9.9 -74.7 30 3.1355 0.1255 352.6 -7.8 -101.94 34 3.244 0.1085 342.3 -10.3 -143.19 37 3.3075 0.0635 333.7 -8.6 -195.41 40 3.353 0.0455 326.7 -7 -263.64 43 3.4045 0.0515 313 -13.7 -396.33 46 3.424 0.0195 305.2 -7.8 -496.98 49 3.439 0.015 297.4 -7.8 -578.52 52 3.452 0.013 289.7 -7.7 -655 55 3.4655 0.0135 279.2 -10.5 -740.15 58 3.4745 0.009 271.2 -8 -833.6 62 EQP1 3.47658 NaN 269.4 NaN -833.98 NaN 3.4835 0.009 263.4 -7.8 -816.06 65 3.494 0.0105 254.2 -9.2 -724.07 68 3.5045 0.0105 246.1 -8.1 -643.32 71 3.518 0.0135 237.9 -8.2 -570.06 74 3.5365 0.0185 229.4 -8.5 NaN 77 3.562 0.0255 220.4 -9 NaN 80 3.596 0.034 212 -8.4 NaN 83 3.6465 0.0505 203 -9 NaN 86 3.7185 0.072 194.6 -8.4 NaN 89

Comments

- To further improve accuracy and precision, it is recommended to use a microbalance.

- Furthermore, the sample has to be cleaned using e.g. ethanol, acetone and additional suitable organic solvents to eliminate impurities such as e.g. fatty residues.

- The sample has to be handled using cleaned tweezers in order to avoid any contact with the fingers (fatty residues).

- In this application, the sample i.e. the digested silver solution was dispensed with an additional dosing unit in order to achieve a higher repeatability (m = 7 mL).


Method 001 Title Type General titration Compatible with T50 / T70 / T90 ID MS112B Title Silver Sample Author wahlen Date/Time 03.06.2010 13:44:05 Modified at 04.06.2010 15:14:54 Modified by wahlen Protect No SOP None 002 Sample Number of IDs 1 ID 1 Silver wire Entry type Fixed weight Weight [g] 0.037837 Density [g/mL] 1.0 Correction factor 1.0 Temperature [°C] 25.0 Entry Arbitrary 003 Titration stand (Manual stand) Type Manual Stand Titration stand Manual Stand 1 004 Stir Speed [%] 40 Duration [s] 1 Condition No 005 Dispense (normal)[1] Titrant Silver sample Concentration 99.9 Volume [mL] 7.0 Dosing rate [mL/min] 60.0 Condition No 006 Stir Speed [%] 40 Duration [s] 10 Condition No 007 Titration (EQP) [1] Titrant Titrant NaCl Concentration [mol/L] 0.1 Sensor Type mV Sensor DM141-SC Unit mV Temperature acquisition Temperature acquisition No Stir Speed [%] 30 Predispense Mode Volume Volume [mL] 2 Waiting time 10 Control Control Normal Mode Precipitation Show parameters Yes Titrant addition Dynamic dE (set value) [mV] 9.0 dV (min) [mL] 0.008 dV (max) [mL] 0.4 Mode Equilibrium controlled dE [mV] 0.5 dt [s] 1.0 t (min) [s] 3.0 t (max) [s] 30 Evaluation and recognition Procedure Standard Threshold 400.0 Tendency None Ranges 0 Add. EQP criteria No Termination At Vmax [mL] 10.0 At potential No At slope No After number of recognized EQPs Yes Number of EQPs 1 Combined termination criteria No Accompanying stating Accompanying stating No Condition Condition No 008 Calculation R1 Result Consumption Result unit mL Formula R1=VEQ Constant C= 1 M M[None] z z[None] Decimal places 3

Result limits No Record statistics No Extra statistical func. No Send to buffer No Condition No 009 Calculation R2 Result Silver Content Result unit % Formula R2=Q*C/m Constant C= M/(10*z) M M[Silver] z z[Silver] Decimal places 3 Result limits No Record statistics Yes Extra statistical func. No Send to buffer No Condition No 010 Record Summary No

Results Per sample


Table of meas. values Last titration function

Sample data No

Resource data No

E - V Last titration function

dE/dV - V Last titration function

log dE/dV - V No

d2E/dV2 - V No

BETA – V No

E - t No

V - t No

dV/dt - t No

T – t No



Method No

Series data No

Condition No

011 End of sample


Determination of Free Cyanide in a Cyanidic Silver Bath Free cyanide is precipitated by addition of silver nitrate forming silver dicyanoargentate. The titration is indicated by a silver ring sensor.


A too low pH value i.e. below pH 3 leads to the formation of HCN gas which is toxic. Thus, work in a fume hood, use safety googles and wear gloves.

Sample preparation:

- 1 mL silver bath is diluted with 50 mL deionized water.

Titration:

- Start titration. The titration is performed using a DM141-SC silver ring electrode with silver nitrate 0.1 mol/l.

Remarks

- The method was developed on a DL67 titrator and has been adapted for T50/T70/T90 Titration Excellence and G20 Compact Titrator.

Literature:

- METTLER TOLEDO Application Brochure No. 28 “Electronics and Electroplating Applications”, 2007 (only available as PDF-file).

- Application note, DL25 Application Brochure "Petroleum and electroplating", ME-51724627.


- D.A. Skoog, D.M. West, "Fundamentals of Analytical Chemistry", Holt, Rinehart, and Winston, 1969.


Sample Silver bath, 1 mL

Compound Potassium cyanide, KCN M = 65.12, z = 1

Chemicals 50 mL deionized water,

Titrant Silver nitrate, c(AgNO3) = 0.1 mol/L

Standard Sodium chloride, NaCl See e.g. M525

Indication DMi141-SC (Ag ring) combined metal sensor

Chemistry Ag+ + 2 CN- → Ag(CN)2-

First silver excess (precipitate): Ag+ + Ag(CN)2

- → Ag[Ag(CN)2]

Calculation Content (g/L):

R = Q*C/m

C = M*2

The content is expressed as KCN g/L

Waste disposal

Cyanide waste. CAUTION: Cyanide is toxic!

Author, Version

Application laboratory, MT-D, 1994 Rev. February 2010 / C. De Caro


Instruments - DL67 Version 3.1 - Balance, e.g. XS205 - Sample changer, e.g. Rondo20

Other titrators: This method can also be run with the T50/T70/T90 Titration Excellence and G20 Compact Titrator (delete “Rinse” function), and with the DL5x and DL7x instruments.

Accessories - 10 mL DV1010 burettes - PP titration beaker ME-101974 - SP250 Peristaltic pump ME-51108016 - Printer

Results Method BL20 KCN im cy.Ag.Bad 17-02-1994 10:46 User Measured 24-02-1994 14:49 RESULTS No ID1 ID2 Sample amount and results 1/1 1.0 mL Fixed volume U R1 = 110.34 g/L KCN R2 = 8.49 mL Consumption 1/2 1.0 mL Fixed volume U R1 = 111.64 g/L KCN R2 = 8.59 mL Consumption 1/3 1.0 mL Fixed volume U R1 = 114.09 g/L KCN R2 = 8.78 mL Consumption STATISTICS Number results R1 n = 3 Mean value x = 112.02 g/L KCN

Titration curve



Table of measured values Not available

Comments

• A soluble complex Ag(CN)2- is first formed by the reaction between silver and cyanide ion:

Ag+ + 2 CN- → Ag(CN)2–

• As long as free cyanide is still present, the solution remains clear, but the first excess of silver causes formation of a white precipitate silver dicyanoargentate that indicates the endpoint:

Ag+ + Ag(CN)2- → Ag[Ag(CN)2]

• Since 1 mole of Ag ions reacts with two moles of cyanide ions, the factor 2 is taken into account in the calculation (see constant C).

• T50/70/90 Titration Excellence –G20 Compact Titrator No titration method function “Rinse” can be defined when working with the G20 Compact Titrator. Thus, function 006 “Rinse” has to be deleted in order to run the analysis on the G20 titrator.


Method DL7x Titrators:

Title

Method ID ........................... BL20

Title ............................... KCN im cy.Ag.Bad

Date/time ........................... 17-02-1994 10:46

Sample

Number samples ...................... 20

Titration stand ..................... ST20 1

Entry type .......................... Fixed volume

Volume [mL]....................... 1.0

ID1 .................................

Molar mass M ........................ 65.12


Temperatur sensor ................... Manual

Stir

Speed [%] ........................... 50

Time [s] ............................ 10

Titration

Titrant ............................. AgNO3

Concentration [mol/L] ............... 0.1

Sensor .............................. DM141-SC

Unit of meas. ...................... mV

Titration mode ...................... EQP

Predispensing 1................... to volume

Volume [mL] .................... 1.0

Titrant addition .................... DYN

dE(set) [mV] ................... 8.0

Limits dV ...................... Absolute

dV(min) [mL]................. 0.05

dV(max) [mL]................. 0.5

Measure mode ....................... EQU

dE [mV] ........................ 0.5

dt [s] ......................... 1.0

t(min) [s] ..................... 3.0

t(max) [s] ..................... 30.0

Threshold ........................... 50.0

Maximum volume [mL] ................. 30.0

Termination after n EQPs ............ Yes

n = ........................... 1

Evaluation procedure ................ Standard

Rinse

Auxiliary reagent ................... H2O

Volume [mL] ......................... 10.0

Calculation

Result name ......................... KCN

Formula ............................ R=Q*C/m

Constant ............................ C=M*2

Result unit ......................... g/L

Decimal places ...................... 2

Calculation

Result name ......................... Comnsumption

Formula ............................ R2=VEQ

Constant ............................

Result unit ......................... mL

Decimal places ...................... 2

Statistics

Ri (i=index) ........................ R1

Standard deviation s ............... Yes

Rel. standard deviation srel ........ Yes

Outlier test ........................ Yes

Record

Output unit ......................... Printer

All results ......................... Yes

Titration Excellence:

001 Title



ID m196

Title KCN im cy.Ag.Bad


Date/Time 01.02.2010 08:00:00

Modified at 01.02.2010 08:00:10


Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 KCN in cyanidic Ag bath


Volume 1.0 mL

Density 1.0 g/mL


Temperature 25.0°C

Entry Arbitrary

003 Titration stand (Rondo/Tower A)

Type Rondo/Tower A

Titration stand Rondo60/1A

004 Stir

Speed 50%

Duration 10 s

Condition No


Titrant

Titrant AgNO3


Sensor

Type mV

Sensor DMi141-SC

Unit mV



Stir

Speed 35%

Predispense

Mode Volume

Volume 1.0

Waiting time 10 s

Control

Control User



dV(min) 0.05 mL

dV(max) 0.5 mL


dE 0.5 mV

dt 1 s

t (min) 3 s

t (max) 30 s


Procedure Standard

Threshold 50

Tendency Positive

Ranges 0


Termination

At Vmax 30 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQPs 1

006 Rinse

Auxiliary reagent Water

Rinse cycles 1

Vol. Per cycle 10 ml

Position Current position

007 Calculation R1

Result KCN in cyan. Ag-bath

Result unit g/L

Formula R1=Q*C/m

Constant C= M*2

M M[KCN]

z z[KCN]

Decimal places 2

Result limits No


. . .

008 End of sample

009 Report

Summary Yes

. . .


Determination of Free Cyanide and Silver Free cyanide and silver are precipitated as silver dicyanoargentate by addition of silver nitrate; the titration is indicated by a silver ring sensor.

Preparation and Procedures CAUTION: Cyanide is very toxic!

A too low pH value i.e. below pH 3 leads to the formation of HCN gas which is toxic. Thus, work only in a fume hood, use safety goggles, wear gloves and a lab coat.

1) The titer determination of silver nitrate is performed using sodium chloride (NaCl) as a primary standard. Since small amounts of salt cannot be weighed in exactly, it is recommended to prepare an aqueous solution of NaCl, and then to add the standard with a pipette.

2) 1-2 mL of silver bath is pipetted in a plastic titration beaker, 50 mL deionized water is automatically added with the diaphragm pump of the Rondo sample changer.

3) The titration is performed using a DMi141-SC silver ring electrode with ½ AgNO3 0.2 mol/l.

4) During titration, the pH is maintained at 12.5 with NaOH using the parameter “Accompanying stating”.

Note: The parameters have been optimized for this specific sample. It may be necessary to adapt the method to your sample.

Remarks

Literature:

- METTLER TOLEDO Application Brochure No. 28 “Electronics and Electroplating Applications”, 2007 (only available as PDF-file).

- Application M196, “Determination of Free Cyanide in a Cyanidic Silver Bath”.


- D.A. Skoog, D.M. West, "Fundamentals of Analytical Chemistry", Holt, Rinehart, and Winston, 1969.


Sample Silver cyanidic bath with approx. 8-10 g/L CN- and approx. 20-25 g/L Ag+, 0.5-2 mL

Compound Cyanide, CN- M = 26.02 g/mol, z = 1 Silver, Ag+

M = 107.868 g/mol, z = 2

Chemicals 50 mL deionized water

Titrant Silver nitrate, AgNO3 c(½ AgNO3) = 0.2 mol/L 1 mL≙ 2.60 mg CN-, 1 mL≙5.39 mg Ag+ Sodium hydroxide, NaOH, C(NaOH) = 1 mol/L

Standard Sodium chloride, NaCl

Indication DMi141-SC (Ag ring) DGi112-Pro

Chemistry Ag+ + 2 CN- → Ag(CN)2-

First silver excess (precipitate): Ag+ + Ag(CN)2

- → Ag[Ag(CN)2]

Calculation R1 = Q[2]*C/m C = M/z Content expressed as CN- g/L R2 = (QEX[2]+Q[3]-Q[2])*C/m C = M/z Content expressed as Ag+ in g/L

Waste disposal

Cyanide waste, pH >12 CAUTION: Cyanide is toxic!

Author, Version

Claudia Schreiner, MSG Anachem June 2010


Instruments - T90 Titration Excellence - Balance, e.g. XS205 - Rondo 20 Sample Changer with PowerShower™ and diaphragm pump

Accessories - 2 x 10 mL DV1010 burettes - 1 additional dosing Unit - PP titration beaker ME-101974 - SP250 Peristaltic pump ME-51108016

Results All results Sample Cyanide and Silver Bath (1/6) R1 (Cyanide content) 9.96 R2 (Silver content) 22.69 Sample Cyanide and Silver Bath (2/6) R1 (Cyanide content) 9.89 R2 (Silver content) 22.82 Sample Cyanide and Silver Bath (3/6) R1 (Cyanide content) 9.86 R2 (Silver content) 22.80 Sample Cyanide and Silver Bath (4/6) R1 (Cyanide content) 9.85 R2 (Silver content) 22.82 Sample Cyanide and Silver Bath (5/6) R1 (Cyanide content) 9.73 R2 (Silver content) 23.18 Sample Cyanide and Silver Bath (6/6) R1 (Cyanide content) 9.74 R2 (Silver content) 23.05 Statistics R1 Cyanide content R2 Silver content Samples 6 Samples 6 Mean 9.84 Mean 22.89 s 0.09 s 0.18 srel 0.9% srel 0.80%

Titration curve

Cyanide Silver




Values Cyanide determination

Volume Increment Signal Change 1st deriv. Time Temperature mL mL mV mV mV/mL s °C 0.000 NaN -197.6 NaN NaN 0 25 0.050 0.05 -167.1 30.5 NaN 10 25 0.100 0.05 -168.1 -1.0 NaN 20 25 0.225 0.13 -168.2 -0.1 NaN 30 25 0.425 0.20 -168.2 0.0 NaN 40 25 0.625 0.20 -168.3 -0.1 -2.6 50 25 0.825 0.20 -168.0 0.3 1.8 61 25 1.025 0.20 -167.6 0.4 2.2 71 25 1.225 0.20 -167.1 0.5 2.6 81 25 1.425 0.20 -166.5 0.6 3.0 91 25 . . . . . . . . . . . . . . . . . . . . . 7.806 0.05 -79.7 5.0 104.6 474 25 7.856 0.05 -73.4 6.3 184.4 484 25 7.906 0.05 -65.3 8.1 308.6 494 25 7.956 0.05 -53.1 12.2 286.5 504 25

EQP1 7.985 NaN -40.5 NaN 325.3 NaN NaN 8.006 0.05 -31.5 21.6 221.5 516 25 8.056 0.05 2.1 33.6 193.3 539 25 8.106 0.05 5.6 3.5 177.2 549 25 8.231 0.13 8.1 2.5 NaN 559 25 8.431 0.20 9.2 1.1 NaN 570 25 8.631 0.20 9.6 0.4 NaN 580 25 8.831 0.20 9.9 0.3 NaN 590 25 9.031 0.20 10.1 0.2 NaN 600 25

Values Silver determination

Volume Increment Signal Change 1st deriv. Time Temperature mL mL mV mV mV/mL s °C 0 NaN -197.6 NaN NaN 0 25 0.05 0.05 -167.1 30.5 NaN 10 25 0.1 0.05 -168.1 -1 NaN 20 25 0.225 0.125 -168.2 -0.1 NaN 30 25 0.425 0.2 -168.2 0 NaN 40 25 0.625 0.2 -168.3 -0.1 -2.63 50 25 0.825 0.2 -168 0.3 1.77 61 25 . . . . . . . . . . . . . . . . . . . . . 7.8555 0.05 -73.4 6.3 184.36 484 25 7.9055 0.05 -65.3 8.1 308.59 494 25 7.9555 0.05 -53.1 12.2 286.5 504 25 EQP1 7.984614 NaN -40.5 NaN 325.27 NaN NaN 8.0055 0.05 -31.5 21.6 221.47 516 25 8.0555 0.05 2.1 33.6 193.33 539 25 8.1055 0.05 5.6 3.5 177.24 549 25 8.2305 0.125 8.1 2.5 NaN 559 25 8.4305 0.2 9.2 1.1 NaN 570 25 8.6305 0.2 9.6 0.4 NaN 580 25 8.8305 0.2 9.9 0.3 NaN 590 25 9.0305 0.2 10.1 0.2 NaN 600 25


Comments

Reaction

A soluble complex Ag(CN)2- is first formed by the reaction between silver and cyanide ion:

Ag+ + 2 CN- → Ag(CN)2–

As long as free cyanide is still present, the solution remains clear, but the first excess of silver

causes formation of the white precipitate silver dicyanoargentate that indicates the endpoint:

Ag+ + Ag(CN)2- → Ag[Ag(CN)2]

Method

The titration of cyanide and silver is a two step procedure. The first step (Titration [2]) determines the cyanide content by using an asymmetric evaluation of the curve.

The second step (Titration [3]) determines the silver content using a standard evaluation of the curve.

Method 001 Title


Compatible with T90

ID CSM196

Title Cyanide and Silver Bath


Date/Time 01.06.2010 14:55:13

Modified at 01.06.2010 16:59:58


Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Silver bath

Entry type Volume

Lower limit 0.0 mL

Upper limit 5.0 mL

Volume 1.0 mL

Density 1.0 g/mL


Temperature 25.0°C

Entry Arbitrary


Type Rondo/Tower A


004 Pump

Auxiliary reagent WATER

Volume 50 mL

Condition No

005 Stir

Speed 35%

Duration 10 s

Condition No

006 Measure

Sensor

Type pH

Sensor DG112-Pro

Unit pH



Stir

Speed 35%

Acquisition of measured values

Acquisition Equilibrium

dE 0.5 mV

dt 1 s

t (min) 10 s

t (max) 30

Mean value No

Condition

Condition No

007 Calculation R1

Result pH

Result unit

Formula R1 = E

Constant C= M/z

M M[None]

z z[None]

Decimal places 2

Result limits No


Extra statistical funct. No

Send to buffer No

Condition No

008 Titration (EP) [1]

Titrant

Titrant NaOH


Sensor

Type pH

Sensor DG112-Pro

Unit pH



Stir

Speed 35%

Predispense

Mode None

Waiting time 10 s

Control

Control Absolute

Tendency None

End point value 12.5 pH

Control band 0.5 pH

Dosing rate (max) 10 mL/min


Termination

At EP Yes

Termination delay 10 s

At Vmax 20 mL

Max Time 600s



Condition

Condition Yes

Formula R1<12.3



Titrant

Titrant ½ AgNO3


Sensor

Type mV

Sensor DM141-SC

Unit mV



Stir

Speed 35%

Predispense

Mode Volume

Volume 0.5

Waiting time 10 s

Control

Control User



dV(min) 0.005 mL

dV(max) 0.1 mL


dE 0.5 mV

dt 2 s

t (min) 10 s

t (max) 30 s


Procedure Asymmetric

Threshold 200

Tendency Positive

Ranges 1

Lower limit -400 mV

Upper limit 150 mV


Termination

At Vmax 5 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQPs 1


criteria No


Accompanying stating Yes

Titrant

Titrant NaOH


Continuous addition No

Sensor

Type pH

Name DG112-Pro

Unit pH

Pretitration

Pretitration No

Predispense

Mode None

Wait time 0 s

Control

Set potential 12.5 pH

Control band 0.5 pH

Tendency Positive


Dosing rate (min) 10 µL/min

Monitoring

Monitoring No

Condition

Condition No


Titrant

Titrant ½ AgNO3


Sensor

Type mV

Sensor DM141-SC

Unit mV



Stir

Speed 35%

Predispense

Mode None

Waiting time 0 s

Control

Control User



dV(min) 0.05 mL

dV(max) 0.2 mL


dE 0.5 mV

dt 2 s

t (min) 10 s

t (max) 30 s


Procedure Standard

Threshold 100

Tendency Positive

Ranges 0


Termination

At Vmax 10 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQPs 1


Accompanying stating Yes

Titrant

Titrant NaOH


Continuous addition No

Sensor

Type pH

Name DG112-Pro

Unit pH

Pretitration

Pretitration No

Predispense

Mode None

Wait time 0 s

Control

Set potential 12.5 pH

Control band 0.5 pH

Tendency Positive


Dosing rate (min) 10 µL/min

Monitoring

Monitoring No

Condition

Condition No

011 Calculation R2

Result Cyanide content

Result unit g/L

Formula R2 = Q[2]*C/m

Constant C= M/z

M M[Cyanide]

z z[Cyanide]

Decimal places 2

Result limits No



Send to buffer No

Condition No

012 Calculation R3

Result Silver content

Result unit g/L

Formula R3 = (QEX[2]+Q[3]-Q[2])*C/m

Constant C= M/z

M M[Silver]

z z[Silver]

Decimal places 2

Result limits No



Send to buffer No

Condition No

013 Rinse

Auxiliary reagent WATER

Rinse cycles 3

Vol. Per cycle 20 ml

Position Current sample

Drain Yes

Drain pump DRAIN

Condition No

014 Conditioning

Type Fix

Interval 1

Position Conditioning beaker

Time 30 s

Speed 30 %

Condition No

015 End of sample


Determination of Palladium Content Palladium(II) was determined by potentiometric titration with hexadecylpyridinium chloride (HDPCl) using a surfactant sensitive electrode in combination with a reference electrode.

Preparation and Procedures Hexadecylpyridinium chloride (HDPCl, 0.02 mol/L): - 7.16020 g HDPCl monohydrate is cautiously

dissolved (avoid foam formation) in 200-300 mL deionized water in a 1 L volumetric flask.

- The flask is slowly filled up with deionized water. - Note: HDPCl is also called cetylpyridinium

chloride (CPC). Sodium dodecylsulfate (SDS, 0.004 mol/L): - 1.15352 g is added into a 1 L volumetric flask,

which is slowly filled up with deionized water to avoid the formation of foam.

Palladium chloride, PdCl2 (0.01 mol/L): - 0.18230 g is added in a 100 mL volumetric flask. - The flask is filled with approx. 80 mL mixed

solution (0.5 mol/L NaCl in 0.5 mol/L HCl). - PdCl2 dissolves slowly while stirring. After

complete dissolution, fill up to the mark by adding further mixed solution.

Titer determination of HDPCl: - 10 mL SDS (0.004 mol/L) was added to 50 mL

deionized water and subsequently titrated with HDPCl.

Remarks

Sample preparation: - 5 mL 0.01 mol/L PdCl2 solution is added into a

titration beaker. - 50 mL mixed solution (0.5 mol/L NaCl in 0.5

mol/L HCl) is automatically added by an additional dosing unit.

- Subsequently, 5 mL ethanol is added to ensure complete dissolution of PdCl2, and also to reduce foaming as well as flocculation during titration.

Calculations: For all calculations, the actual concentrations calculated on the basis of the actual sample mass have been used (see preparation and procedures). A recovery of 101.983% for Pd(II) was obtained.

Sample Palladium chloride, PdCl2 c(PdCl2) = 0.01 mol/L

Compound Palladium(II), Pd2+ M = 106.42 g/mol, z = 2

Chemicals - Mixed solution: 0.5 mol/L NaCl in 0.5 mol/L HCl

- Ethanol

Titrant Hexadecylpyridinium chloride HDPCl, c(HDPCl) = 0.02 mol/L

Standard Sodium dodecylsulfate (SDS) c(SDS) = 0.004 mol/L

Indication - DS800 TwoPhase surfactant sensitive sensor

-DX200 Reference half-cell

Chemistry PdCl2 + 2 C21H38NCl → [Pd(II)(C21H38N)2]Cl4

Calculation R1 = VEQ, [mL] R2 = Q*C/m C = 1/z, [mol/L], z = 2

Waste disposal

Pd(II) as aqueous heavy metal waste

Author, Version

Thomas Hitz, MSG Anachem, May 2010


Instruments - T50/T70/T90 Titration Excellence - XS205 Balance - Rondolino sample changer

Accessories - 1 additional dosing unit - 2 x 10 mL DV1010 burette - Titration beaker ME-101974 - LabX pro titration software

Results All results Method-ID m462 Sample PdCl2 (1/5) R1 (Consumption) 5.25996 mL Sample PdCl2 (2/5) R1 (Consumption) 5.23816 mL Sample PdCl2 (3/5) R1 (Consumption) 5.20766 mL Sample PdCl2 (4/5) R1 (Consumption) 5.19172 mL Sample PdCl2 (5/5) R1 (Consumption) 5.18240 mL Sample PdCl2 (1/5) R2 (Content) 0.01058 mol/L Sample PdCl2 (2/5) R2 (Content) 0.01054 mol/L Sample PdCl2 (3/5) R2 (Content) 0.01047 mol/L Sample PdCl2 (4/5) R2 (Content) 0.01044 mol/L Sample PdCl2 (5/5) R2 (Content) 0.01042 mol/L Statistics Method-ID m462 R2 Content Samples 5 Mean 0.01049 mol/L s 0.00007 mol/L srel 0.647%

Titration curve




Volume Increment Signal Change 1st deriv. Time Temperature mL mL mV mV mV/mL s °C 0 NaN 107.1 NaN NaN 0 25 2.5 2.5 122.7 15.6 NaN 13 25 2.55 0.05 120.1 -2.6 NaN 78 25 2.6 0.05 119.9 -0.2 NaN 84 25 2.65 0.05 119.9 0 NaN 89 25 2.7 0.05 119.9 0 -5.14 94 25 2.75 0.05 119.8 -0.1 2.64 99 25 2.8 0.05 119.8 0 -0.28 104 25 4.9 0.05 127.2 0.5 11.45 317 25 4.95 0.05 127.8 0.6 12.97 322 25 5 0.05 128.5 0.7 13.95 327 25 5.05 0.05 129.3 0.8 15.35 332 25 5.1 0.05 130.2 0.9 20.4 337 25 5.15 0.05 131.2 1 26.92 342 25 5.2 0.05 132.3 1.1 32.86 348 25 5.25 0.05 134.2 1.9 35.55 355 25EQP1 5.259959 NaN 134.7 NaN 35.56 NaN NaN 5.3 0.05 136.8 2.6 34.59 364 25 5.35 0.05 138.2 1.4 29.91 369 25 5.4 0.05 139.3 1.1 22.24 374 25 5.45 0.05 140 0.7 15.16 379 25 5.5 0.05 140.8 0.8 11.23 384 25 5.55 0.05 141.3 0.5 10.66 389 25 5.6 0.05 141.7 0.4 9.77 394 25 5.65 0.05 142.4 0.7 8.68 400 25 5.7 0.05 142.7 0.3 7.76 405 25 5.75 0.05 143.1 0.4 7.02 410 25

Comments

• In this application, the sample is diluted by automatically adding 50 mL NaCl/HCl solution using an additional dosing unit.

• This step can be also performed manually prior titration. In this case, the method function “Dispense” has to be deleted.


Method 001 Title



Method ID m462

Title Pd analysis

Author hitz

Date/Time 10.05.2010

Modified at 10.05.2010

Modified by hitz

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 PdCl2


Volume [mL] 5

Density [g/mL] 1.0


Temperature [°C] 25.0

003 Titration stand (Rondolino TTL)

Type Rondolino TTL

Titration stand Rondolino TTL 1

004 Dispense (normal) [1]

Titrant HCl/NaCl

Concentration [mol/L] 0.5

Volume [mL] 50

Dosing rate [mL/min] 60.0

Condition No

005 Stir

Speed [%] 30

Duration [s] 30

Condition No


Titrant

Titrant HDPCl


Sensor

Type mV

Sensor DS800

Unit mV



Stir

Speed [%] 30

Predispense

Mode Volume

Volume [mL] 2.5

Wait time [s] 60

Control

Control User


dV [mL] 0.05


dE [mV] 0.5

dt [s] 2.0

t (min)[s] 5

t (max)[s] 30.0


Procedure Standard

Threshold [mV/mL] 15

Tendency Positive

Ranges 0

Add. EQP criteria Steepest jump

Steepest jumps 1

Termination

At Vmax [mL] 7

At potential No

At slope No

After number of

recognized EQPs No


criteria No


007 Calculation R1

Result Consumption HDPCl

Result unit mL

Formula R1=VEQ

Constant C=1

M M[None]

z z[None]

Decimal places 5

Result limits No



Send to buffer No

Condition No

008 Calculation R2

Result Content Pd

Result unit mol/L

Formula R2=Q*C/m

Constant C=1/z

M M[Palladium]

z z[Palladium]

Decimal places 5

Result limits No



Send to buffer No

Condition No

009 Record

Summary No

Results Per sample


Table of meas. values All titration functions

Sample data No

Resource data No

E - V All titration functions

dE/dV - V All titration functions

log dE/dV - V No

d2E/dV2 - V No

BETA – V No

E - t No

V - t No

dV/dt - t No

T – t No



Method No

Series data No

Condition No

010 End of sample


Copper Content in Copper Mining Solutions Determination of copper content in intermediate products in copper mining. Copper is determined by iodometric titration with sodium thiosulphate as a titrant. The redox reaction is indicated by a platinum pin sensor with plastic shaft.

Preparation and Procedures CAUTION: Due to the presence of hydrofluoric acid, HF, in the solution, always work in a fume cupboard, wear gloves, safety glasses and a lab coat. • Depending on the expected concentration of

Cu2+ in the sample solution, the amount of sample is chosen in such a way that the final amount of Cu2+ in the titration vessel is ~ 0.5 mmol.

• To the sample solution, excess ammonium hydrogen fluoride (NH4)(HF2) is added for masking of Fe3+ (see ‘Chemistry’). If any Fe3+ is present freely in the solution it will interfere with the Cu2+ determination by reacting with the thiosulphate to form Fe2+.

• Enough excess of potassium iodide, KI, is added to ensure that all the Cu2+ ions present in the solution can react to form I2.

• Subsequently, the generated I2 is then titrated with sodium thiosulphate, Na2S2O3, to determine the copper content via iodometric titration.

Remarks

- Because of the presence of HF in the solution, extreme care has to be taken in handling the samples.

- Neutralize the sample to annihilate the danger from HF Before final disposal.

- In addition to masking of the Fe3+, (NH4)(HF2) also keeps the pH at a low enough value for the redox reaction to complete fully.

- Should no (NH4)(HF2) be added, please make sure to add e.g. HCl to keep the pH low enough.

Note: • The addition of (NH4)(HF2) to the sample

cannot be automated with a dosing unit as the fluoride in acidic environment would corrode the glass of the burette. A peristaltic pump can be used, indeed.

• Addition of the KI solution can be automated with an extra dosing unit, indeed.

Sample Leach solution from copper ore, e.g. Chalcopyrite (CuFeS2 ). 5 mL

Compound Copper, Cu2+, M = 63.55 g/mol, z=1

Chemicals - KI solution, 10% w/w - ammonium hydrogen

fluoride solution, (NH4)(HF2) ~0.3 M solution for excess

(add > 5 mL)

Titrant Sodium thiosulfate, Na2S2O3 c(Na2S2O3) = 0.1 M

Standard Potassium iodate, KIO3

Indication - DM240-SC - DX202 (reference)

Chemistry 2 Cu2+ + 4 I- → 2 CuI + I2 I2 + 2 S2O3

2- → 2 I- + S4O62

Fe3+ + 6 F- → [FeF6]3-

Calculation Content (g/L) R1 = Q*C/m C = M/z Content (mol/L) R2 = Q*C/m C = 1/z

Waste disposal

Neutralised HF solutions do not require special disposal. Copper and iron should be disposed as heavy metals.

Author, Version

Melanie Nijman, MSG Anachem, March 2010



Instruments - T50/T70/T90 Titration Excellence - XS205 Balance - Rondo 20 sample changer

Accessories - 2 x 10 mL DV1010 burettes - Titration beakers ME-101974 - LabX pro titration software

Results

Samples 1/6 Copper solution 5.0 mL 2/6 Copper solution 5.0 mL 3/6 Copper solution 5.0 mL 4/6 Copper solution 5.0 mL 5/6 Copper solution 5.0 mL 6/6 Copper solution 5.0 mL Results Comment / ID Rx Result Unit Name 1/6 Copper solution R1 = 6.3795 g/L Content R2 = 0.10040 mol/L Content 2/6 Copper solution R1 = 6.3862 g/L Content R2 = 0.10051 mol/L Content 3/6 Copper solution R1 = 6.3855 g/L Content R2 = 0.10050 mol/L Content 4/6 Copper solution R1 = 6.4007 g/L Content R2 = 0.10074 mol/L Content 5/6 Copper solution R1 = 6.3808 g/L Content R2 = 0.10042 mol/L Content 6/6 Copper solution R1 = 6.3790 g/L Content R2 = 0.10039 mol/L Content Statistics Rx Name n Mean value Unit s srel [%] R1 Content 6 6.3853 g/L 0.0081 0.128 R2 Content 6 0.10049 mol/L 0.00013 0.130

Titration curve


Volume Increment Signal Change 1st deriv. Time mL mL mV mV mV/mL s 0 NaN 355.9 NaN NaN 0 0.02 0.02 356 0.1 NaN 14 0.04 0.02 355.9 -0.1 NaN 17 0.09 0.05 355.8 -0.1 NaN 20 0.215 0.125 355.5 -0.3 NaN 23 0.415 0.2 354.8 -0.7 -3.16 26 0.615 0.2 354.2 -0.6 -3.54 29 0.815 0.2 353.5 -0.7 -3.65 32 1.015 0.2 352.7 -0.8 -3.83 35 1.215 0.2 351.9 -0.8 -3.92 38 1.415 0.2 351.1 -0.8 -4.01 41 1.615 0.2 350.4 -0.7 -4.17 44 1.815 0.2 349.4 -1 -4.44 47 2.015 0.2 348.6 -0.8 -4.78 50 2.215 0.2 347.6 -1 -5.17 53 2.415 0.2 346.4 -1.2 -5.57 56 2.615 0.2 345.3 -1.1 -5.98 59 2.815 0.2 344.1 -1.2 -6.51 62 3.015 0.2 342.7 -1.4 -7.09 65 3.215 0.2 341.2 -1.5 -7.99 69 3.415 0.2 339.5 -1.7 -8.94 72 3.615 0.2 337.6 -1.9 -10 75 3.815 0.2 335.3 -2.3 -11.05 79 4.015 0.2 332.7 -2.6 -11.92 83 4.215 0.2 329.8 -2.9 -16.13 86 4.415 0.2 325.7 -4.1 -25.43 90 4.615 0.2 320.3 -5.4 -44.09 94 4.815 0.2 311.5 -8.8 -85.99 99 4.9805 0.1655 296.8 -14.7 -154.76 104 5.025 0.0445 289 -7.8 -165.77 107 EQP1 5.045532 NaN 285 NaN -169.75 NaN 5.0485 0.0235 284.4 -4.6 -139.72 110 5.0845 0.036 272.5 -11.9 -163.95 114 5.1045 0.02 268.3 -4.2 -120.18 118 5.1545 0.05 257.6 -10.7 -125.93 121 5.1925 0.038 255.7 -1.9 -99.48 125 5.2875 0.095 255.3 -0.4 NaN 128 5.4875 0.2 256.7 1.4 NaN 131 5.6875 0.2 257.3 0.6 NaN 134 5.8875 0.2 256.3 -1 NaN 137 6.0875 0.2 255.1 -1.2 NaN 140

Comments

• Because of the presence of hydrofluoric acid in the sample to be titrated, no glass redox electrode can be used (e.g. DMi140-SC). Especially for these kinds of applications, the polymer redox half-cell DM240-SC sensor has been developed, which is used in this application (see picture on the right).

• This sensor consists of a platinum wire mounted into a plastic shaft.

• In addition to the DM240-SC half-cell redox sensor, the special polymer reference sensor DX202-SC is used, which is also suitable for use in HF solutions (see e.g. M366).



Method 001 Title



ID MN409

Title Copper content HF

Author Administrator

Date/Time 18.03.2010 10:20:38

Modified at 19.03.2010 13:31:07


Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Copper Solution


Volume [mL] 5.0

Density [g/mL] 1.0


Temperature [°C] 25.0°C

003 Titration stand (Rondo/TowerA)

Type Rondo/Tower A


Lid handling No

004 Stir

Speed [%] 30

Duration [s] 10

Condition No


Titrant 10% KI

Concentration 1

Volume [mL] 10


Condition No


Titrant

Titrant Na2S2O3


Sensor

Type mV

Sensor DM240-SC

Unit mV



Stir

Speed [%] 30

Predispense

Mode None

Wait time [s] 10

Control

Control User


dE (set value) [mV] 8.0

dV (min) [mL] 0.02

dV (max) [mL] 0.2


dE [mV] 1.0

dt [s] 2

t (min) [s] 3

t (max) [s] 10


Procedure Standard


Tendency None

Ranges 0


Termination

At Vmax [mL] 10.0

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQPs 1


criteria No


Condition No

007 Calculation R1

Result Content

Result unit g/L

Formula R1=Q*C/m

Constant C= M/z

M M[Copper]

z z[Copper]

Decimal places 4

Result limits No



Send to buffer No

Condition No

008 Calculation R2

Result Content

Result unit mol/L

Formula R2=Q*C/m

Constant C= 1/z

M M[None]

z z[None]

Decimal places 5

Result limits No



Send to buffer No

Condition No

009 Rinse


Rinse cycles 1

Vol. per cycle[mL] 20


Drain No

Condition No

010 Conditioning

Type Fix

Interval 1


Time [s] 10

Speed [%] 30

Condition No

011 End of sample


METTLER TOLEDO Application M459-2010 Automated Determination of Iron Content in Iron Ores

The iron content in iron ores is determined by redox titration in strong acid solution with potassium dichromate K2Cr2O7 as a titrant. The potential change is monitored by a combined platinum ring electrode.

Preparation and Procedures CAUTION: Work in a fume hood, use safety goggles and wear gloves.

Sample dissolution:

- Approximately 0.05 to 0.1 g of iron powder is accurately weighed into a glass titration beaker.

- 40 mL concentrated HCl is added. - The sample is then gently heated (70-90°C) on a

hot plate while stirring until complete iron. Let the sample cool down.

Titration: - Prior to titration with K2Cr2O7, Fe(III) has to be

reduced to Fe(II) by tin chloride, SnCl2, to yield the total iron content.

- The addition of SnCl2 can be automated by means of an endpoint titration function. Initially, the potential needs to be determined where the solution turns colorless when adding SnCl2. In this case, the endpoint was set to 120 mV.

- Add 3 mL of each concentrated phosphoric and sulfuric acid for better endpoint detection. This optimizes the reduction potential and potential interferences by Fe(III) are suppressed by its complexation with PO4

3-. - EQP: The titration by K2Cr2O7 shows two

equivalence points: The first is caused by the excess ofSnCl2 while the second EQP corresponds to the iron content.

Remarks


- SnCl2 solution (approx. 1 mol/L): 30 g SnCl2 x 2 H2O (M = 225.63) is dissolved 100 mL conc. HCl, and diluted to 200 mL with deionized water.

- Rinse the sensor after each sample. If necessary, clean the metal ring of the redox electrode with a paper tissue at the end of a sample series.

Sample Iron ores, 0.08 - 0.15 g Approx. 60% iron content

Compound Iron, Fe M = 55.85; z = 1

Chemicals Conc. hydrochloric acid, HCl

Conc. sulphuric acid, H2SO4

Conc. phosphoric acid, H3PO4

Deionized water

Titrant Potassium dichromate, K2Cr2O7 c(1/6 K2Cr2O7) = 0.1 mol/L Tin(II) chloride, SnCl2 c(SnCl2) = 1 mol/L

Standard For K2Cr2O7: (NH4)2Fe(SO4)2

Indication Combined redox Pt-sensor e.g. DMi140-SC

Chemistry Reduction to Fe(II): 2 Fe3+ + Sn2+ → 2 Fe2+ + Sn4+ Titration: 6 Fe2+ + Cr2O7

2- + 14 H+ → 6 Fe3+ + 2 Cr3+ + 7 H2O

Calculation Content • R1 = Q*C/m • C = M/(10*z)

Waste disposal

Neutralize the sample with sodium hydroxide before final disposal as special waste (Chromium).

Author, Version

Susanne Wahlen, MSG Anachem, April 2010 Revised May 2010 / C. De Caro Craig Gordon, MSG Anachem, May 2005


Instruments - T70/90 Titration Excellence (T50: Dispensing of SnCl2 solution with “Dispense” function)

- XS205 Balance - Rondo 20 Sample Changer with PowerShower™

Accessories - 2 x 10 mL DV1010 burette - 2 x 5 mL DV1005 burette - 3 x additional Dosing Units (EP/Dispense with SnCl2, dosing of H3PO4 and H2SO4) - Glass titration beaker ME-101446 - LabX titration pro

Results (T70/T90)

METTLER TOLEDO T90

T90 Fumehood

Method: MS1055 Fe(II) in Ore (Rondo) 24.03.2010 14:22:41

Results


No. Comment/ID Start time Rx Result Unit Name

1/8 Iron Ore(Greece) 24.03.2010 14:23:33 R1 = NaN mL EP Consumption

R2 = 2.881 mL 2nd EQP Consumption

R3 = 37.953(2) % Iron Content

2/8 Iron Ore(Greece) 24.03.2010 14:23:33 R1 = 0.450 mL EP Consumption


R3 = 38.692 % Iron Content






R3 = 39.126(2) % Iron Content













Statistics: n = 6 R3 = 38.380 ± 0.180% s = 0.180% srel = 0.469% (2) Excluded


Titration curve (T70/T90)

Table of measured values (T70/T90)

Volume Increment Signal Change 1st deriv. Time mL mL mV mV mV/mL min:s -------------------------------------------------------------------------------------------- 0 NaN 106.2 NaN NaN 0 0.02 0.02 113.3 7.1 NaN 5 0.04 0.02 121.8 8.5 NaN 11 0.06 0.02 128 6.2 NaN 16 0.096 0.036 136.4 8.4 NaN 21 0.141 0.045 145.4 9 193.28 27 0.1885 0.0475 152.6 7.2 167.23 33 0.2565 0.068 166.6 14 154.18 38 0.2855 0.029 168 1.4 156.61 44 0.358 0.0725 182 14 181.11 49 0.378 0.02 184 2 191.62 54 0.428 0.05 194.5 10.5 244.58 61 0.448 0.02 200.4 5.9 278.22 66 0.468 0.02 205.7 5.3 311.9 71 0.5015 0.0335 217.6 11.9 411.88 77 0.5215 0.02 225.9 8.3 495.53 82 0.5415 0.02 236.1 10.2 614.63 87 0.5615 0.02 250 13.9 704.88 94 0.5815 0.02 265.5 15.5 743.42 101 EQP1 0.58904 NaN 272.2 NaN 748.48 NaN 0.6015 0.02 283.3 17.8 742.57 108 0.6215 0.02 295.7 12.4 670.24 113 0.6415 0.02 307.5 11.8 555.57 118 0.6615 0.02 318.3 10.8 450.54 123 0.6815 0.02 327.6 9.3 386.46 129 0.702 0.0205 334.4 6.8 329.82 135 0.7355 0.0335 341.5 7.1 251.25 140 0.7935 0.058 349.8 8.3 170.45 145 0.878 0.0845 358.9 9.1 115.43 150 0.976 0.098 366.3 7.4 84.31 156 1.128 0.152 375.1 8.8 60.62 160 1.3085 0.1805 383.1 8 45.23 166 1.5425 0.234 391.2 8.1 34 171 1.837 0.2945 399.4 8.2 26.29 176 2.137 0.3 406.6 7.2 22 181 2.437 0.3 412.8 6.2 19.6 186


Instruments - DL58 with manual addition of SnCl2 solution - AT261 Balance This method can also be run with the following instruments: - DL55/DL58 (2 DV090 burettes drives) and DL70ES/77 instruments (4 DV090 burette drives) - DL50/DL53, DL67 (manual addition of SnCl2 solution, phosphoric and sulphuric acids).

Accessories - 2 x 10 mL DV1010 burettes - Glass titration beaker ME-101446 - LabX titration pro

Results (DL58)

METTLER TOLEDO DL58 V2.4

DL58 Fumehood

Method: Fe003 Iron in Iron Ore 08-Jun-05 11:46 AM

Results

Series start time 08-Jun-05 4:48 PM


1 Fe2O3 08-Jun-05 4:48 PM R1 = 1.514 mL Consumption

R3 = 12.215 mL Consumption











Statistics: 64.285 ± 0.586% , srel: 0.912%

Titration curve (DL58)


Table of measured values (DL58)

Volume Increment Signal Change 1st deriv. Time mL mL mV mV mV/mL min:s -------------------------------------------------------------------------------------------- ET1 0.0000 103.9 0:06 0.0200 0.0200 118.1 14.2 707.6 0:17 0.0400 0.0200 114.9 -3.2 -158.3 0:47 0.0600 0.0200 118.3 3.4 168.0 1:18 0.1050 0.0450 142.0 23.7 527.0 1:48 0.1250 0.0200 149.0 7.0 352.2 2:17 0.1700 0.0450 204.7 55.7 1237.8 2:30 0.1900 0.0200 221.6 16.9 846.5 2:36 EQP1 0.2100 0.0200 250.6 29.0 1447.5 2:51 0.2300 0.0200 266.9 16.3 817.4 2:59 0.2720 0.0420 290.9 24.0 570.8 3:04 0.2960 0.0240 298.7 7.8 325.8 3:10 0.3440 0.0480 310.9 12.1 253.1 3:15 0.3880 0.0440 317.9 7.0 160.1 3:21 . . . . . . . . . . . . . . . . . . 11.3680 0.0890 541.0 8.8 98.7 7:51 11.4310 0.0630 549.1 8.1 128.2 7:56 11.4810 0.0500 558.3 9.2 184.8 8:02 11.5140 0.0330 566.0 7.7 233.0 8:07 11.5420 0.0280 576.0 10.0 355.4 8:14 11.5620 0.0200 583.5 7.5 374.8 8:19 11.5820 0.0200 599.0 15.5 775.4 8:25 11.6020 0.0200 625.1 26.1 1305.4 8:32 EQP2 11.6220 0.0200 833.9 208.8 10439.2 9:02 11.6420 0.0200 838.0 4.1 206.8 9:14 11.6620 0.0200 839.6 1.6 80.8 9:19 11.6860 0.0240 841.9 2.3 96.9 9:32 11.7340 0.0480 843.4 1.5 31.0 9:39 11.7830 0.0490 843.9 0.5 10.6 9:47 11.8810 0.0980 845.8 1.9 19.1 9:53 12.0770 0.1960 847.9 2.1 10.6 10:00 12.3770 0.3000 850.0 2.1 7.1 10:06 12.6770 0.3000 852.0 2.0 6.7 10:15

Comments and Methods

Chemical reactions:

1. Fe3+ has first to be reduced to Fe2+. This is achieved by adding a concentrated solution of stannous chloride, SnCl2 according to the equation: 2 Fe3+ + Sn2+ → 2 Fe2+ + Sn4+

SnCl2 can be added manually until the solution becomes colorless, or it can be added using an endpoint titration function. The titration is stopped at the potential achieved when the solution becomes colorless.

To determine this value, it is first necessary to measure the potential after manual addition. Afterwards, this value is entered as absolute EP in the titration method.

2. Iron can be now titrated with potassium dichromate, K2Cr2O7. This titration leads to two equivalence points according to the following reactions:

- 1st EQP: Excess SnCl2 arising from the EP titration is oxidized with potassium dichromate.

3 Sn2+ + Cr2O72- + 14 H+ → 3 Sn4+ + 2 Cr3+ + 7 H2O

- 2nd EQP: Oxidation of Fe 2+ with potassium dichromate.

6 Fe2+ + Cr2O72- + 14 H+ → 6 Fe3+ + 2 Cr3+ + 7 H2O


Tx Titrator

Method MS1055 Fe(II) in Ore (Rondo)

Version 24-03-2010 14:45

001 - Title

Type ............................... General titration

Compatible with .................... T70/90

Method ID .......................... MS1055

Title .............................. Fe(II) in Ore (Rondo)

Author ............................. wahlen

Date/time .......................... 24.03.2010 11:53

Modified on ........................ 24.04.2010 14:22

Modified by ........................ wahlen

Protect ............................ No

SOP ................................ None

002 - Sample

Number of IDs ...................... 1

ID1 .............................. Iron Ore

Entry type ......................... Weight

Lower limit [g] .................. 0.08

Upper limit [g] .................. 0.15

Density [g/mL] ................... 1.0

Correction factor ................ 1.0

Temperature [°C] ................. 25

Entry ............................ Arbitrary

003 – Titration stand (Rondo/Tower A)

Type ............................... Rondo/RondoA

Titration stand .................... Rondo60/1A

Lid handling ....................... No

004 – Stir

Speed [%] .......................... 50

Duration [s] ....................... 15

Condition .......................... No

005 – Titration (EP) [1]

Titrant

Titrant .......................... SnCl2

Concentration [mol/L] ............ 1.0

Sensor

Type ............................. mV

Sensor ......................... DMi140-SC

Unit. .......................... mV

006 - Temperature acquisition

Temperature acquisition .......... No

Stir

Speed [%] ........................ 45

Predispense

Mode ............................. None

Wait time [s] .................... s

Control

Mode ............................. Absolute

Tendency ......................... Negative

End point value [mV] ............. 120

Control band [mV] ................ 350

Dosing rate (max) [mL/min] ....... 7

Dosing rate (min) [μL/min] ....... 10

Termination

At EP ............................ Yes

Termination delay [s] ............ 0

At Vmax [mL] ..................... 15.0

Max. time [s] .................... infinity


Accompanying stating ............. No

Condition

Condition ........................ No

007 - Calculation R1

Result ............................. EP Consumption

Result Unit ........................ mL

Formula ............................ R1=VEQ

Constant C= ........................ 1

M .................................. M[None]

z .................................. z[None]

Decimal places ..................... 3

Result limits ...................... No

Record statistics .................. Yes

Extra statistical functions ........ No

Send to buffer ..................... No

Condition .......................... No

008 - Stir

Speed [%] .......................... 50

Duration [s] ....................... 2

Condition .......................... No

009 – Dispense (normal) [1]

Titrant ............................ Conc H3PO4

Concentration ...................... 16

Volume [mL] ........................ 3.0

Dosing rate [mL/min] ............... 40

Condition .......................... No

010 – Dispense (normal) [2]

Titrant ............................ Conc H2SO4

Concentration ...................... 18

Volume [mL].........................3.0

Dosing rate [mL/min]................20

Condition...........................No

011 - Stir

Speed [%]...........................50

Time [s]............................15

Condition...........................No

012 – Titration (EQP) [2]

Titrant

Titrant...........................1/6 K2Cr2O7

Concentration [mol/L].............0.1

Sensor..............................DM140

Type..............................mV

Sensor..........................DMi140-SC

Unit............................mV


Temperature acquisition...........No

Stir

Speed [%].........................45

Predispense

Mode..............................None

Wait time [s].....................0

Control

Control...........................User

Titrant addition................Dynamic

dE (set value) [mV] .............8.0

dV (min) [mL] ...................0.02

dV (max) [mL] ...................0.3

Mode..............................Equilibrium controlled

dE [mV] .........................0.5

dt [s]..........................1.0

t(min)[s] .......................5

t(max)[s] .......................30


Procedure.........................Standard

Threshold [mV/mL].................150

Tendency..........................Positive

Ranges............................1

Lower limit 1 [mV]................150

Upper limit 1 [mV]................2000

Add. EQP criteria.................No

Termination

At Vmax [mL]......................10.0

At potential......................No

At slope..........................No

After number of recognized EQPs...Yes

Number of EQPs..................2

Combined termination criteria.....Yes


Accompanying stating..............No

Condition

Condition.........................No

013 – Calculation R2

Result..............................2nd EQP Consumption

Result Unit.........................mL

Formula.............................R2=VEQ2[2]

Constant C=.........................1

M...................................M[None]

z...................................z[None]

Decimal places......................3

Result limits.......................No

Record statistics...................Yes

Extra statistical functions.........No

Send to buffer......................No

Condition...........................No

014 – Calculation R3

Result..............................Iron Content

Result Unit.........................%

Formula.............................R3=Q2[2]*C/m

Constant C=.........................M/10*z)

M...................................M[Iron]

z...................................z[Iron]

Decimal places......................3

Result limits.......................No

Record statistics...................Yes

Extra statistical functions.........No

Send to buffer......................No

Condition...........................No

015 - Rinse

Auxiliary reagent...................Water Tower A

Rinse cycles........................1

Vol. per cycle [mL].................10

Position............................Current position

Drain...............................No

Condition...........................No

016- End of sample

Note: The method can be easily used with a T50 titrator:

- Delete either calculation R1 or calculation R2

- Use a “Dispense” function instead of an EP titration


DL5x Titrator

Method Fe003 Iron in Iron ore

Version 08-Jun-2005 11:46

Title

Method ID .......................... Fe003

Title .............................. Iron in Iron ore

Date/time .......................... 08-Jun-2005 11:46

Sample

Sample ID .......................... Fe2O3


Lower limit [g] ................ 0.08

Upper limit [g] ................ 0.15

Molar mass M ....................... 55.85




Stir

Speed [%] .......................... 50

Time [s] ........................... 15

EP titration

Titrant/Sensor

Titrant ........................ SnCl2

Concentration [mol/L] .......... 1.0

Sensor ......................... DM140

Unit of meas. .................. mV

Predispensing ...................... No

Titrant addition ................... Dynamic

dE(set) ........................ 8.0

dV(min) [mL] ................... 0.02

dV(max) [mL] ................... 0.15

dE [mV] ........................ 1.0

dt [s] ......................... 1.0

t(min) [s] ..................... 2.0

t(max) [s] ..................... 20.0

Endpoint

Potential[mV,pH,…] ............. 120

Tendency

Tendency ....................... Negative

Termination


Delay[s] ....................... 10

Calculation

Formula ........................... R=VEQ

Constant ...........................

Decimal places ..................... 3

Result unit ........................ mL

Result name ........................ Consumption

Statistics ........................ No

Calculation

Formula ...........................

Constant ...........................

Decimal places ..................... 0

Result unit ........................

Result name ........................ No

Statistics ........................ Yes

Report

Output unit ....................... Computer

Results ............................ No

All results ........................ No

Raw results ........................ No

Table of measured values ........... No

Sample data ........................ No

E - V curve ........................ No

dE/dV – V curve .................... No

d2E/dV2 – V curve ................... No

log dE/dV – V curve... ............. No

E – t curve ........................ No

V – t curve ........................ No

dV/dt - t curve ................... No

Instruction

Text ............................... Add 3mL of conc.

............................... phosphoric

Text ............................... acid followed by 3mL of

Text ............................... conc sulphuric acid!!!

Stir

Speed [%] .......................... 50

Time [s] ........................... 15

EQP titration

Titrant/Sensor

Titrant ........................ 1/6 K2Cr2O7


Sensor ......................... DM140

Unit of meas. .................. mV

Predispensing ...................... to volume

Volume [mL] .................... 0.2

Wait time [s] .................. 20


dE(set) ........................ 8.0

dV(min) [mL] ................... 0.02

dV(max) [mL] ....................0.3

Measure mode........................Equilibrium controlled

dE [mV] .........................0.5

dt [s] ..........................1.0

t(min) [s] ......................5.0

t(max) [s] ......................30.0

Recognition

Threshold .......................400.0

Steepest jump only ..............No

Range ...........................Yes

Limit A [mV, pH,…] ...........200

Limit B [mV, pH,…] ...........2000

Tendency ........................Positive

Termination

at maximum volume [mL] ..........30.0

at potential ....................No

at slope ........................Yes

Slope [mV, pH, …/mL] .......10.0

after number EQPs ...............Yes

n = .......................2

comb. termination criteria ......Yes

Evaluation

Procedure .......................Standard

Potential 1 ....................No

Potential 2 ....................No

Stop for reevaluation ..........No

Calculation

Formula ............................R3=VEQ2[2]

Constant............................C3=1

Decimal places......................3

Result unit.........................mL

Result name.........................Consumption

Statistics .........................No

Calculation

Formula ............................R4=Q2[2]*C4/m

Constant............................C4=M/(10*z)

Decimal places......................3

Result unit.........................%

Result name.........................Iron content

Statistics .........................Yes

Report

Output unit ........................Computer

Results.............................No

All results.........................No

Raw results.........................No

Table of measured values............No

Sample data.........................No

E - V curve.........................No

dE/dV – V curve.....................No

d2E/dV2 – V curve....................No

log dE/dV – V curve.................No

E – t curve.........................No

V – t curve.........................No

dV/dt - t curve ....................No

METTLER TOLEDO Application M622-2010 Determination of Total Iron Content of Iron Ores

The iron content in 60-65% iron ores is titrated with potassium dichromate K2Cr2O7 in strong acid solution after reduction with tin(II) and titanium(III). The potential change is monitored by a combined platinum ring redox sensor.


Sample dissolution: - 0.15-0.25 g iron ore is placed in a glass titration

beaker for dissolution. - Place sample beaker in a fume hood. - Add 1 m 10% SnCl2 with a pipette. - Add 20 mL concentrated HCl and swirl the beaker

after addition to ensure complete mixing. - Place beaker on a hot plate set at 125-150°C with

integrated magnetic stirrer. Cover it with a clean watch glass and start digestion of the ore.

- After 10-20 min, swirl beaker to break up any agglomerated particles.

- Digest for a minimum of 40 min in total. - After ore digestion, slightly tilt the beaker and add a

magnetic stirrer bar. Place beaker onto the hot plate. Set temperature to heat sample but avoid boiling. Switch stirrer on, ensuring not to loose any sample.

- While gently stirring, add dropwise 10% SnCl2 solution until the color turns into a pale straw yellow. If too much SnCl2 is added, i.e. if the solution becomes colorless, add dropwise KMnO4 solution to restore the pale yellow color.

- From now on, the sample has to be titrated within 30 min at latest.

- Add dropwise 1% TiCl3 solution until liquid turns colorless. Then add three additional drops.

- Add 5 mL 0.1 M perchloric acid (HClO4). - Wait during 5 s (heating, not boiling), then remove

from hot plate. - Add 40 mL deionized water, rinsing the inside wall of

the beaker. - The sample is ready for titration.

Titration: - Add the prepared titration beakers on the sample

changer rack. - Start titration with potassium dichromate.

Remarks


- Rinse the electrode after each sample. If necessary, clean the metal ring of the electrode with a paper tissue at the end of a sample series.

Sample Iron ores, 0.15 - 0.25 g 60-65% iron content

Compound Iron, Fe M = 55.85; z = 1

Chemicals 30-34% Hydrochloric acid, HCl

10% Stannous chloride sol., SnCl2

0.4% Potassium permanganate, KMnO4

1% Titanium trichloride, TiCl3

0.1 mol/L Perchloric acid, HClO4

Deionized water

Titrant Potassium dichromate, K2Cr2O7 c(1/6 K2Cr2O7) = 0.1 mol/L

Standard Ammonium ferrous sulfate, (NH4)2Fe(SO4)2

Indication Combined redox Pt-electrode e.g. DMi140-SC

Chemistry Reduction to Fe(II): 2 Fe3+ + Sn2+ → 2 Fe2+ + Sn4+ Titration: 2 Fe2+ + Cr2O7

2- + 14 H+ → 2 Fe3+ + 2 Cr3+ + 7 H2O

Calculation Content • R1 = Q*C/m • C = M/(10*z)

Waste disposal

Neutralize the sample with sodium hydroxide before final disposal as special waste (Chromium).

Author, Version

Li Pei, MT-China, April 1999 Revised March 2010 / C. De Caro


Instruments - DL58 Titrator - AG245 Balance This method can also be run with the G20 and T50/70/90 Titration Excellence (minor

adaptations in their method), and with the DL50/DL53/DL55, and DL67/70ES/77 titrators.

Accessories - 1 x 10 mL DV1010 burette - Glass titration beaker ME-101446 - Sample Changer with pump (e.g. Rondo20) - Printer (EPSON SC 600)

Results METTLER TOLEDO DL58 Titrator V2.0 MTCS ANA MS Application Lab Method 10150 Iron in iron ores 12-Apr-1999 16:57 Measured 13-Apr-1999 11:46 User Li Pei ALL RESULTS No. ID Sample size and results 1 Iron 0.0995 g R1 = 64.7050 % iron content 2 Iron 0.1063 g R1 = 64.7105 % iron content 3 Iron 0.1004 g R1 = 64.8998 % iron content STATISTICS Number results R1 n = 3 Mean value x = 64.7718 % iron content Standard deviation s = 0.11093 % iron content Rel. standard deviation srel = 0.171 %

Titration curve




Not available


1. This method is based on a national standard pretreatment method for the determination of total iron content in iron ores (China, GB 6730.5-86, “The chemistry analysis process for the iron ore and the capacity process for measuring the amount of the whole iron with titanium trichloride and potassium dichromate”, see also ISO 2597-1:2006, ISO 2597-2:2008, and ISO 9507:1990).

2. Samples must be analyszed within 30 min after the 2nd addition of 10% stannous chloride SnCl2 solution.

3. A sample changer is used in this method for a fully automated procedure. The method can be easily modified for manual operation: enter “Stand 1” as titration stand in the function Sample (DL5x, DL7x) or “Manual Stand” (Titration Excellence).

4. After each sample, the sensor is rinsed with deionized water by means of a peristaltic pump connected to the sample changer.

Chemical reactions:

1. During dissolution, iron is oxidized to Fe3+. In order to be titrated with potassium dichromate, Fe3+ has to be reduced to Fe2+. This is achieved by adding a concentrated solution of stannous chloride, SnCl2 according to the equation: 2 Fe3+ + Sn2+ → 2 Fe2+ + Sn4+

Excess SnCl2 is oxidized with potassium permanganate, KMnO4, according to:

5 Sn2+ + 2 MnO4- + 16 H+ → 5 Sn4+ + 2 Mn2+ + 8 H2O

In the sample all iron is present as Fe2+. However, if the prepared sample solution is exposed too long a time to air, Fe2+ is easily oxidized by oxygen to Fe3+. To avoid it, some titanium trichloride, TiCl3, is added in slight excess:

Ti3+ + Fe3+→ Fe2+ + Ti4+

Perchloric acid, HClO4, is added to neutralize excess TiCl3 .

2. Iron can be now titrated with potassium dichromate, K2Cr2O7, according to the following reaction:

6 Fe2+ + Cr2O72- + 14 H+ → 6 Fe3+ + 2 Cr3+ + 7 H2O

Literature:

1. ISO 2597-1:2006, “Iron ores -- Determination of total iron content -- Part 1: Titrimetric method after tin(II) chloride reduction”.

2. ISO 2597-2:2006, “Determination of total iron content -- Part 2: Titrimetric methods after titanium(III) chloride reduction”.

3. ISO 9507:1990, “Determination of total iron content -- Titanium(III) chloride reduction methods”

4. S. Kallmann, E. Kormanova, “Pollution-free method for the determination of iron in iron ore”, Talanta, Vol. 29(8), 1982, pp. 700-702.

5. J. Henry, R. Gelbach, “Dichromate determination of iron using silver reductor”, Ind. Eng. Chem. Anal. Ed., Vol. 16 (1), 1944, p. 49.


DL5x Titrator

Method 10150 Iron in iron ores

Version 12-Apr-1999 16:57

Title

Method ID .......................... 10150

Title .............................. Iron in iron ores

Date/time .......................... 12-Apr-1999 16:57

Sample

Sample ID .......................... Iron


Lower limit [g] ................ 0.05

Upper limit [g] ................ 0.15

Molar mass M ....................... 55.85


Titration stand .................... ST20A 1

Pump ........................... No

Pump ........................... No

Rinse .......................... Yes

Solvent...................... H2O

Volume [mL].................. 15.0

Conditioning ................... No


Stir

Speed [%] .......................... 50

Time [s] ........................... 15

EQP titration

Titrant/Sensor

Titrant ........................ 1/6 K2Cr2O7


Sensor ......................... DM140

Unit of meas. .................. mV

Predispensing ...................... to volume

Volume [mL] .................... 3.0

Wait time [s] .................. 10


dE(set) ........................ 4.0

dV(min) [mL] ................... 0.02

dV(max) [mL] ................... 0.15

Measure mode ....................... Equilibrium controlled

dE [mV] ........................ 1.0

dt [s] ......................... 1.0

t(min) [s] ..................... 6.0

t(max) [s] ..................... 25.0

Recognition

Threshold ...................... 200.0

Steepest jump only ............. No

Range .......................... No

Tendency ....................... Positive

Termination

at maximum volume [mL] ......... 20.0

at potential ................... No

at slope ....................... No

after number EQPs .............. Yes

n = ...................... 1

comb. termination criteria ..... No

Evaluation

Procedure ...................... Standard

Potential 1 ................... No

Potential 2 ................... No

Stop for reevaluation ......... No

Calculation

Formula ........................... R1=Q*C1/m

Constant ........................... C1=M/(10*z)

Decimal places ..................... 4

Result unit ........................ %

Result name ........................ iron content

Statistics ........................ Yes

Calculation

Formula ...........................

Constant ...........................

Decimal places ..................... 0

Result unit ........................

Result name ........................

Statistics ........................ No

Report


Results ............................ Yes

All results ........................ Yes

Raw results ........................ No

Table of measured values ........... Yes

Sample data ........................ No

E - V curve ........................ Yes

dE/dV – V curve .................... Yes

d2E/dV2 – V curve ................... No


E – t curve ........................ No

V – t curve ........................ No

dV/dt - t curve ................... No


001 Title



ID 10150

Title Iron in iron ores

Author METTLER TOLEDO

Date/Time 01.03.2010 15:00:00

Modified --

Modified by --

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Iron

Entry type Weight

Lower limit 0.05 g

Upper limit 0.15 g

Density 1.0 g/mL


Temperature 25.0°C


Type Manual stand


004 Stir

Speed 35%

Duration 15 s


Titrant

Titrant 1/6 K2Cr2O7


Sensor

Type mV

Sensor DMi140-SC

Unit mV



Stir

Speed 35%

Predispense

Mode Volume

Volume 3.0 mL

Wait time 10 s

Control

Control User


dE(set) 4.0

dV(min) 0.02 mL

dV(max) 0.15 mL


dE 1.0 mV

dt 1.0 s

t(min) 6.0 s

t(max) 25.0 s


Procedure Standard

Threshold 200 mV/mL

Tendency Positive

Ranges 0


Termination

At Vmax 20.0 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number EQPs 1


criteria No

006 Calculation R1

Result iron content

Result unit %

Formula R=Q*C/m

Constant C=M/(10*z)

M M[Iron]

z z[Iron]

Decimal places 4

Result limits No


Extra statistical

functions No

Send to buffer No

007 Record

Summary Yes

Results Per sample


Table of meas. Values Per sample

. . .

008 End of sample


METTLER TOLEDO Application M060-2010 Determination of Iron (Fe(II) ) and Sulphuric Acid (H2SO4)

Potentiometric determination of iron(II) by redox titration with potassium dichromate, K2Cr2O7, and of sulphuric acid by back titration of excess sodium hydroxide with hydrochloric acid. The potential is monitored by a combined platinum ring electrode (Fe), and a combined pH glass electrode (H2SO4).

Preparation and Procedures CAUTION: Use safety goggles and wear gloves.

Sample preparation: - 3-4 g FeSO4*7H2O (M = 278.02) is dissolved in a

500 mL volumetric flask with 150-200 mL 5% sulfuric acid solution.

- Shake the flask to dissolve iron sulfate, and fill up to the mark with 5% H2SO4 solution.

- Pipette 5 mL into a titration beaker.

Titration: Four methods are used to determine Fe(II)/H2SO4. The method sequence is the following:

1) 060 2) 060C 3) 060A 4) 060B

- Method 060 (Fe-determination): Fe(II)-Titration with K2Cr2O7. The pH value has to be between 2 and 3 to avoid oxidation of Fe(II). The result is multiplied by 2 (see “Chemistry”) and stored as auxil. value H2 to be used in method 060B.

- Method 060C (Back value determination): The exact amount of NaOH added to the sample is determined by titration with HCl. This value is stored as auxiliary value H3, and is used in method 060B.

- Method 060A (Sample preparation): Addition of 10 mL 0.1 mol/L NaOH to the Fe(II)-solution. H2SO4 and Fe(II) reacts with NaOH (see “Chemistry”). Since the reaction between Fe and OH- ions is slow, a -conditioning time of 1200 s has been defined in the method.

- Method 060B (Acid determination): A direct titration of H2SO4 is not possible since Fe(II) also reacts with NaOH. After addition of a known amount of NaOH, excess NaOH in the previously prepared samples (060A) is determined by back-titration with HCl. The difference between the sum (Fe + H2SO4) and Fe(II)-content (060) gives the H2SO4 content.

Remarks


- The electrode is rinsed after each sample with water.

Sample Fe(II)/H2SO4 aqueous solution, 5 mL c(H2SO4) = approx. 5% c(Fe) = approx. 6-7 g/L Fe(SO4)*7H2O

Compound Iron, Fe M = 55.85; z = 1 Sulfuric acid, H2SO4 M = 98.08; z = 2

Chemicals 5% sulfuric acid, H2SO4

Deionized water

Titrant Potassium dichromate, K2Cr2O7 c(1/6 K2Cr2O7) = 0.1 mol/L Hydrochloric acid, HCl, 0.1 mol/L Sodium hydroxide, NaOH, 0.1 mol/L

Standard For K2Cr2O7: (NH4)2Fe(SO4)2

For HCl: THAM (TRIS)

Indication Redox Pt-electrode, DMi140-SC

pH glass electrode, DGi111-SC

Chemistry Titration Fe(II): 2 Fe2+ + Cr2O7

2- + 14 H+ → 2 Fe3+ + 2 Cr3+ + 7 H2O

Reaction with NaOH: Fe2+ + 2 NaOH → Fe(OH)2 + 2 Na+ H2SO4 +2 NaOH→Na2SO4 + H2O

Titration excess NaOH: HCl + NaOH → NaCl + H2O

Calculation 060 : Content Fe(II), g/L • R = Q*C/m, C = M/z

060B: Content H2SO4 g/L • R = Q*C/m, C = M/z For DL7x : replace m with U (volume)

Waste disposal

Neutralize the sample before final disposal as special waste (Chromium).

Author, Version

Maria-José Schmid, MSG, Oct 1991 Revised March 2010 / C. De Caro


Instruments - DL70 Titrator - AT250 Balance This method can also be run with the T50/70/90 Titration Excellence, with the DL70ES/77

titrators, and with the DL5x and DL67 instruments (manual exchange of burettes).

Accessories - 3 x 10 mL DV1010 burette - 2 x additional DV090 burette drive - Sample Changer, i.e. Rondo 20 with pump - Titration beaker ME-101974

Results (Back-value, Fe-determination) 060C Back value measured Oct/18/1991 12:56 Oct/18/1991 12:30 Titrator P100 SW Version 2.0 User mjs RESULTS No Identification Volume Results 1/1 NaOH 12.0 mL 1.031 mmol Back value 1/2 NaOH 10.0 mL 1.030 mol/L mol/L 1/3 NaOH 10.0 mL 1.030 mol/L mol/L STATISTICS Number results R1 n = 3 Mean value x = 1.030 mmol Back value Standard deviation s = 0.0001 mmol Back value Rel. standard deviation srel = 0.006 % Outlier test: no outliers! AUXILIARY VALUE New value H3 = 1.030455 Back value NaOH ============================================================================================================= 060 Fe(II) determination measured Oct/01/1991 14:43 Oct/01/1991 11:53 Titrator P100 SW Version 2.0 User mjs RESULTS No Identification Volume Results 1/1 Fe+H2SO4 10.0 mL 0.0467 mol/L Fe(II) mol/L 6.487 g/L Fe(II) g/L 1/2 Fe+H2SO4 10.0 mL 0.0468 mol/L Fe(II) mol/L 6.504 g/L Fe(II) g/L 1/3 Fe+H2SO4 10.0 mL 0.0468 mol/L Fe(II) mol/L 6.508 g/L Fe(II) g/L 1/4 Fe+H2SO4 10.0 mL 0.0468 mol/L Fe(II) mol/L 6.511 g/L Fe(II) g/L 1/5 Fe+H2SO4 10.0 mL 0.0468 mol/L Fe(II) mol/L 6.501 g/L Fe(II) g/L 1/6 Fe+H2SO4 10.0 mL 0.0469 mol/L Fe(II) mol/L 6.517 g/L Fe(II) g/L 1/7 Fe+H2SO4 10.0 mL 0.0466 mol/L Fe(II) mol/L 6.483 g/L Fe(II) g/L STATISTICS Number results R1 n = 7 Mean value x = 0.0468 mol/L Fe(II) mol/L Standard deviation s = 0.00009 mol/L Fe(II) mol/L Rel. standard deviation srel = 0.193 % Outlier test: no outliers! STATISTICS Number results R2 n = 7 Mean value x = 6.502 g/L Fe(II) g/L Standard deviation s = 0.0126 g/L Fe(II) g/L Rel. standard deviation srel = 0.193 % Outlier test: no outliers!

AUXILIARY VALUE

New value H2 = 0.04677 Fe

Titration curve (Fe-determination)

Sample 1/7

Table of measured values (Fe-determination)

Sample 1/7



Comments

1. Both ferrous ion (Fe2+) and sulfuric acid (H2SO4) react with sodium hydroxide to Fe(OH)2, a solid precipitate, and to water and sodium sulfate. Thus, a direct titration of sulfuric acid is not possible when iron ions (Fe2+ and Fe3+ are present in the sample solution.

2. In addition, the reaction between ferrous ions, Fe2+, and hydroxide ions, OH-, is quite slow. Therefore, a direct titration of Fe2+ with sodium hydroxide is not suitable for titration analysis. For this reason, a back titration with a long waiting time after dispensing excess sodium hydroxide is the method of choice.

3. First, the back value of 10 mL 0.1 M sodium hydroxide is determined with hydrochloric acid (Method 060C). The result is stored as auxiliary value H3. Note that the pH glass electrode has to be adjusted using pH buffer solutions.

4. Subsequently, iron is selectively determined in the sample solution by redox titration with potassium dichromate as a titrant, K2Cr2O7 (Method 060). The result is multiplied by two (equivalence no. z = 2 for this reaction), it is expressed as FeSO4*7H2O, and stored as auxiliary value H2. 6 Fe2+ + Cr2O7

2- + 14 H+ → 6 Fe3+ + 2 Cr3+ + 7 H2O

The pH value of the sample solution (5 mL + 50 mL deionized water) has to be between 2 and 3.

5. Method 060A allows for sample preparation: 10 mL 0.1 M NaOH is added to the sample (5 mL) and a waiting time of 1200 s is defined to achieve complete reaction with iron ions.

6. Subsequently, this sample is analyzed by back-titration of excess NaOH with hydrochloric acid (Method 060B) to get the sulfuric acid content.

Results (H2SO4-determination)

060B Acid determination measured Oct/22/1991 12:11 Oct/22/1991 10:35 Titrator P100 SW Version 2.0 User mjs RESULTS No Identification Volume Results 1/1 Fe+H2SO4 5.0 mL 0.0969 mol/L Total sum 2.4563 g/L Acid content 1/2 Fe+H2SO4 5.0 mL 0.0970 mol/L Total sum 2.4588 g/L Acid content 1/3 Fe+H2SO4 5.0 mL 0.0974 mol/L Total sum 2.4817 g/L Acid content 1/4 Fe+H2SO4 5.0 mL 0.0971 mol/L Total sum 2.4654 g/L Acid content 1/5 Fe+H2SO4 5.0 mL 0.0979 mol/L Total sum 2.5059 g/L Acid content 1/6 Fe+H2SO4 5.0 mL 0.0973 mol/L Total sum 2.4767 g/L Acid content 1/7 Fe+H2SO4 5.0 mL 0.0973 mol/L Total sum 2.4753 g/L Acid content STATISTICS Number results R2 n = 7 Mean value x = 2.4743 g/L Acid content Standard deviation s = 0.01684 g/L Acid content Rel. standard deviation srel = 0.681 % Outlier test: no outliers!

Titration curve (H2SO4-determination)

Sample 1/7

Table of measured values (H2SO4-determination)

Sample 1/7



DL70 Titrator

Method 060C Back value

Version 18-Oct-1991 12:30

Title

Method ID .......................... 060C

Title .............................. Back value

Date/time .......................... 18-Oct-1991 12:30

Sample

Number samples ..................... 3

Titration stand .................... ST20

Entry type ......................... Fixed volume U

Volume [mL] .................... 10.0

ID ................................. NaOH

Molar mass M ....................... 40.0


Dispense

Titrant ........................... NaOH


Volume [mL] ........................ 10.0

Stir

Speed [%] .......................... 50

Time [s] ........................... 10

Titration

Titrant ............................ HCl


Sensor ............................. DG111-SC

Unit of meas. ...................... as installed


Predispensing 1 ................ mL

Volume [mL].................. 5.0

Predispensing 2 ................ To potential

Potential [mV,pH, …]......... 10.0

Titrant addition ............... DYN

dE(set)[mV].................. 8.0

Limits dV.................... Absolute

dV(min) [mL] .............. 0.02

dV(max) [mL] .............. 0.2

Measure mode ................... EQU

dE [mV]...................... 1.0

dt [s]....................... 1.0

t(min) [s]................... 2.0

t(max) [s]................... 20.0

Threshold ...................... 10.0



n = ......................... 1


Rinse

Auxiliary reagent .................. H2O

Volume [mL] ........................ 10.0

Calculation

Result name ....................... Back value

Formula ............................ R=Q

Constant ...........................

Result unit ........................ mmol

Decimal places ..................... 3

Statistics

Ri (i=index) ....................... R1


Rel. standard deviation srel ....... Yes

Auxiliary value

ID text ............................ Back value NaOH

Formula ............................ H3=x

Record


Results last sample ................ Yes

All results ........................ No

Conditioning

Interval ........................... 1

Time [s] ........................... 10

Method 060 Fe(II) determination


Title

Method ID...........................060

Title...............................Fe(II) determination

Date/time...........................01-Oct-1991 11:53

Sample

Number samples......................3

Titration stand.....................ST20

Entry type..........................Fixed volume U

Volume [mL] .....................10.0

ID..................................Fe+H2SO4

Molar mass M........................278.02

Equivalent number z.................1

Stir

Speed [%]...........................50

Time [s]............................10

Titration

Titrant.............................1/6 K2Cr2O7

Concentration [mol/L]...............0.1

Sensor..............................DM140-SC

Unit of meas........................mV

Titration mode......................EQP

Predispensing 1 .................mL

Volume [mL] ..................0.5

Titrant addition ................DYN

dE(set)[mV] ..................8.0

Limits dV ....................Relative

dV(min) [%dosVol] ..........0.5

dV(max) [%buVol] ...........5.0

Measure mode ....................EQU

dE [mV] ......................0.5

dt [s] .......................1.0

t(min) [s] ...................2.0

t(max) [s] ...................20.0

Threshold .......................200.0

EQP range .......................Yes

Limit A [mV,pH,…] ............550.0

Limit B [mV,pH,…] ............900.0

Maximum volume [mL] .............10.0

Termination at potential ........Yes

Potential [mV, pH, …] ........706.22

Termination after n EQPs ........Yes

n = .........................1

Evaluation procedure ............Standard

Steepest jump only ..............Yes

Calculation

Result name ........................Fe(II) mol/L

Formula.............................R=2*(Q*C/U)

Constant............................C=1

Result unit.........................mol/L

Decimal places......................4

Calculation

Result name ........................Fe(II) g/L

Formula.............................R2=Q*C2/U

Constant............................C2=M/z

Result unit.........................mol/L

Decimal places......................4

Rinse

Auxiliary reagent...................H2O

Volume [mL].........................10.0

Record

Output unit ........................Printer

Sample data.........................Yes

Raw results last sample.............Yes

Results last sample.................Yes

Statistics

Ri (i=index)........................R1

Standard deviation s................Yes

Rel. standard deviation srel........Yes

Outlier test........................Yes

Statistics

Ri (i=index)........................R2



Outlier test........................Yes

Auxiliary value

ID text.............................Fe

Formula.............................H2=x[1]

Record


Sample data.........................Yes



Table of measured values............Yes

E – V curve.........................Yes

dE/dV – V curve.....................Yes


Method 060A Sample preparation


Title

Method ID .......................... 060A

Title .............................. Sample preparation

Date/time .......................... 22-Oct-1991 10:30

Sample

Number samples ..................... 7

Titration stand .................... ST20

Entry type ......................... Fixed volume U

Volume [mL] .................... 5.0

ID ................................. Fe+H2SO4+NaOH

Molar mass M ....................... 0.0


Dispense

Titrant ........................... Sample


Volume [mL] ........................ 5.0

Dispense

Titrant ........................... NaOH


Volume [mL] ........................ 10.0

Stir

Speed [%] .......................... 60

Time [s] ........................... 60

Measure

Sensor ............................. DG111-SC

Unit of meas. ...................... as installed

dE [mV] ............................ 0.5

dt [s] ............................. 1.0

t(min) mode ........................ Fix

t(min) [s] ..................... 3.0

t(max) [s] ......................... 30.0

Calculation

Result name ....................... pH value

Formula ............................ R=E

Constant ...........................

Result unit ........................

Decimal places ..................... 1

Rinse

Auxiliary reagent .................. H2O

Volume [mL] ........................ 20.0

Conditioning

Interval ........................... 1

Time [s] ........................... 10

Statistics

Ri (i=index) ....................... R1


Rel. standard deviation srel ....... Yes

Conditioning

Interval ........................... 1

Time [s] ........................... 1200

Note:

After dispensing of NaOH solution the sample is left onto

the sample changer to allow for reaction during 1200 s.

The electrode is not left into the high alkaline solution to

avoid deterioration of the pH glass membrane with time.

Method 060B Acid determination


Title

Method ID...........................060B

Title...............................Acid determination

Date/time...........................22-Oct-1991 10:35

Sample

Number samples......................7

Titration stand.....................ST20

Entry type..........................Fixed volume U

Volume [mL] .....................5.0

ID..................................Fe+H2SO4

Molar mass M........................98.0

Equivalent number z.................2

Stir

Speed [%]...........................60

Time [s]............................10

Titration

Titrant.............................H2SO4

Concentration [mol/L]...............0.1

Sensor..............................DM111-SC

Unit of meas........................As installed

Titration mode......................EQP

Predispensing 1 .................mL

Volume [mL] ..................1.0

Titrant addition ................DYN

dE(set)[mV] ..................8.0

Limits dV ....................Absolute

dV(min) [mL] ...............0.02

dV(max) [mL] ...............0.2

Measure mode ....................EQU

dE [mV] ......................0.5

dt [s] .......................1.0

t(min) [s] ...................3.0

t(max) [s] ...................30.0

Threshold .......................3.0

Maximum volume [mL] .............10.0

Termination after n EQPs ........Yes

n = .........................1

Evaluation procedure ............Standard

Calculation

Result name ........................Total sum

Formula.............................R=(H3-Q)*C/U

Constant............................C=1

Result unit.........................mol/L

Decimal places......................4

Calculation

Result name ........................Acid content

Formula.............................R2=(R-H2)*C2

Constant............................C2=M/z

Result unit.........................g/L

Decimal places......................4

Rinse

Auxiliary reagent...................H2O

Volume [mL].........................10.0

Conditioning

Interval............................1

Time [s]............................10

Record




E – V curve.........................Yes

Statistics

Ri (i=index)........................R2



Outlier test........................Yes

Record


Short-form method...................Yes

Sample data.........................Yes


All results.........................Yes

Table of measured values............Yes

E – V curve.........................Yes

dE/dV – V curve.....................Yes

Conditioning

Interval............................1

Time [s]............................10



Back-value determination (H3):

001 Title



ID 060C

Title Back-value


Date/Time 01.03.2010 15:00:00

Modified --

Modified by --

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 HCl


Volume 10.0 mL

Density 1.0 g/mL


Temperature 25.0°C


Type Rondo/Tower A


004 Stir

Speed 35%

Duration 10 s

005 Titration (EQP)

Titrant

Titrant HCl


Sensor

Type pH

Sensor DGi111-SC

Unit pH



Stir

Speed 35%

Predispense

Mode Volume

Volume 5.0 mL

Wait time 10 s

Control

Control User


dE(set) 8.0

dV(min) 0.02 mL

dV(max) 0.2 mL


dE 0.5 mV

dt 1.0 s

t(min) 3.0 s

t(max) 30.0 s


Procedure Standard

Threshold 10 pH/mL

Tendency Negative

Ranges No


Termination

At Vmax 15.0 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number EQPs 1


criteria No

006 Rinse


Rinse cycles 1

Vol. per cycle 10.0 mL


007 Calculation R1

Result Back value

Result unit mL

Formula R=Q

Constant C=1

M M[None]

z z[None]

Decimal places 3

Result limits No


Extra statistical

functions No

Send to buffer No

008 Auxiliary value

Name H3

Formula Mean[R1]

009 Record

Summary No

Results Per sample


Table of meas. value Last titration function

Sample data No

Ressource data No

E – V Last titration function

dE/dV – V No

log dE/dV – V No

d2E/dV2 – V No

BETA – V No

E – t No

V – t No

dV/dt – t No

T – t No

E-V & dE/dV-V No

V-t & dV/dt-t No

Method No

Series data No

010 End of sample


Fe(II) determination (H2):

001 Title



ID 060

Title Fe(II) determination

. . .

002 Sample

Number of IDs 1

ID 1 Fe+H2SO4


Volume 10.0 mL

. . .


004 Stir

Speed 35%

Duration 10 s

005 Titration (EQP)

Titrant

Titrant 1/6 K2Cr2O7


Sensor

Type mV

Sensor DMi140-SC

Unit mV



Stir

Speed 35%

Predispense

Mode Volume

Volume 0.5 mL

Wait time 10 s

Control

Control User


dE(set) 8.0

dV(min) 0.02 mL

dV(max) 0.2 mL


dE 0.5 mV

dt 1.0 s

t(min) 2.0 s

t(max) 20.0 s


Procedure Standard

Threshold 200 mV/mL

Tendency Positive

Ranges No


Termination

At Vmax 10.0 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number EQPs 1


criteria No

007 Calculation R1

Result Fe concentration

Result unit mol/L

Formula R=2*(Q*C)/m

Constant C=1

M M[None]

z z[None]

Decimal places 4

. . .

008 Calculation R2

Result Fe concentration

Result unit g/L

Formula R2=Q*C2/m

Constant C2=M/z

M M[FeSO4*7H2O]

z z[FeSO4*7H2O]

Decimal places 3

. . .

009 Rinse


Rinse cycles 1



010 Auxiliary value

Name H2

Formula Mean[R1]

011 Record

Summary No

Results Per sample



Sample data No

Ressource data No


dE/dV – V No

log dE/dV – V No

d2E/dV2 – V No

BETA – V No

E – t No

V – t No

dV/dt – t No

T – t No

E-V & dE/dV-V No

V-t & dV/dt-t No

Method No

Series data No

012 End of sample

013 Record

Summary Yes

Results Yes

Raw results No

Ressource data No

Calibration curve No

Method No

Series data No

-------------------------------------------------------------

Sample preparation:

001 Title



ID 060A

Title Sample preparation


Date/Time 01.03.2010 15:00:00

Modified --

Modified by --

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Fe+H2SO4


Volume 5.0 mL

Density 1.0 g/mL


Temperature 25.0°C


Type Rondo/Tower A



Titrant Sample


Volume [mL] 5.0


Titrant NaOH


Volume [mL] 10.0

006 Stir

Speed 60%

Duration 60 s

007 Rinse


Rinse cycles 2


Position Rinse beaker

Drain Yes

Drain pump SP250

008 End of sample

009 Conditioning



Time 1200 s

Speed 25%


Acid determination:

001 Title



ID 060B

Title Acid determination


Date/Time 01.03.2010 15:00:00

Modified --

Modified by --

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Fe+H2SO4


Volume 5.0 mL

Density 1.0 g/mL


Temperature 25.0°C


Type Rondo/Tower A


004 Stir

Speed 35%

Duration 10 s

005 Titration (EQP)

Titrant

Titrant HCl


Sensor

Type pH

Sensor DGi111-SC

Unit pH



Stir

Speed 35%

Predispense

Mode Volume

Volume 1.0 mL

Wait time 10 s

Control

Control User


dE(set) 8.0

dV(min) 0.02 mL

dV(max) 0.2 mL


dE 0.5 mV

dt 1.0 s

t(min) 3.0 s

t(max) 30.0 s


Procedure Standard

Threshold 3.0 pH/mL

Tendency Negative

Ranges No


Termination

At Vmax 10.0 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number EQPs 1


criteria No

006 Calculation R1

Result Total sum

Result unit mol/L

Formula R=(H[H3]-Q)*C/m

Constant C=1

M M[H2SO4]

z z[H2SO4]

Decimal places 4

Result limits No


Extra statistical

functions No

Send to buffer No

007 Calculation R2

Result Acid content

Result unit g/L

Formula R2=(R1-H[H2])*C2

Constant C=M/z

M M[H2SO4]

z z[H2SO4]

Decimal places 4

Result limits No


Extra statistical

functions No

Send to buffer No

008 Rinse


Rinse cycles 1



009 Conditioning



Time 10 s

Speed 35%

010 Record

Summary No

Results Per sample



Sample data No

Ressource data No


dE/dV – V No

log dE/dV – V No

d2E/dV2 – V No

BETA – V No

E – t No

V – t No

dV/dt – t No

T – t No

E-V & dE/dV-V No

V-t & dV/dt-t No

Method No

Series data No

011 End of sample

012 Record

Summary Yes

Results Yes

Raw results No

Ressource data No

Calibration curve No

Method No

Series data No


Determination of Cr(III) by Back Titration in an Electroplating Bath Chromium (III) is determined by back titration of excess cerium(IV) sulphate solution with sodium nitrite.

Preparation and Procedures CAUTION: Work in a fume hood. Use gloves, lab coat and safety goggles. Principle:

Cr(III) is determined as Cr2O3 by back titration of excess cerium(IV) sulphate , Ce(SO4)2, solution.

Back value determination:

1.) Fill up a titration beaker with 50 mL with deionized water.

2.) 1:1 diluted HNO3 and Ce(SO4)2 solution are added with two dosing units.

3.) Ce(IV) is titrated with sodium nitrite. The back value is stored as B[Back] in mmol

Sample titration:

1.) Pipette 2 mL of chromium(III) bath to a beaker and fill up to 50 mL with deionized water.

2.) Sample preparation is automated by adding 1:1 diluted HNO3 and excess Ce(SO4)2 with two dosing units.

3.) Cr(III) is oxidized by excess Ce(IV) to Cr(VI) by the following reaction:

3 Ce4+ + Cr3+ → 3 Ce3+ + Cr6+

4.) Cr(III) is then determined by back titration of unreacted Ce(IV) using sodium nitrite (NaNO2):

2 Ce4+ + NO2- + H2O → 2 Ce3- + NO3

- + 2 H+

Remarks

- It is not necessary to heat the sample as mentioned in older applications.


- Rinse the electrode after each sample. If necessary, clean the metal ring of the electrode with a paper tissue at the end of each sample series.

Sample 2 mL aliquot of chromium(III) bath (approx. 8 g/L Cr(III))

Compound Cr(III) as Cr2O3 M = 151.99; z = 3

Chemicals - Deionized water - Nitric acid 1:1 - Cerium(IV) sulphate , Ce(SO4)2, c(Ce(SO4)2) = 0.1 mol/L

Titrant Sodium nitrite, NaNO2

c(1/2 NaNO2) = 0.2 mol/L

Standard Cerium(IV) sulphate , Ce(SO4)2

Indication DMi140-SC

Chemistry Cr(III) oxidation by Ce(IV): 3 Ce4+ + Cr3+ → 3 Ce3+ + Cr6+

Back titration of Ce4+: 2 Ce4+ + NO2

- + H2O → 2 Ce3- + NO3

- + 2 H+

Calculation Cr2O3 content in g/L: R=(B[Blank]-Q)*C/m; C = M/(z*2) (2 x Cr in Cr2O3) B[Back] = Back value in mmol Ce(SO4)2

Waste disposal

Heavy metal waste

Author, Version

Susanne Wahlen, MSG Anachem, April 2010


Instruments - T50/70/90 Titration Excellence - XS205 Balance - Rondo 20 Sample Changer

Accessories - 2 x 10 mL DV1010 burette - 1 x 5 mL DV1005 burette - 2 x additional dosing unit - Titration beakers ME-101974 - LabX titration pro


Method: 002 CHROM(III) 16.04.2010 17:07:54

Results



1/6 Cr2O3 16.04.2010 17:08:33 R1 = 2.018 mL Consumption

R2 = 7.314 (2) g/L Chromium(III)oxide


R2 = 7.265 g/L Chromium(III)oxide









Statistics: n = 5 R2 = 7.240 ± 0.018 g/L s = 0.0172 srel: 0.238% (2) excluded

Titration curve

Sample 2/6




Volume Increment Signal Change 1st deriv. Time mL mL mV mV mV/mL min:s -------------------------------------------------------------------------------------------- 0 1291.3 0 0.02 0.02 1290.7 -0.6 3 0.04 0.02 1290.2 -0.5 6 0.09 0.05 1289 -1.2 9 0.215 0.125 1286.2 -2.8 12 0.415 0.2 1281.4 -4.8 -23.91 15 0.615 0.2 1276.3 -5.1 -25.16 18 0.815 0.2 1271 -5.3 -27.73 21 1.015 0.2 1264.8 -6.2 -32.32 24 1.215 0.2 1257.7 -7.1 -40.05 28 1.415 0.2 1249 -8.7 -53.77 32 1.583 0.168 1239.7 -9.3 -75.21 36 1.696 0.113 1231.5 -8.2 -101.42 41 1.7815 0.0855 1223.4 -8.1 -136.73 46 1.8455 0.064 1215.2 -8.2 -188.09 51 1.8915 0.046 1207.4 -7.8 -280.21 58 1.9275 0.036 1199.4 -8 -475.65 65 1.955 0.0275 1190.8 -8.6 -755.81 73 1.975 0.02 1182.4 -8.4 -917.64 83 1.995 0.02 1170.1 -12.3 -1512.53 96 2.015 0.02 1144.1 -26 -1876.36 125 2.035 0.02 1086 -58.1 -1570.8 155 EQP1 2.036912 1077.8 -1935.31 2.055 0.02 999.7 -86.3 -1302.36 185 2.075 0.02 982.9 -16.8 -1232.25 200 2.124 0.049 965.5 -17.4 -829.18 211 2.177 0.053 954.6 -10.9 220 2.2445 0.0675 945.6 -9 226 2.3375 0.093 936.9 -8.7 233 2.4595 0.122 929.1 -7.8 239 2.6405 0.181 921 -8.1 244

Comments

--


Method 001 Title



ID 002

Title CHROM(III)


Date/Time 13.04.2010 14:45:58

Modified at 16.04.2010 17:07:54

Modified by admin

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Cr2O3


Volume [mL] 2.0

Density [g/mL] 1.0


Temperature 25.0


Type Rondo/Tower A


LidHandling No

004 Stir

Speed [%] 30

Duration [s] 2

Condition No


Titrant HNO3 (1 :1)

Concentration [mol/L] 1

Volume [mL] 5.0


Condition no


Titrant Ce(SO4)2


Volume [mL] 10.0


Condition no

007 Stir

Speed [%] 30

Duration [s] 300

Condition No


Titrant

Titrant ½ NaNO2


Sensor

Type mV

Sensor DMi140-SC

Unit mV



Stir

Speed [%] 30

Predispense

Mode None

Waiting time [s] 0

Control

Control User



dV (min) [mL] 0.02

dV (max) [mL] 0.2


dE [mV] 0.5

dt [s] 1.0

t(min) [s] 3.0

t(max) [s] 30


Procedure Standard

Threshold 200.0

Tendency Negative

Ranges 0


Termination

At Vmax 20

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQPs 1


criteria No



Condition

Condition No

009 Calculation R1

Result Consumption

Result unit mL

Formula R1=VEQ

Constant C= 1

M M[none]

z z[None]

Decimal places 3

Result limits No



Send to buffer No

Condition No

010 Calculation R2

Result Chromium(III)oxide

Result unit g/L

Formula R2=(B[Back]-Q)*C/m

Constant C= M/(z*2)

M M[Cr2O3]

z z[Cr2O3]

Decimal places 3

Result limits No



Send to buffer No

Condition No

011 Record

Summary No

Results Per sample


Table of meas. values Last titration function

Sample data No

Resource data No

E - V Last titration function

dE/dV - V Last titration function

log dE/dV - V No

d2E/dV2 - V No

BETA – V No

E - t No

V - t No

dV/dt - t No

T – t No



Method No

Series data No

Condition No

012 End of sample


Iodometric Titration of Cr(VI) in an Electroplating Bath Chromium is determined by redox titration of free iodine generated by reduction of Cr(VI) to Cr(III) with potassium iodide. Iodine is titrated with sodium thiosulfate and a combined platinum ring sensor.

Preparation and Procedures CAUTION:

Work in a fume hood. Use gloves, lab coat and safety goggles.

Sample titration:

- 2.5 mL chromium bath is diluted with deionized water to 250 mL. 5 mL of diluted aliquot corresponds to 0.05 mL of original sample. The latter value is defined as fixed sample volume.

- Sulphuric acid is automatically added by a dosing unit.

- The addition of potassium iodide KI by a pump leads to the reduction of Cr(VI) to Cr(III) according to the following reaction: 2 Cr6+ + 6I- = 2 Cr3+ + 3 I2 (z = 3)

- The amount of iodine formed is proportional to the Cr(VI) content.

- Generated I2 is then titrated with Na2S2O3: 2 S2O3

2- + I2 = S4O62- + 2 I-

Note: Stir moderately. Vigorous stirring causes loss of I2.

Remarks

- 1 mL Na2S2O3 corresponds to 3.33 mg CrO3.


- Rinse the electrode after each sample.

- If necessary, clean the metal ring of the sensor with a paper tissue at the end of each sample series.

Sample 5 mL aliquot from 1:100 diluted chromium(VI) bath

Compound Cr(VI) as CrO3 M = 99.99; z = 3

Chemicals - Deionized water - Sulphuric acid, 1:1 - Potassium iodide solution, KI 10% KI

Titrant Sodium thiosulphate, Na2S2O3

c(Na2S2O3)=0.1 mol/L

Standard Potassium iodate, KIO3


Chemistry Cr(VI) reduction to Cr(III): 2 Cr6+ + 6I- → 2 Cr3+ + 3 I2

Titration of iodine: 2 S2O3

2+ + I2 → S4O62- + 2 I-

Calculation CrO3 content in g/L: R=Q*C/m C=M/z

Waste disposal

Heavy metal waste

Author, Version

Susanne Wahlen, MSG Anachem, April 2010


Instruments - T50/70/90 Titration Excellence - XS205 Balance - Rondo 20 Sample Changer - SP250 Peristaltic pump ME-51108016

Accessories - 2 x 10 mL DV1010 burette - 1 x additional burette drive - Titration beakers ME-101974 - LabX titration pro


DL90 Fumehood

Method: 001 CHROMIUM(VI) 15.04.2010 17:06:09

Results



1/8 CrO3 15.04.2010 16:06:38 R1 = 4.381 mL Consumption

R2 = 292.065 g/L Chromium(VI)oxide








R2 = 302.104 (2) g/L Chromium(VI)oxide


R2 = 284.538 (2) g/L Chromium(VI)oxide




R2 = 290.468 % Chromium(VI)oxide

Statistics: n = 6 R2 = 292.719 ± 2.071 g/L s = 2.071 srel: 0.707% (2) excluded

Titration curve

Sample 2/8




Volume Increment Signal Change 1st deriv. Time mL mL mV mV mV/mL min:s -------------------------------------------------------------------------------------------- 0 NaN 355.9 NaN NaN 0 2 2 346.5 -9.4 NaN 6 2.05 0.05 346.4 -0.1 NaN 9 2.1 0.05 346.1 -0.3 NaN 12 2.15 0.05 345.8 -0.3 NaN 15 2.2 0.05 345.5 -0.3 -5.91 18 2.25 0.05 345.2 -0.3 -6.63 22 2.3 0.05 344.9 -0.3 -6.6 25 2.35 0.05 344.5 -0.4 -6.8 28 2.4 0.05 344.2 -0.3 -7 31 . . . . . . . . . . . . . . . . . . 3.1 0.05 338.3 -0.5 -10.28 73 4 0.05 323 -1.5 -30.8 128 4.05 0.05 321.4 -1.6 -34.63 131 4.1 0.05 319.5 -1.9 -39.51 134 4.15 0.05 317.2 -2.3 -40.39 137 4.2 0.05 314.5 -2.7 22.69 140 4.25 0.05 311.2 -3.3 -78.76 144 4.3 0.05 306.7 -4.5 -286.78 147 4.35 0.05 300.2 -6.5 -501.86 150 4.4 0.05 285.7 -14.5 -643.36 154 EQP1 4.431621 NaN 233.7 NaN -667.44 NaN 4.45 0.05 203.5 -82.2 -665.73 164 4.5 0.05 178.9 -24.6 -560.11 175 4.55 0.05 168.9 -10 -360.3 182 4.6 0.05 163 -5.9 -138.14 188 4.65 0.05 158.7 -4.3 2.37 192 4.7 0.05 155.9 -2.8 NaN 195 4.75 0.05 153.2 -2.7 NaN 198 4.8 0.05 150.8 -2.4 NaN 202 4.85 0.05 148.7 -2.1 NaN 204 4.9 0.05 146.8 -1.9 NaN 208

Comments

--


Method 001 Title



ID 001

Title Chromium(VI)


Date/Time 13.04.2010 10:32:13

Modified at 23.04.2010 12:23:15

Modified by admin

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 CrO3


Volume [mL] 0.05

Density [g/mL] 1.0


Temperature 25.0


Type Rondo/Tower A


Lid Handling No


Titrant H2SO4 1:1

Concentration 4.6

Volume [mL] 5.0


Condition no

005 Pump


Volume [mL] 40.0

Condition no

006 Pump

Auxiliary reagent KI

Volume [mL] 5.0

Condition No

007 Stir

Speed [%] 30

Duration [s] 90

Condition No


Titrant

Titrant Na2S2O3

Concentration [mol/L] 0.1 mol/L

Sensor

Type mV

Sensor DMi140-SC

Unit mV



Stir

Speed [%] 30

Predispense

Mode Volume

Volume [mL] 2.0

Waiting time [s] 0

Control

Control User


dV [mL] 0.05


dE [mV] 1.0

dt [s] 2.0

t(min) [s] 3.0

t(max) [s] 10.0


Procedure Standard

Threshold 200.0

Tendency Negative

Ranges 0


Termination

At Vmax 10

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQPs 1


criteria No

009 Calculation R1

Result Consumption

Result unit mL

Formula R1=VEQ

Constant C= 1

M M[none]

z z[None]

Decimal places 3

Result limits No



Send to buffer No

Condition No

010 Calculation R2

Result Chromium(VI)oxide

Result unit g/L

Formula R2=Q*C/m

Constant C= M/z

M M[Chromium(VI)oxide]

z z[Chromium(VI)oxide]

Decimal places 3

Result limits No



Send to buffer No

Condition No

011 Rinse


Rinse cycles 1

Vol. per cycle [mL] 10


Drain No

Condition No

012 End of sample

013 Park


Position Rinse beaker

Condition No

METTLER TOLEDO Application M461-2010 Determination of Manganese in Manganese Ores

Manganese is determined in slighlty acidic-neutral digested solutions by redox titration at 80°C with potassium permanganate KMnO4 as a titrant. The potential change is monitored by a combined platinum ring electrode.


Note: Check under “Comments and method” for the dissolution of manganese ores Sample preparation with pure MnO2:

- Approximately 0.5 g pure (> 99.9%) MnO2 is accurately weighed into a glass titration beaker.

- 20 mL deionized water HCl is added. - 30 mL 32% concentrated HCl is added. - The sample is heated (70-90°C) on a hot plate

under stirring to dissolve manganese dioxide. - After complete dissolution, the solution is cooled

to room temperature and is added into a 500 mL volumetric flask.

- Add deionized water to approx. 450 mL, gently shake the solution. If necessary, neutralize with Na2CO3 up to a neutral or slightly acidic solution.

- Fill up to the mark with deionized water.

Titration of Mn(II):

- 5 mL of the digested solution is added into a glass titration beaker.

- Add 60 mL deionized water. - Add 3 mL 10% ZnO suspension, and 5 mL

ZnSO4. - Start immediately the titration with KMnO4.

Remarks

- The content determination is based on a comparative titration of a standard solution. Thus, two titrations are performed: 1) Calibration titration with std. solution of known concentration, where a factor in mg/mL MnO2 is determined. 2) Content determination

- Perform both the calibration and sample titrations under exactly the same conditions.

- In this application, pure manganese dioxide has been used to prepare a digested ore sample.

- The parameters have been optimized for this application. It may be necessary to adapt the method to your sample.

Sample Manganese (IV) dioxide acid digested solution, MnO2 (approx. 0.5 g/500 mL) 5 mL

Compound Manganese, MnO2

M = 86.94; z = 2

Chemicals 32% hydrochloric acid, HCl

10% zinc oxide suspension, (ZnO in water)

ZnSO4 (10g/200 mL H2O)

Deionized water

Titrant Potassium permanganate, KMnO4 c(1/3 KMnO4) = 0.06 mol/L

Standard Sodium oxalate, Na2C2O4

(for 1/5 KMnO4), 0.025-0.040 g

Indication Combined redox Pt-electrode e.g. DMi140-SC

Chemistry Digestion and reduction to Mn(II): MnO2 + 4 HCl → MnCl2 + Cl2 + 2 H2O

Titration from Mn(II) to Mn(IV): 3 Mn2+ + 2 MnO4

- + 2 ZnO → 5 MnO2 + 2 Zn2+

Auxiliary reaction (masking of iron): 2 Fe3+ + 3 ZnO + 3 H2O → 2 Fe(OH)3 + 3 Zn2+

Calculation Content (%, as Mn): R1 = Q*C/m C = M/(10*z)

Waste disposal

Neutralize with sodium hydroxide before final disposal as metal solution.

Author, Version

Cosimo De Caro, MSG Anachem, April 2010



Instruments - T50/T70/T90 Titration Excellence - XS205 Balance - DH100 heating system - Rondo 20 sample changer

Accessories - 1 x 10 mL DV1010 burette - Glass titration beaker ME-101446 - LabX pro titration software

Calibration factor: Results

Sample Factor (mg/mL)

n srel (%)

ZnO H2O

mL mL Parameters INC TFIX mL s

Acid digested MnO2

solution, 5 mL (5.118 mg MnO

2)

2.863 ± 0.067

2.988 ± 0.052

2.866 ± 0.018

2.743 ± 0.025

2.950 ± 0.041

3.015 ± 0.024

2.980 ± 0.024

3.016 ± 0.063

6 2.345

6 1.726

6 0.626

6 0.924

6 1.381

6 0.802

6 0.812

6 1.095

3 60

3 60

3 60

3 60

3 60

3 60

3 60

20 40

0.1 30 80°C manual

0.1 15 80°C manual

0.1 30 80°C Rondo20

0.1 15 60°C Rondo20

0.1 30 80°C Rondo20, 0.7 mL predisp.

0.05 30 80°C Rondo20, 1 mL predisp.

0.1 15 80°C Rondo20 12 days later

0.1 45 80°C Rondo20

Acid digested MnO2

solution, 5 mL (5.368 mg MnO

2)

3.010 ± 0.030

3.041 ± 0.058

2.997 ± 0.048

6 0.999

4 1.905

4 1.600

10 50

10 60

5 60

0.1 30 80°C Rondo20

0.1 30 80°C Rondo20

0.02-1 mL, EQU: 0.5/3 mV/s, t=15-45 s

Standard solution MnSO

4 x H

2O in H

2O

5 mL

(9.576 mg MnSO4 x H2O)

7.242 ± 0.184

6.446 ± 0.144

5.709 ± 0.213

5.690 ± 0.142

5 2.545

6 2.242

5 3.724

5 2.504

5 60

5 60

3 60

3 60

0.1 30 80°C Rondo20 No acid

0.1 30 80°C Rondo20 1 mL 0.5 M HCl

0.1 30 80°C Rondo20 1 mL 0.5 M HCl 5 mL ZnSO4 (10g/200 mL H2O)

0.1 30 80°C Rondo20 1 mL 0.5 M HCl 5 mL ZnSO4 (10g/200 mL H2O) Conditioning: 0.5 M HCl

5.689 ± 0.087

5.994 ± 0.141

6.019 ± 0.039

3 1.535

3 2.357

3 0.654

5 50

1 60

3 60

0.1 5 80°C Rondo20 10 mL ZnSO4 (10g/200 mL H2O Conditioning: H2O

0.1 5 80°C Rondo20 3 mL ZnSO4 (10g/200 mL H2O) Conditioning: H2O 0.1 5 80°C Rondo20 5 mL ZnSO4 (10g/200 mL H2O) Conditioning: H2O

Note:

- When using less than 3 mL ZnO suspension no titration was possible. With more than 3 mL, the result is more or less constant.

- A variation of several parameters such as the titration method parameters (increments, titration modes, signal acquisition,..) and sample preparation (use of Mg standard solution, pH neutral sample solution,…) did not show any significant influence on the results.

Calibration factor: Titration curve

Sample 1/6 - 8.4.2010 09:02 CDCMnOMnO2RONDO

Calibration factor: Table of measured values

Volume Increment Signal Change 1st deriv. Time Temperature mL mL mV mV mV/mL s °C -------------------------------------------------------------------------------------- 0.0000 NaN 393.7 NaN NaN 0 25.0 0.1000 0.1000 407.0 13.3 NaN 30 25.0 0.2000 0.1000 415.5 8.5 NaN 60 25.0 0.3000 0.1000 418.6 3.1 NaN 90 25.0 0.4000 0.1000 425.4 6.8 NaN 121 25.0 0.5000 0.1000 430.0 4.6 44.67 151 25.0 0.6000 0.1000 434.2 4.2 51.44 181 25.0 0.7000 0.1000 440.1 5.9 55.84 211 25.0 0.8000 0.1000 448.4 8.3 54.58 241 25.0 0.9000 0.1000 447.6 -0.8 57.50 272 25.0 1.0000 0.1000 459.9 12.3 52.96 302 25.0 1.1000 0.1000 462.2 2.3 46.86 332 25.0 1.2000 0.1000 467.1 4.9 39.99 362 25.0 1.3000 0.1000 473.4 6.3 29.44 392 25.0 1.4000 0.1000 476.0 2.6 69.54 422 25.0 1.5000 0.1000 484.9 8.9 165.42 452 25.0 1.6000 0.1000 497.0 12.1 275.11 483 25.0 1.7000 0.1000 523.3 26.3 350.54 513 25.0 EQP1 1.764479 NaN 562.9 NaN 365.64 NaN NaN 1.8000 0.1000 584.7 61.4 363.09 543 25.0 1.9000 0.1000 620.4 35.7 303.67 573 25.0 2.0000 0.1000 644.0 23.6 191.62 603 25.0 2.1000 0.1000 644.3 0.3 57.39 634 25.0 2.2000 0.1000 644.7 0.4 -50.26 664 25.0 2.3000 0.1000 640.6 -4.1 NaN 694 25.0 2.4000 0.1000 630.8 -9.8 NaN 724 25.0 2.5000 0.1000 619.4 -11.4 NaN 754 25.0 2.6000 0.1000 609.0 -10.4 NaN 784 25.0 2.7000 0.1000 605.8 -3.2 NaN 815 25.0 Sample 1/6 - 8.4.2010 09:02 CDCMnOMnO2RONDO



Sample determination: Results

Calibration factor:

Sample Factor (mg/mL)

n srel (%)

ZnO H2O


Acid digested MnO

2 solution,

5 mL (5.118 mg MnO

2)

2.863 ± 0.067

2.866 ± 0.018

2.950 ± 0.041

6 2.345

6 0.626

6 1.381

3 60

3 60

3 60

0.1 30 80°C manual

0.1 30 80°C Rondo20

0.1 30 80°C Rondo20, 0.7 mL predisp.

Average calibration factor

2.893 ± 0.049 3 1.707

Sample determination:

Sample Consumption (mL) Recovery rate (%)

ZnO H2O


Acid digested MnO

2 solution,

5 mL (5.118 mg MnO

2)

Sample Series (9) 24.03.2010 12:25

1/6

2/6

3/6

4/6

5/6

6/6

1.774

1.774

1.781

1.799

1.798

1.787

100.28

100.28

100.67

101.69

101.63

101.01

3 60

3 60

3 60

3 60

3 60

3 60

0.1 30 80°C Rondo20

0.1 30 80°C Rondo20

0.1 30 80°C Rondo20

0.1 30 80°C Rondo20

0.1 30 80°C Rondo20

0.1 30 80°C Rondo20

Average (%) 100.93

Std. deviation (%)

0.630

Rel. Std. dev. (%)

0.624

Sample Series (8) 25.03.2010 09:19

1/6

2/6

3/6

4/6

5/6

6/6

1.706

1.731

1.778

1.723

1.741

1.733

96.43

97.85

100.50

97.39

98.41

97.96

3 60

3 60

3 60

3 60

3 60

3 60

0.1 30 80°C Rondo20, 0.7 mL predispensing






Average (%) 98.09

Std. deviation (%)

1.359

Rel. Std. dev. (%)

1.385

Sample determination: Titration curve

Sample 6/6 – 24.3.2010 12:25 CDCMnOMnO2RONDO2 (9)

Sample determination: Table of measured values

Volume Increment Signal Change 1st deriv. Time Temperature mL mL mV mV mV/mL s °C -------------------------------------------------------------------------------------- 0.0000 NaN 430.6 NaN NaN 0 25.0 0.1000 0.1000 429.7 -0.9 NaN 30 25.0 0.2000 0.1000 428.5 -1.2 NaN 60 25.0 0.3000 0.1000 430.5 2.0 NaN 91 25.0 0.4000 0.1000 431.2 0.7 NaN 121 25.0 0.5000 0.1000 431.4 0.2 7.83 151 25.0 0.6000 0.1000 430.7 -0.7 6.44 181 25.0 0.7000 0.1000 433.3 2.6 6.78 211 25.0 0.8000 0.1000 433.7 0.4 10.33 242 25.0 0.9000 0.1000 434.4 0.7 12.53 272 25.0 1.0000 0.1000 435.2 0.8 14.11 302 25.0 1.1000 0.1000 438.2 3.0 17.03 332 25.0 1.2000 0.1000 439.5 1.3 21.44 362 25.0 1.3000 0.1000 441.6 2.1 -21.34 392 25.0 1.4000 0.1000 445.0 3.4 -0.37 423 25.0 1.5000 0.1000 449.4 4.4 140.21 453 25.0 1.60000 0.1000 453.6 4.2 298.77 483 25.0 1.7000 0.1000 462.4 8.8 410.61 513 25.0 EQP1 1.787293 NaN 542.9 NaN 445.71 NaN NaN 1.8000 0.1000 554.6 92.2 445.67 543 25.0 1.9000 0.1000 626.3 71.7 393.96 574 25.0 2.0000 0.1000 626.4 0.1 268.65 604 25.0 2.1000 0.1000 632.8 6.4 112.76 634 25.0 2.2000 0.1000 640.2 7.4 -0.71 664 25.0 2.3000 0.1000 644.8 4.6 NaN 694 25.0 2.4000 0.1000 647.9 3.1 NaN 724 25.0 2.5000 0.1000 652.2 4.3 NaN 754 25.0 2.6000 0.1000 656.2 4.0 NaN 785 25.0 2.7000 0.1000 657.0 0.8 NaN 815 25.0 Sample 6/6 – 24.3.2010 12:25 CDCMnOMnO2RONDO2 (9)




• A direct titration always leads to lower content values (see below). Thus, the determination of manganese in ores is based on a comparative titration between a standard and the sample solution:

1. First, the titrant consumption for the titration of a standard solution of known concentration is determined. The result is stored as auxiliary value H[CalibFactorMn] in mg/mL MnO2. A known amount of MnO2 is digested in acid in order to get Mn(II)-ions into solution.

2. Subsequently, the titrant consumption for the sample is determined. The result is obtained by multiplying the calibration factor H[CalibFactorMn] with the titrant consumption.

• Only a slight excess of ZnO suspension is needed.

• It is very important that both titrations are performed exactly in the same way i.e. stirring speed, T,…

Manganese ore dissolution: In this application, the titration has been performed using acid digested solution of MnO. The application can be also run with manganese ores. A customer procedure for the dissolution of manganese ores is as it follows: - Weigh 0.1 g of dried sample in a platinum crucible and 2 g of Na2CO3; - Leave the crucible in a muffle oven at 700°C, raise the temperature until 950°C and leave it during 20min; - Remove the sample and wait until the sample is cooled down; - Dissolve the molten mass in a 250 mL beaker with 50mL 1:1 HCl on a hot plate at 100°C and shake; - Transfer to an 1000mL Erlenmeyer flask and leave on a hot plate at 250°C until the volume is reduced to 10mL.

Subsequently, leave it on the hot plate at 100°C until dryness; - Add 700 mL of hot water and leave to boil on the hot plate; - Add sufficient 10% (w/w) ZnO suspension until the solution turns white, and titrate in the heat with KMnO4 to EQP.

Chemical reaction: Mn(II) is titrated by permanganate titration at 80°C in a neutral or slightly acidic solution leading to the formation of Mn(IV) according to the reaction

3 Mn2+ + 2 MnO4- + 2 ZnO → 5 MnO2 + 2 Zn2+

In iron-manganese ores or in manganese alloys, iron needs to be masked since it affects the manganese determination. This is done by precipitating iron with zinc oxide.

2 Fe3+ + 3 ZnO + 3 H2O → 2 Fe(OH)3 + 3 Zn2+

A detailed analysis of the chemical reaction shows that Mn(IV) is precipitated as manganese oxyde hydrate, MnO2·H2O, a dark brown compound which is clearly visible in the solution:

2 MnO4- + 3 Mn2+ + 7 H2O → 5 MnO2·H2O + 4 H+

The formation of manganese oxyde hydrate leads to adsorption of bivalent ions such as Mn(II) and Zn(II). If unreacted Mn(II) is adsorbed, then mixed Mn(II)-Mn(IV) oxide hydrate with formula Mn(HMnO3)2 is precipitated. As a consequence, the titrant consumption is smaller than expected. To avoid it, ZnO suspension and also ZnSO4 solution are added. Thus, the addition of excess ZnO suspension is needed to first neutralize the resulting acid protons, to mask iron, and also to suppress adsorption and co-precipitation of unreacted Mn(II).

Nevertheless, the oxidation of Mn(II) to Mn(IV) seems still not to be complete when reaching the equivalence point. Thus, it is necessary to heat again to 80°C the titrated solution, then continues the analysis until the equivalence point is reached again. For this reason, a comparative titration is more suitable for routine analysis.

Literature: [1] www.chemguide.co.uk/inorganic/transition/manganese.html, and www.titrations.info/permanganate-titration . [2] Jander Jahr, “Massanalyse”, ed. by Gerhard Schulze and Jürgen Simon, 14th Edition, de Gruyter, 1986 (German). [2] Othmar G. Koch, „Analytische Chemie des mangans“, Springer-Verlag, 1985 (German). [4] József Mika, „Metallurgische Analysen”, Akademische Verlagsgesellschaft, Geest & Portig K.-G., Leipzig 1964

(German).

http://www.chemguide.co.uk/inorganic/transition/manganese.html

http://www.titrations.info/permanganate-titration


Calibration factor

001 Title



ID m461Calib

Title Calibration factor Mn


Date/Time 01.06.2010 15:00:00

Modified --

Modified by --

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 MnO2 Standard solution


Volume 5.0 mL

Density 1.0 g/mL


Temperature 25.0°C


Type Rondo/Tower A


004 Stir

Speed 50%

Duration 60 s

005 Auxiliary instrument

Control type Out TTL (Single pin)

Name DH100 TTL on

Mode Fixed time

Time 2 s

006 Measure (normal) [1]

Sensor

Type Temperature

Sensor DT1000

Unit °C

Stir

Speed 50%


Acquisition Set value

Mode T>set value

Set value 80°C

t(max) 300

Mean value No


Titrant

Titrant 1/3 KMnO4


Sensor

Type mV

Sensor DMi140-SC

Unit mV



Stir

Speed 50%

Predispense

Mode None

Wait time 0 s

Control

Control User


dV 0.1 mL

Meas. val. acquisition Fixed time

dt 30 s


Procedure Standard

Threshold 150 mV/mL

Tendency Positive

Ranges 0


Termination

At Vmax 10.0 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number EQPs 1


criteria No



Name DH100 TTL off

Mode Fixed time

Time 2 s

009 Calculation R1

Result Consumption

Result unit mL

Formula R=VEQ

Constant C=1

M M[None]

z z[None]

Decimal places 3

Result limits No


Extra statistical

functions No

Send to buffer No

010 Calculation R2

Result Calibration factor

Result unit mg/mL

Formula R2=(C*m)/VEQ

Constant C=H[MnO2Std]

M M[None]

z z[None]

Decimal places 3

Result limits No


Extra statistical

functions No

Send to buffer No

011 Rinse



Rinse cycles 1

Vol.per cycle 20


Drain No

012 Conditioning


Type Fix

Interval 1


Time 60 s

Speed 70%

013 End of sample

014 Auxiliary value

Name CalibFactor

Formula H= Mean[R2]

--------------------------------------------------------------

Calculation R2: C: H[MnO2Std] Concentration of the digested MnO2 standard solution e.g. 0.5118 g MnO2 in 500 mL H = 0.5118/500 = 0.0010236 g/mL = 1.0236 mg/mL


Sample titration

001 Title



ID m461sample

Title Sample titration Mn


Date/Time 01.06.2010 15:00:00

Modified --

Modified by --

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Digested ore solution


Volume 5.0 mL

Density 1.0 g/mL


Temperature 25.0°C


Type Rondo/Tower A


004 Stir

Speed 50%

Duration 60 s



Name DH100 TTL on

Mode Fixed time

Time 2 s

006 Measure (normal) [1]

Sensor

Type Temperature

Sensor DT1000

Unit °C

Stir

Speed 50%


Acquisition Set value

Mode T>set value

Set value 80°C

t(max) 300

Mean value No


Titrant

Titrant 1/3 KMnO4


Sensor

Type mV

Sensor DMi140-SC

Unit mV



Stir

Speed 50%

Predispense

Mode None

Wait time 0 s

Control

Control User


dV 0.1 mL

Meas. val. acquisition Fixed time

dt 30 s


Procedure Standard

Threshold 150 mV/mL

Tendency Positive

Ranges 0


Termination

At Vmax 10.0 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number EQPs 1


criteria No



Name DH100 TTL off

Mode Fixed time

Time 2 s

009 Calculation R1

Result Consumption

Result unit mL

Formula R=VEQ

Constant C=1

M M[None]

z z[None]

Decimal places 3

Result limits No


Extra statistical

functions No

Send to buffer No

010 Calculation R2

Result MnO2 Amount

Result unit mg

Formula R2=H[CalibFactor]*VEQ

Constant C=1

M M[None]

z z[None]

Decimal places 3

Result limits No


Extra statistical

functions No

Send to buffer No

011 Calculation R3

Result MnO2 Content

Result unit %

Formula R3=((R2/1000)/H[Ore])*100

Constant C=H[Ore]

M M[MnO2]

z z[MnO2]

Decimal places 3

Result limits No


Extra statistical

functions No

Send to buffer No

012 Rinse



Rinse cycles 1

Vol.per cycle 20


Drain No

013 Conditioning


Type Fix

Interval 1


Time 60 s

Speed 70%

014 End of sample

METTLER TOLEDO Application M466A-2010

Aluminum Content in Aluminum Ore (Bauxite) – Bayer Liquor Determination of free alkali and aluminum content in aluminum ore (Bauxite) by potentiometric titration with hydrochloric acid according to the Bayer procedure. The titration is monitored with a pH glass combined sensor.

Preparation and Procedures

CAUTION: Work in a fume hood and wear gloves and safety goggles.

- Weight in about 30 gr into a 600 mL Erlenmeyer flask.

- Add 350 mL 7 mol/L NaOH and cover it with a watch glass.

- Heat the sample on a heating plate set at 200°C, and keep it boiling while continuously stirring for at least 4 hours.

- The alumina is first converted into aluminum hydroxide, Al(OH)3, and further to [Al(OH)4]-

which is dissolved in the hydroxide solution.

- Some components are not dissolved; these are mainly insoluble iron hydroxide compounds.

- Let the solution cool down; prepare a 500 ml volumetric flask with a glass funnel and a paper filter to avoid the solid impurities.

- Filter the cooled solution into the 500 mL volumetric flask.

- Wash the paper filter with 100 mL 7 M NaOH.

- Mix well and fill up to the mark with deionized water, and mix again. Note: Temperature can increase again; thus, filling with water may be necessary again.

- 5 mL sample solution is added to a titration beaker together with 35 mL deion. water.

Remarks

- Rinsing and conditioning of the pH sensor is crucial to achieve accurate and precise results. In fact, the pH sensor is titrating in a strong alkaline solution (pH > 12).

- The parameters have been optimized for this specific sample solution. It may be necessary to adapt the method to your sample.

- The %-content Al2O3 is calculated from the mg/g-content Al(OH)3 (see R4) by multiplying it with a conversion factor from the ratio between M(Al2O3) and M(Al(OH3)) (see R5).

Sample 5 mL alkaline digestion solution from original aluminum ore (Bayer Liquor, 30.23 g/500 mL)

Compound Aluminum trihydroxide, Al(OH)3 M = 78.00 g/mol, z = 3 Sodium hydroxide, NaOH M = 40.00 g/mol, z = 1

Chemicals 25% Na-gluconate, NaC6H11O7 30% Potassium fluoride, KF Deionized water (see Preparation and

Titrant Hydrochloric acid, HCl c(HCl) = 1 mol/L c(HCl) = 0.1 mol/L

Standard Tris(hydroxymethyl)-aminomethane, THAM

Indication DGi115-SC

Chemistry OH- + H3O+ → 2 H2O see “Comments” for more detailed information

Calculation Free Caustic NaOH (g/L): R1 = (Q-Q2)*C/m ; C=M/z Free Carbonate CaCO3 (g/L): R2 = Q2*C/m ; C=M/z Aluminum hydroxide Al(OH)3 (g/L): R3 = (Q[2]+QEX)*C/m ; C = M/z, M = 78.00 , z = 3 (see “Comments”)

Waste

disposal

After neutralization dispose the sample solution as heavy metals.

Author,

Version

Cosimo De Caro MSG Anachem, July 2010

METTLER TOLEDO Page 1 of 7 Titration Application M466A-2010


Instruments - T70 / T90 Titration Excellence - Analytical Balance, e.g. XP205 - Precision Balance, e.g. MS6002S - Rondo 20 sample changer

Accessories - 3 additional dosing units - 2 x 10 mL DV1010 burette, 2 x 20 ml DV1020 burette - PP Titration beakers ME-101974

- LabX pro titration software

Results

No. Comment / ID Start time Sample size and results

1/6 +25 mL H2O / 30.23g/500mL + 10 mL 3g/60mLNa2CO3 -- 22.07.2010 08:30:39 R1 = 279.72 g/L Free Caustic NaOH R2 = 83.60 g/L Free Carbonate CaCO3 R3 = 18.42 g/L Content Al(OH)3 (g/L) R4 = 304.71 mg/g Content Al(OH)3 (mg/g) R5 = 39.83 % Content Al2O3 (%) 2/6 +25 mL H2O / 30.23g/500mL + 10 mL 3g/60mLNa2CO3 -- 22.07.2010 08:47:48 R1 = 276.73 g/L Free Caustic NaOH R2 = 85.45 g/L Free Carbonate CaCO3 R3 = 18.19 g/L Content Al(OH)3 (g/L) R4 = 300.89 mg/g Content Al(OH)3 (mg/g) R5 = 39.33 % Content Al2O3 (%) 3/6 +25 mL H2O / 30.23g/500mL + 10 mL 3g/60mLNa2CO3 -- 22.07.2010 09:04:36 R1 = 275.96 g/L Free Caustic NaOH R2 = 82.50 g/L Free Carbonate CaCO3 R3 = 18.10 g/L Content Al(OH)3 (g/L) R4 = 299.43 mg/g Content Al(OH)3 (mg/g) R5 = 39.14 % Content Al2O3 (%) 4/6 +25 mKL HO / 30.23g/500mL + 10 mL 3g/60mLNa2CO3 -- 22.07.2010 09:21:20 R1 = 275.76 g/L Free Caustic NaOH R2 = 85.72 g/L Free Carbonate CaCO3 R3 = 18.18 g/L Content Al(OH)3 (g/L) R4 = 300.74 mg/g Content Al(OH)3 (mg/g) R5 = 39.31 % Content Al2O3 (%) 5/6 +25 mL H2O / 30.23g/500mL + 10 mL 3g/60mLNa2CO3 -- 22.07.2010 09:38:06 R1 = 274.60 g/L Free Caustic NaOH R2 = 84.16 g/L Free Carbonate CaCO3 R3 = 18.21 g/L Content Al(OH)3 (g/L) R4 = 301.19 mg/g Content Al(OH)3 (mg/g) R5 = 39.37 % Content Al2O3 (%) 6/6 +25 mL H2O / 30.23g/500mL + 10 mL 3g/60mLNa2CO3 -- 22.07.2010 09:54:50 R1 = 276.91 g/L Free Caustic NaOH R2 = 85.52 g/L Free Carbonate CaCO3 R3 = 18.38 g/L Content Al(OH)3 (g/L) R4 = 303.94 mg/g Content Al(OH)3 (mg/g) R5 = 39.73 % Content Al2O3 (%) Statistics Rx Name n Mean value Unit s srel [%] R1 Free Caustic NaOH 6 276.61 g/L 1.729829 0.625 R2 Free Carbonate CaCO3 6 84.49 g/L 1.292786 1.530 R3 Content Al(OH)3 (g/L) 6 18.25 g/L 0.125167 0.686 R4 Content Al(OH)3 (mg/g) 6 301.82 mg/g 2.048743 0.679 R5 Content Al2O3 (%) 6 39.45 % 0.267806 0.679

Titration curve (1st Titration: NaOH and carbonate)

Sample 1/6 22.07.2010 08:30

Table of measured values (1st Titration: NaOH and carbonate) Volume Increment Signal Change 1st derive. Time Temperature mL mL pH pH pH/mL s °C ------------------------------------------------------------------------------------------------------------------------------------------------------------------------ 0.000 NaN 13.542 NaN NaN 0 25.0 17.143 17.143 13.295 -0.247 NaN 20 25.0 25.714 8.571 13.024 -0.271 NaN 57 25.0 30.000 4.286 12.842 -0.182 NaN 63 25.0 30.200 0.200 12.794 -0.048 NaN 82 25.0 30.400 0.200 12.781 -0.013 -0.06 85 25.0

... ... ... ... ... ... ... 39.011 0.088 11.242 -0.070 -0.86 220 25.0 39.151 0.140 11.114 -0.128 -0.92 224 25.0 EQP1 39.219895 11.049 NaN -0.93 NaN NaN 39.248 0.097 11.023 -0.091 -0.93 227 25.0 39.354 0.106 10.922 -0.101 -0.88 230 25.0 39.460 0.106 10.826 -0.096 -0.84 234 25.0 39.579 0.119 10.735 -0.091 -0.79 236 25.0 39.736 0.157 10.618 -0.117 -0.72 240 25.0 39.876 0.140 10.526 -0.092 -0.66 243 25.0 40.056 0.180 10.404 -0.122 -0.60 272 25.0 40.202 0.146 10.321 -0.083 -0.54 275 25.0 40.402 0.200 10.219 -0.102 -0.48 278 25.0 40.602 0.200 10.044 -0.081 -0.41 284 25.0 41.002 0.200 9.968 -0.076 -0.41 287 25.0 41.202 0.200 9.879 -0.089 -0.41 290 25.0 41.402 0.200 9.797 -0.082 -0.41 293 25.0 41.602 0.200 9.712 -0.085 -0.42 296 25.0 41.802 0.200 9.627 -0.085 -0.43 299 25.0 42.002 0.200 9.542 -0.085 -0.45 302 25.0 42.202 0.200 9.442 -0.100 -0.50 305 25.0 42.402 0.200 9.338 -0.104 -0.57 309 25.0 42.595 0.193 9.228 -0.110 -0.67 312 25.0 42.758 0.163 9.109 -0.119 -0.81 315 25.0 42.868 0.110 9.015 -0.094 -0.93 318 25.0 42.971 0.103 8.918 -0.097 -1.11 321 25.0 43.069 0.098 8.811 -0.107 -1.35 324 25.0 43.150 0.081 8.701 -0.110 -1.64 327 25.0 43.211 0.061 8.600 -0.101 -1.94 330 25.0 43.261 0.050 8.493 -0.107 -2.29 333 25.0 43.298 0.037 8.401 -0.092 -2.60 336 25.0 43.334 0.036 8.302 -0.099 -2.93 339 25.0 43.368 0.034 8.191 -0.111 -3.27 342 25.0 43.394 0.026 8.111 -0.080 -3.47 345 25.0 EQP2 43.404282 NaN 8.071 NaN -3.47 NaN NaN 43.429 0.035 7.975 -0.136 -3.43 348 25.0 43.450 0.021 7.895 -0.080 -3.22 352 25.0 43.477 0.027 7.813 -0.082 -2.91 356 25.0 43.520 0.043 7.691 -0.122 -2.54 360 25.0 43.559 0.039 7.606 -0.085 -2.25 365 25.0 43.620 0.061 7.484 -0.122 NaN 371 25.0 43.676 0.056 7.395 -0.089 NaN 376 25.0 43.756 0.080 7.284 -0.111 NaN 381 25.0 43.842 0.086 7.187 -0.097 NaN 387 25.0 43.952 0.110 7.085 -0.102 NaN 393 25.0


Titration curve (2nd Titration: Aluminum)

Sample 1/6 22.07.2010 08:30

Table of measured values (2nd Titration: Aluminum) Volume Increment Signal Change 1st deriv. Time Temperature mL mL mV mV mV/mL s oC --------------------------------------------------------------------------------------------------------------------------------------------------------------------- 0.000 NaN -191.9 NaN NaN 0 25.0 0.005 0.005 -191.7 0.2 NaN 3 25.0 0.010 0.005 -191.6 0.1 NaN 6 25.0 0.022 0.012 -191.3 0.3 NaN 9 25.0 0.052 0.030 -190.4 0.9 NaN 12 25.0 0.127 0.075 -188.4 2.0 26.57 15 25.0 0.315 0.188 -183.7 4.7 24.46 19 25.0 0.515 0.200 -178.8 4.9 23.88 23 25.0 0.715 0.200 -174.2 4.6 23.24 26 25.0 0.915 0.200 -169.8 4.4 23.22 31 25.0 1.115 0.200 -164.8 5.0 23.99 35 25.0 1.315 0.200 -159.6 5.2 24.70 38 25.0 1.515 0.200 -155.2 4.4 26.05 42 25.0 1.715 0.200 -149.3 5.9 27.88 46 25.0 1.915 0.200 -143.2 6.1 30.89 50 25.0 2.115 0.200 -137.1 6.1 36.57 54 25.0 2.315 0.200 -128.8 8.3 45.60 58 25.0 2.503 0.188 -119.9 8.9 59.88 61 25.0 2.650 0.147 -110.6 9.3 78.62 65 25.0 2.746 0.096 -102.7 7.9 96.22 68 25.0 2.819 0.073 -96.1 6.6 111.74 72 25.0 2.900 0.081 -85.7 10.4 130.48 76 25.0 2.944 0.044 -80.1 5.6 144.01 79 25.0 EQP1 3.002191 NaN -70.0 NaN 158.53 NaN NaN 3.006 0.062 -69.3 10.8 158.46 83 25.0 3.040 0.034 -62.2 7.1 154.14 86 25.0 3.072 0.032 -57.5 4.7 139.57 90 25.0 3.150 0.078 -46.9 10.6 121.06 95 25.0 3.213 0.063 -40.0 6.9 107.18 100 25.0 3.305 0.092 -31.7 8.3 NaN 106 25.0 3.413 0.108 -23.8 7.9 NaN 111 25.0 3.546 0.133 -14.9 8.9 NaN 116 25.0 3.679 0.133 -7.8 7.1 NaN 121 25.0 3.862 0.183 0.7 8.5 NaN 126 25.0


Comments

Principle:

• Bauxite contains approximately 30 – 54% alumina (Al2O3). The rest mainly consists of silica, iron oxides, and titanium dioxide.

• During the Bayer process bauxite is digested by washing with a hot solution of sodium hydroxide, NaOH, at 175°C. The alumina is first converted into aluminum hydroxide, Al(OH)3, which subsequently dissolves in the hydroxide solution according to the chemical equation:

Al2O3 + 2 OH- + 3 H2O → 2 [Al(OH)4]- The resulting, strong alkaline solution is called “Bayer liquor”.

Left: Bauxite powder Middle and right: Digested bauxite solution (Bayer liquor). Note that the digested solution is turbid due to the presence of precipitated iron componds (iron hydroxide).

Titration of Bayer liquor with hydrochloric acid:

• Addition of excess sodium gluconate (NaGluc):

Al(OH)4- + NaGluc → Al(OH)3Gluc- + NaOH

• Titration with 1 mol/L hydrochloric acid, HCl:

1st Equivalence point:

OH- + H3O+ → 2 H2O

CO32- + H+ → HCO3

-

2nd Equivalence point:

HCO3- + H3O+ → CO2 + 2 H2O

• Addition of excess potassium fluoride:

Al(OH)3Gluc- + 6KF → K3AlF6 + 3KOH + Gluc-

• The released KOH is titrated with 1 mol/L HCl:

OH- + H3O+ → 2 H2O

Digestion of bauxite:

Generally, a freshly prepared NaOH solution does not contain carbonate. Thus, only one equivalence point can be detected in the first titration with HCl. Carbonate is formed in alkaline solution due to intake of CO2 during a long exposition time to air. To reproduce two equivalence points, the synthetic Bayer liquor was spiked with 10 mL sodium carbonate solution (approx. 3 g Na2CO3/60 mL).


http://en.wikipedia.org/wiki/Silica

http://en.wikipedia.org/wiki/Iron_oxide

http://en.wikipedia.org/wiki/Iron_oxide

http://en.wikipedia.org/wiki/Titanium_dioxide


Method

001 Title


Compatible with T70 / T90

ID m466

Title Aluminum content in bauxite


Date/Time 23.07.2010 16:23:20

Modified at 23.07.2010 16:23:20


Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 --


Volume [ml] 5.0

Density 1.0 g/mL


Temperature 25.0°C


Type Rondo/Tower A


Lid handling No


Titrant Na-gluconate

Concentraition [mol/L] 25

Volume [mL] 10

Dosing rate [ml/min] 60

Condition No

005 Stir

Speed [%] 30

Duration [s] 120

Condition No


Titrant

Titrant HCl


Sensor

Type pH

Sensor DG115-SC

Unit pH



Stir

Speed [%] 30

Predispense

Mode Volume

Volume [ml] 30

Waiting time [s] 15

Control

Control User


dE (set value)[mV] 6

dV (min)[ml] 0.002

dV (max)[ml] 0.2


dE[mV] 0.5

dt[s] 1

t (min)[s] 3.0

t (max)[s] 30.0


Procedure Standard

Threshold[pH/ml] 0.5

Tendency Negative

Ranges 0


Termination

At Vmax [ml] 60

At potential Yes

Potential [pH] 6

Termination tendency Negative

At slope No

After number of

recognized EQPs Yes

Number of EQPs 2


criteria No


Condition No


Titrant KF


Volume [mL] 10

Dosing rate [ml/min] 60

Condition No

008 Stir

Speed [%] 30

Duration [s] 180

Condition No


Titrant

Titrant HCl


Sensor

Type pH

Sensor DG115-SC

Unit mV



Stir

Speed[&] 30

Predispense

Mode None

Waiting time [s] 0

Control

Control User


dE (set value)[mV] 8.0

dV (min)[ml] 0.005

dV (max)[ml] 0.2


dE[mV] 0.5

dt[s] 1

t (min)[s] 3.0

t (max)[s] 30.0


Procedure Standard

Threshold[mV/ml] 5

Tendency Positive

Ranges 0

Add. EQP criteria Steepest jump

Steepest jumps 1

Termination

At Vmax[ml] 5

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQPs 1


criteria No


Condition No

010 Rinse


Rinse cycles 1



Drain No

Condition No

011 Conditioning

Type Fix

Interval 1


Time [s] 60

Speed [%] 30

Condition No

012 Calculation R1

Result Free Caustic NaOH

Result unit g/L

Formula R1=(Q-Q2)*C/m

Constant C= M/z

M M[Sodium hydroxide]

z z[Sodium hydroxide]

Decimal places 2

Result limits No



Send to buffer No

Condition No

013 Calculation R2

Result Free Carbonate CaCO3

Result unit g/L


Formula R2=Q2*C/m

Constant C= M/z

M M[Calcium carbonate]

z z[Calcium carbonate]

Decimal places 2

Result limits No



Send to buffer No

Condition No

014 Calculation R3

Result Content Al(OH)3 (g/L)

Result unit g/L

Formula R3=(Q[2]+QEX)*C/m

Constant C= M/z

M M[Aluminum trihydroxide]

z z[Aluminum trihydroxide]

Decimal places 2

Result limits No



Send to buffer No

Condition No

015 Calculation R4

Result Content Al(OH)3 (mg/g)

Result unit mg/g

Formula R4=((Q[2]+QEX)*C/30.23)*100

Constant C= M/z

M M[Aluminum trihydroxide]

z z[Aluminum trihydroxide]

Decimal places 2

Result limits No



Send to buffer No

Condition No

016 Calculation R5

Result Content AL2O3 (%)

Result unit %

Formula R5=(R4/10)*C

Constant C= 1.30717

M M[None]

z z[None]

Decimal places 2

Result limits No



Send to buffer No

Condition No

017 End of sample

018 Park



Condition No

Calculation R4: 30.23 = sample size of bauxite powder 100 = dilution factor (5 mL -> 500 mL) Calculation R5: 1.30717 = M(Al2O3)/M(Al(OH)3) = 101.96/78.00


Determination of Boric Acid in Acidic HCl/HF Solutions Boric acid is determined by titration with sodium hydroxide after addition of mannitol. The titration is monitored by a combined pH glass electrode.

Preparation and Procedures - 5 mL acidic bath is diluted with 50 mL deionized

water.

- The sample is titrated with sodium hydroxide to pH 7 (= 0 mV).

- This gives the total acid content (HCl, HF) present in the sample.

- 20 mL mannitol solution is automatically added to the sample beaker by means of an additional burette.

- The sample solution is stirred for 20 s or during a longer time to allow for a complexation reaction between mannitol and boric acid.

- The complexation reaction leads to a release of hydrogen ions.

- These ions can be titrated with 0.1 mol/L NaOH.

Remarks

- The method was developed on a DL70 titrator and has been adapted for T50/T70/T90 Titration Excellence.

- Boric acid is a weak monobasic acid in aqueous solutions. Thus, it cannot be directly titrated using a strong base.

- Mannitol, C6H8(OH)6 , forms a stable 1:1 complex with boric acid:

B(OH)3 + M → B(OH)2O-M- + H+

- The released hydrogen ions can be titrated with sodium hydroxide solution.

In general:

- The addition of mannitol solution allows to avoid volatilization of boron in sample solutions, and to increase the dissociation strength to achieve optimum titration conditions (For more detailed information, see Literature under “Comments”).

Sample Acidic bath, 5 mL

Compound - Boric acid, B(OH)3 M = 61.83, z = 1

- Hydrochloric acid, HCl - Hydrofluoric acid, HF

Chemicals - 50 mL deionized water, - 20 mL mannitol solution,

C6H8(OH)6 , c(C6H8(OH)6) = 200 g/L

Titrant Sodium hydroxide, NaOH, c(NaOH) = 0.1 mol/L

Standard Potassium hydrogen phthalate, KHP, see e.g. M002

Indication DGi112-SC or DGi114-SC combined pH glass electrode with movable sleeve

Chemistry Simplified reaction scheme:

B(OH)3 + M → B(OH)2O-M- + H+

H3O+ + NaOH → 2 H2O + Na+

where M = C6H8(OH)6

Calculation Content boric acid (g/L):

R = Q*C/m

C = M/z

Waste disposal

Neutralization with hydrochloric acid before final disposal

Author, Version

Dieter Rehwald, MT-Germany,1989 Rev. February 2010 / C. De Caro


Instruments - DL70 Titrator - Balance, e.g. XS205

Other titrators: This method can also be run with the T50/T70/T90 Titration Excellence, and with the DL55, DL58, DL70ES, and DL77 instruments. Minor changes in the methods are required.

Accessories - 2 x 10 mL DV1010 burettes - Additional dosing unit (Tx) ME-51109030, or burette drive (DL5x, DL7x) - PP titration beaker ME-101974 - Printer

Results METTLER DL70 Titrator A001 Borsäure Measured 14-Nov-1989 12:44 14-Nov-1989 12:28 Titrator SW Version 1.2 User **** RESULTS No ID1 Volume Results 1/1 4711 5.0 mL 5.179 mL ml HCl/HF 9.245 mL ml Brsaeure 11.43 g/L Content

Titration curve



Table of measured values Not available

Comments

• Boric acid is used in various market segments and for the most different applications such as e.g. antiseptic, flame retardant, and in nuclear power plants to control the rate of fission. In electroplating and semiconductor industry it is used among other purposes for e.g. surface treatment and metal processing (e.g. nickel baths, boron metal alloys).

• The acid dissociation constant pKa of boric acid B(OH)3 is 9.14 at 25°C, thus it is a rather weak acid.

• Boric acid does not dissociate in aqueous solution, but is acidic due to its interaction with water molecules, forming tetrahydroxyborate ions:

B(OH)3 + H2O → B(OH)4- + H+ Ka = 5.8x10−10 mol/l; pKa = 9.24

However, the dissociation is not so strong, and therefore the released hydrogen ions can not be directly titrated with a strong base.

Literature:

- METTLER TOLEDO Application Brochure No. 1, “18 Customer Methods””, ME-724492, 1992.

- T. Ishikawa, E. Nakamura, “Formation of Boron-mannitol Complex in the Hydrofluoric Acid Solution and a Possibility of the Use of Acids in the Separation of Boron from the Natural rock Samples”, Proc. Japan Acad. 66 No.5 (Ser. B), p. 91, 1990.

- P. M. Williams and P. M. Strack, “Complexes of Boric Acid with Organic Cis-Diols in Seawater”, Limnology and Oceanography, Vol. 11, No. 3, pp. 401-404, 1966.

- P. A. Webster, “Determination of Boric Oxide in Glass by Direct Titration”, Journal of the American Ceramic Society, Volume 34 Issue 10, pp 305-309, 1951.

- Max Hollander, William Rieman, “Titration of Boric Acid in Presence of Mannitol”, Ind. Eng. Chem. Anal. Ed. 17 (9), pp 602–603, 1945.


Method DL70 Titrators:

Title

Method ID ........................... A001

Title ............................... Borsäure

Date/time ........................... 14-Nov-1989 12:28

Sample

Number samples ...................... 1

Titration stand ..................... Stand 1

Entry type .......................... Volume U

Lower limit [mL].................. 1.0

Upper limit [mL].................. 10.0

ID1 ................................. 4711

Molar mass M ........................ 61.83


Stir

Speed [%] ........................... 50

Time [s] ............................ 10

Titration

Titrant ............................. NaOH


Sensor .............................. DG112-SC

Unit of meas. ...................... mV

Titration mode ...................... EP


Volume [mL] .................... 1.0

Titrant addition .................... Dynamic

dE(set) [mV] ................... 8.0

dV(min) [mL] ................... 0.02

dV(max) [mL] ................... 0.1

dE [mV] ........................ 0.5

dt [s] ......................... 0.5

t(min) [s] ..................... 2.0

t(max) [s] ..................... 20.0

Endpunktart ......................... EPA

Potential [mV,pH,…] ............ 0.0

Tendency ............................ Negative


Calculation

Result name ......................... mL HCl/HF

Formula ............................ R=VEQ

Constant ............................ C=1

Result unit ......................... mL

Decimal places ...................... 3

Record

All results ......................... Yes

Table of measured values ............ Yes

E – V curve ......................... Yes

Dispense

Titrant ............................. Mannit


Volume [mL] ......................... 20.0

Stir

Speed [%] ........................... 50

Time [s] ............................ 20

Titration

Titrant ............................. NaOH


Sensor .............................. DG112-SC

Unit of meas. ...................... mV

Titration mode ...................... EQP


Volume [mL] .................... 1.0

Titrant addition .................... DYN

dE(set) [mV] ................... 8.0

Limits dV ...................... Absolute

dV(min) [mL]................. 0.02

dV(max) [mL]................. 0.2

Measure mode ....................... EQU

dE [mV] ........................ 1.0

dt [s] ......................... 1.0

t(min) [s] ..................... 3.0

t(max) [s] ..................... 30.0

Threshold ........................... 20.0


Evaluation procedure ................ Standard

Calculation

Result name ......................... mL Brsaeure

Formula ............................ R2=VEQ[2]+VEX[1]

Constant ............................ C2=1

Result unit ......................... mL

Decimal places ...................... 3

Calculation

Result name ......................... Content

Formula ............................ R3=(Q[2]+QEX[1])*C3/U

Constant ............................ C3=M/z

Result unit ......................... g/L

Decimal places ...................... 2

Record

All results ..........................Yes

Table of measured values .............Yes

E – V curve ..........................Yes

--------------------------------------------------------------

Titration Excellence:

001 Title



ID m222

Title Boric acid


Date/Time 01.02.2010 08:00:00

Modified at 01.02.2010 08:00:10


Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Acidic solution

Entry type Volume

Lower limit 1.0 mL

Upper limit 10.0

Density 1.0 g/mL


Temperature 25.0°C

Entry Before


Type Manual stand


004 Stir

Speed 50%

Duration 10 s

Condition No

005 Titration (EP) [1]

Titrant

Titrant NaOH


Sensor

Type pH

Sensor DG115-SC

Unit mV



Stir

Speed 35%

Predispense

Mode Volume

Volume 1.0

Waiting time 10 s

Control

End point type Absolute

Tendency Negative

End point value 0.0 mV

Control band 100.0 mV

Dosing rate(max) 10 mL/min

Dosing rate(max) 10 µL/min

Termination

At EP Yes

Termination delay 10 s

At Vmax 10.0 mL

Max. time infinity

006 Calculation R1

Result Consumption HCl/HF

Result unit mL

Formula R1 = VEQ[1]

Constant C= 1

M M[None]

z z[None]

Decimal places 3

Result limits No


007 Record

Summary No

Results Per sample

Raw results No

Table of meas. values Yes


Sample data No

Resource data No

E - V Yes

dE/dV - V No

log dE/dV - V No

d2E/dV2 - V No

BETA – V No

E - t No

V - t No

dV/dt - t No

T – t No



Method No

Series data No

Condition No


Titrant Mannitol

Concentration 1

Volume 20.0 mL


Condition No

009 Stir

Speed 50%

Duration 20 s

Condition No


Titrant

Titrant NaOH


Sensor

Type pH

Sensor DG115-SC

Unit mV



Stir

Speed 35%

Predispense

Mode Volume

Volume 1.0

Waiting time 10 s

Control

Control User



dV(min) 0.02 mL

dV(max) 0.2 mL


dE 1.0 mV

dt 1 s

t (min) 3 s

t (max) 30 s


Procedure Standard

Threshold 20

Tendency Negative

Ranges 0


Termination

At Vmax 20.0 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQPs 1

011 Calculation R2

Result Consumption boric acid

Result unit mL

Formula R2 = VEQ[2]+VEX[1]

Constant C= 1

M M[None]

z z[None]

Decimal places 3

Result limits No


012 Calculation R3

Result Boric acid content

Result unit g/L

Formula R3 = (Q[2]+QEX[1])*C/m

Constant C= M/z

M M[B(OH)3]

z z[B(OH)3]

Decimal places 2

Result limits No


013 Record

Summary No

Results Per sample

Raw results No

Table of meas. values Yes

Sample data No

Resource data No

E - V Yes

dE/dV - V No

log dE/dV - V No

d2E/dV2 - V No

BETA – V No

E - t No

V - t No

dV/dt - t No

T – t No



Method No

Series data No

Condition No

014 End of sample


Titanium Content in Mining Solutions Determination of titanium content in titanium ore digestion and purification solution.

Preparation and Procedures

CAUTION: Work with a lab coat, and wear gloves and safety goggles.

- Depending on the expected concentration of Ti3+ in the sample solution, the amount of sample is chosen in such a way that the final amount of Ti3+ in the titration vessel is ~ 0.5 mmol. This leads to a titrant consumption of ~ 5 mL, which is approximately half the burette volume.

- To the sample solution 40 mL deionised water and ~ 10 mL concentrated sulfuric acid are added to make the sample solution acidic enough for the redox reaction between iron and titanium to take place.

Remarks

- The parameters have been optimized for this specific sample. It may be necessary to adapt the method to your sample.

- Since Ti3+ is a very unstable species, the sample solution should always be prepared freshly.

- Also make sure to add the titanium solution to the titration beaker only directly before the titration itself. Otherwise loss of titanium can be observed within one sample series because of oxidation by air. The use of an inert gas such as nitrogen could be recommended.

- Please take care when handling the concentrated sulfuric acid as this will cause severe burns when in contact with skin.

Sample Digestion solution from titanium ore (e.g. TiO2) ~ 5 mL

Compound Titanium, Ti3+, M = 47.867 g/mol, z = 1

Chemicals 40 mL deionized water 10 mL concentrated H2SO4

Titrant Ferric ammonium sulfate, NH4Fe(SO4)2 (Fe(III)AS) c(NH4Fe(SO4)2) = 0.1 M

Standard Ascorbic acid, C6H8O6


Chemistry Fe3+ + Ti3+ → Fe2+ + Ti4+

Calculation Ti-Content (g/L): R1 = Q*C/m C = M/z Content (mol/L): R2 = Q*C/m C = 1/z

Waste disposal

After neutralization of the acid dispose the sample solution as heavy metals.

Author, Version

Melanie Nijman, MSG Anachem, June 2010


Instruments - T50/T70/T90 Titration Excellence - Balance, e.g. XS205 - Rondo 20 sample changer

Accessories - 1 x 10 mL DV1010 burette - PP Titration beakers ME-101974 - LabX pro titration software

Results

Samples 1/6 Titanium solution 5.0 mL 2/6 Titanium solution 5.0 mL 3/6 Titanium solution 5.0 mL 4/6 Titanium solution 5.0 mL 5/6 Titanium solution 5.0 mL 6/6 Titanium solution 5.0 mL Results Comment / ID Rx Result Unit Name

1/6 Titanium solution R1 = 4.1367 g/L Content R2 = 0.08642 mol/L Content 2/6 Titanium solution R1 = 4.1726 g/L Content R2 = 0.08717 mol/L Content 3/6 Titanium solution R1 = 4.1402 g/L Content R2 = 0.08649 mol/L Content 4/6 Titanium solution R1 = 4.1297 g/L Content R2 = 0.08628 mol/L Content 5/6 Titanium solution R1 = 4.1821 g/L Content R2 = 0.08737 mol/L Content 6/6 Titanium solution R1 = 4.1518 g/L Content R2 = 0.08674 mol/L Content Statistics

Rx Name n Mean value Unit s srel [%] R1 Content 6 4.1522 g/L 0.0210 0.505 R2 Content 6 0.08675 mol/L 0.00044 0.505

Titration curve




Volume Increment Signal Change 1st deriv. Time mL mL mV mV mV/mL s 0.0000 NaN 127.3 NaN NaN 0 0.0200 0.0200 15.0 -112.3 NaN 36 0.0400 0.0200 -55.7 -70.7 NaN 66 0.0600 0.0200 -67.9 -12.2 NaN 86 0.1100 0.0500 -68.1 -0.2 NaN 89 0.2350 0.1250 -67.0 1.1 -164.84 92 0.5475 0.3125 -62.5 4.5 -17.93 96 1.0475 0.5000 -55.6 6.9 13.16 100 1.5475 0.5000 -49.7 5.9 15.36 104 2.0475 0.5000 -43.9 5.8 13.92 108 2.5475 0.5000 -35.7 8.2 14.57 113 3.0300 0.4825 -21.8 13.9 24.96 117 3.1870 0.1570 -31.5 -9.7 32.84 136 3.2480 0.0610 -29.6 1.9 35.89 138 3.4005 0.1525 -20.5 9.1 47.54 142 3.4695 0.0690 -18.9 1.6 53.25 157 3.6420 0.1725 -2.0 16.9 99.88 162 3.6620 0.0200 -2.0 0.0 98.15 168 3.7120 0.0500 1.2 3.2 116.80 180 3.7440 0.0320 4.5 3.3 122.92 188 3.7900 0.0460 10.4 5.9 148.23 196 3.8415 0.0515 20.3 9.9 220.52 210 3.8695 0.0280 27.0 6.7 259.63 221 3.8960 0.0265 34.4 7.4 296.47 232 3.9205 0.0245 41.4 7.0 355.89 244 3.9475 0.0270 51.6 10.2 457.57 257 3.9675 0.0200 61.2 9.6 597.72 260 3.9875 0.0200 70.0 8.8 705.32 269 4.0075 0.0200 91.5 21.5 765.55 272 4.0275 0.0200 111.4 19.9 849.06 275 4.0475 0.0200 133.1 21.7 932.52 278 4.0675 0.0200 140.1 7.0 1200.09 291 4.1175 0.0500 206.2 66.1 1654.10 304 4.1375 0.0200 254.7 48.5 1851.92 308 EQP1 4.1388 NaN 257.2 NaN 1915.87 NaN 4.1575 0.0200 292.5 37.8 1856.88 313 4.1775 0.0200 344.2 51.7 1544.28 343 4.1975 0.0200 365.0 20.8 1098.89 351 4.2175 0.0200 376.4 11.4 797.07 354 4.2430 0.0255 387.0 10.6 593.63 357 4.2695 0.0265 394.7 7.7 NaN 360 4.3085 0.0390 402.4 7.7 NaN 363 4.3685 0.0600 410.9 8.5 NaN 366 4.4470 0.0785 419.7 8.8 NaN 370 4.5365 0.0895 426.5 6.8 NaN 373

Comments

--


Method 001 Title



ID MNxxxE

Title Titanium content


Date/Time 01/06/2010 18:11:34

Modified at 02/06/2010 08:45:39


Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Titanium Solution


Volume [mL] 5.0

Density [g/mL] 1.0


Temperature [°C] 25.0°C

003 Titration stand (Rondo/TowerA)

Type Rondo/Tower A


Lid handling No

004 Stir

Speed [%] 30

Duration [s] 10

Condition No


Titrant

Titrant F(III)AS


Sensor

Type mV

Sensor DM140-SC

Unit mV



Stir

Speed [%] 30

Predispense

Mode None

Wait time [s] 5

Control

Control User



dV (min) [mL] 0.02

dV (max) [mL] 0.2


dE [mV] 0.5

dt [s] 2

t (min) [s] 3

t (max) [s] 10


Procedure Standard


Tendency None

Ranges 0


Termination

At Vmax [mL] 10.0

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQPs 1


criteria No


Condition No

007 Calculation R1

Result Content

Result unit g/L

Formula R1=Q*C/m

Constant C= M/z

M M[Titanium]

z z[Titanium]

Decimal places 4

Result limits No



Send to buffer No

Condition No

008 Calculation R2

Result Content

Result unit mol/L

Formula R2=Q*C/m

Constant C= 1/z

M M[Titanium]

z z[Titanium]

Decimal places 5

Result limits No



Send to buffer No

Condition No

009 Rinse


Rinse cycles 1



Drain No

Condition No

010 Conditioning

Type Fix

Interval 1


Time [s] 10

Speed [%] 30

Condition No

011 End of sample

METTLER TOLEDO Application M458-2010 Determination of Cobalt Content in Alloys

The cobalt content in alloys is determined by redox titration in strong acid solution with potassium hexacyanoferrate K3Fe(CN)6 as a titrant. The potential change is monitored by a combined platinum ring electrode.


A too low pH value leads to the formation of HCN gas which is toxic. Thus, work in a fume hood, use safety goggles and wear gloves. Sample dissolution: - 0.15 g metallic alloy is placed in a suitable

container for dissolution e.g. a platin crucible. - 5 mL concentrated nitric acid is added,

together with 2-3 mL hydrofluoric acid. - The solution is heated until alloy is dissolved. - After cooling down to room temperature, 10-15

mL deionized water is added. - The sample solution in poured into a

polypropylene titration beaker. Cobalt is now present as Co(II)

Titration: - 10 mL 50% ammonium citrate is added to the

sample - 20 mL ammonium hydroxide solution is added

to the sample. - Add 10-20 mL deionized water. - Start titration.

Remarks


- Clean the electrode thoroughly after each sample. If necessary, clean the metal ring of the electrode with a paper tissue.

Literature:

- ISO 9389:1989 (E), “Nickel alloys- Determination of cobalt content – Potentiometric titration with potassium hexacyanoferrate(III)”, www.iso.org .

- H. Poppe, G. Den Boef, “Photometric titration of cobalt with hexacyanoferrate(III)”, Talanta, Vol. 12, Issue 6, 1965, pp 625-637.

- E. Norkus, “Potentiometric titration of Co(II) in presence of Co(III)”, Talanta, Vol. 47 (1998), pp 1297-1301.

Sample Metal alloy, 0.15 g 6-13% Co content

Compound Cobalt, Co M = 58.933; z = 1

Chemicals 85% Nitric acid, HNO3

48% Hydrofluoric acid, HF

50% Ammonium citrate, (NH4)3C6H5O7

30% Ammonium hydroxide, NH4OH

Deionized water

Titrant Potassium hexacyanoferrate, K3 Fe(CN)6, c(KFe(CN)6) = 0.017 mol/L

Standard Cobalt chloride, CoCl2

Indication DMi140-SC combined redox electrode

Chemistry Co(NH3)62+ + Fe(CN)6

3- → Co(NH3)6

3+ + Fe(CN)64-

Simplified: Co2+ + Fe 3+ → Co3+ + Fe2+

Calculation Content (DL5x) • R1 = Q*C/m • C = M/(10*z)

Waste disposal

Cyanide solutions. CAUTION: Cyanide is toxic!

Author, Version

Lee Hyun Jung, MT-Korea, Dec 2003 Revised January 2010 / C. De Caro


http://www.iso.org/


Instruments - DL50 Graphix Titrator - AT261 Balance This method can also be run with the G20 and T50/70/90 Titration Excellence (minor

adaptations in their method), and with the DL53/DL55/DL58, and DL67/70ES/77 instruments.

Accessories - 1 x 10 mL DV1010 burette - Titration beaker ME-101974 - Printer

Results Alloy Theoretical Results Std. srel Comments Co-content deviation % % % % G10E 6.0 5.964 Ammonium citrate: 7.5 mL 5.952 Ammonium hydroxide: 17.5 mL 5.956 5.973 Average: 5.961 0.009287 0.156 KPM25P 10.2 9.888 Ammonium citrate: 7.5 mL 10.091 Ammonium hydroxide: 17.5 mL 10.018 9.972 10.012 Average: 9.996 0.07417 0.742 CN20 7.8 7.375 Ammonium citrate: 7.5 mL 7.086 Ammonium hydroxide: 17.5 mL 6.869 6.600 6.329 Average: 6.852 0.407924 5.954 FA1 13.0 12.821 Ammonium citrate: 7.5 mL 12.576 Ammonium hydroxide: 17.5 mL 12.541 12.548 12.316 Average: 12.560 0.179177 1.426 12.814 Ammonium citrate: 10 mL 12.807 Ammonium hydroxide: 20 mL 12.844 12.845 Average: 12.828 0.019841 0.155

Titration curve

KPM25P sample 1/5


Volume Increment Signal Change 1st deriv. Time mL mL mV mV mV/mL min:s

ET1 0 -125.3 0:03 0.02 0.02 -125.1 0.2 9.7 0:06 0.04 0.02 -125 0.1 6.5 0:09 0.08 0.04 -125 0 0 0:12 … … … … … … … … … … … … 13.52 0.2 -58.5 4.3 21.6 5:01 13.72 0.2 -53.1 5.4 26.8 5:06 13.92 0.2 -47 6.1 30.4 5:12 14.12 0.2 -38.9 8.1 40.7 5:19 14.276 0.156 -30.7 8.2 52.6 5:26 14.4 0.124 -22 8.7 69.8 5:34 14.491 0.091 -14.2 7.9 86.6 5:42 14.568 0.077 -6 8.1 105.7 5:51 14.632 0.064 2.1 8.1 126.2 5:59 14.686 0.054 10.3 8.2 152 6:09 14.731 0.045 17.8 7.5 166.6 6:18 14.775 0.044 26.1 8.3 189.5 6:25

EQP1 14.812 0.037 34.3 8.2 221.8 6:34 14.843 0.031 41.1 6.8 218.9 6:43 14.88 0.037 49.2 8.1 218.3 6:51

KPM25P sample 1/5



Comments

Redox potential of cobalt (acidic solution) Co2+ + 2 e- = Co E = - 0.277 V Co3+ + e- = Co2+ E = + 1.808 V

Co2+ ion is stable in acidic solution.

Additional titration methods for the determination of cobalt

1. Redox titration of Co(II): Oxidation of Co(II) to Co(III) with a known excess of sodium chromate (Na2CrO4) and back titration with iron(II) ammonium sulfate, (NH4) 2FeSO4. Indication: DMi140-SC (combined platinum ring electrode) Reagents: - Sodium chromate (Na2CrO4), 0.033 mol/L - Iron(II) ammonium sulfate (NH4) 2FeSO4 , 0.1 mol/L - Ethylenediamine C2H4(NH2)2 , 0.1 mol/L - Sulfuric acid 50%, H2SO4 Procedure: Add to sample 10 mL 0.1 mol/L ethylenediamine, 4 mL 0.033 mol/L sodium chromate, and 5 mL 50% sulfuric acid. Titrate with 0.1 mol/L (NH4) 2FeSO4 (Determ. limits: 25 mg Co per sample).

2. Precipitation titration of Co(II) Precipitate Co(II) with an excess of cyanide solution and back titrate the cyanide excess with silver nitrate. Indication: DMi141-SC (combined silver ring electrode) Reaction: - Precipitation of Co(II) with an excess of cyanide: Co2+ + 5 CN- → [Co (CN)5]3- - Back titration of cyanide excess (two-step titration): Ag+ + 2 CN- → [Ag (CN)2]- [Ag (CN)2]- + Ag+ → 2 AgCN The titration curve shows two inflection points corresponding to the two steps of titration reaction. A soluble complex Ag(CN)2

- is first formed by the reaction between silver and cyanide ion:

Ag+ + 2 CN- → [Ag (CN)2]-

As long as free cyanide is still present, the solution remains clear. First excess of silver ions causes formation of a white precipitate indicating the equivalence point:

Ag+ + [Ag(CN)2]-→ Ag[Ag(CN)2]

1 mole Ag-ions : 2 moles CN-ions. A factor 2 has to be included in the calculation (see M196). Procedure: Dilute the sample in 50 mL water and add 20 mL 0.1 mol/L potassium cyanide KCN. Back titrate with 0.1 mol/L silver nitrate AgNO3 to the second EQP. 3. Complexometric titration of Co(III/II)

Direct titration of cobalt Co3+ is performed in ammonia-containing solution with EDTA and murexide as indicator. The endpoint is given by a sharp color change from yellow to red/violet. Indication: Photometric sensor, e.g. DP5 Phototrode™ at 520 nm. Procedure: The pH of the acidic cobalt solution (max. 25 mg/100 mL sample) is adjusted to approximately pH 6. Subsequently, murexide is added to the sample beaker, whereby an orange color is appearing. Ammonia solution is added until the color has changed to yellow. The solution has to be slightly basic (e.g. pH 8). At that point, the sample solution is titrated with EDTA. During titration, the solution becomes acidic due to release of hydrogen ions H+ from EDTA, and the color is vanishing back from yellow to orange. To avoid it, it is necessary to add some drops of ammonia during titration to get back the yellow color. Important: do not add too much ammonia since amine complexes of cobalt are formed.


Method DL5x Titrator

Method 1 Cobalt II

Version 03-Dec-2003 8:35

Title

Method ID .......................... 1

Title .............................. Cobalt II

Date/time .......................... 03-Dec-2003 8:35

Sample

Sample ID ..........................


Lower limit [g] ................ 0.0

Upper limit [g] ................ 2.0

Molar mass M ....................... 58.933




Stir

Speed [%] .......................... 40

Time [s] ........................... 20

EQP titration

Titrant/Sensor

Titrant ........................ K3Fe(CN)6


Sensor ......................... DM140-SC

Unit of meas. .................. mV

Predispensing ...................... No


dE(set) ........................ 8.0

dV(min) [mL] ................... 0.02

dV(max) [mL] ................... 0.2

Measure mode ....................... Equilibrium controlled

dE [mV] ........................ 0.5

dt [s] ......................... 1.0

t(min) [s] ..................... 3.0

t(max) [s] ..................... 30.0

Recognition

Threshold ...................... 30.0

Steepest jump only ............. No

Range .......................... No

Tendency ....................... Positive

Termination

at maximum volume [mL] ......... 20.0

at potential ................... No

at slope ....................... No

after number EQPs .............. Yes

n = ...................... 1

comb. termination criteria ..... No

Evaluation

Procedure ...................... Standard

Potential 1 ................... No

Potential 2 ................... No

Stop for reevaluation ......... No

Calculation

Formula ........................... R1=Q*C/m

Constant ........................... C1=M/(10*z)

Decimal places ..................... 3

Result unit ........................ %

Result name ........................ Co content

Statistics ........................ Yes

Calculation

Formula ........................... R2=VEQ

Constant ...........................

Decimal places ..................... 3

Result unit ........................ mL

Result name ........................ Consumption

Statistics ........................ No

Report


Results ............................ Yes

All results ........................ Yes

Raw results ........................ No

Table of measured values ........... Yes

Sample data ........................ No

E - V curve ........................ Yes

dE/dV – V curve .................... Yes

d2E/dV2 – V curve ................... No


E – t curve ........................ No

V – t curve ........................ No

dV/dt - t curve ................... No


001 Title



ID 1

Title Cobalt II


Date/Time 01.03.2010 15:00:00

Modified --

Modified by --

Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 -- 1

Entry type Weight

Lower limit 0.0 g

Upper limit 2.0 g

Density 1.0 g/mL


Temperature 25.0°C


Type Manual stand


004 Stir

Speed 40%

Duration 20 s


Titrant

Titrant K3Fe(CN)6


Sensor

Type mV

Sensor DM140-SC

Unit mV



Stir

Speed 40%

Predispense

Mode None

Wait time 0 s

Control

Control User


dE(set) 8.0

dV(min) 0.02 mL

dV(max) 0.2 mL


dE 0.5 mV

dt 1.0 s

t(min) 3.0 s

t(max) 30.0 s


Procedure Standard

Threshold 30 mV/mL

Tendency Positive

Ranges 0


Termination

At Vmax 20.0 mL

At potential No

At slope No

After number of

recognized EQPs No


criteria No

006 Calculation R1

Result Co content

Result unit %

Formula R=Q*C/m

Constant C=M/(10*z)

M M[Co]

z z[Co]

Decimal places 3

...

007 Calculation R2

Result Consumption

Result unit mL

Formula R2=VEQ

Constant C=1

M M[None]

z z[None]

Decimal places 3

...

008 Record

. . . .

009 End of sample


Determination of Uranium according to Modified Davies-Gray Method Uranium is determined by indirect titration using potassium dichromate according to the modified method of Davies and Gray. This application has been developed based on standard ASTM C1267-06, but it does not replace the standard used.

Preparation and Procedures CAUTION: Work under appropriate safety conditions.

See “Comments” for preparation of reagents. The dispensing of reagents is completely automated:

- 2 mL acid sample are added into the titration beaker. Uranium is present as UO2

2+ (VI) or UO2+ (IV) in solution.

- 2.5 mL sulphamic acid is added by a burette. Sulphamic acid destroys nitrous acid which can interfere (reducing agents).

- A second burette dispenses 15 mL H3PO4/Fe(II) solution. Ferrous ions reduce U6+ to U4+. Concentrated phosphoric acid complexes U6+ to force completion of reaction.

- A third burette dispenses 3.4 mL HNO3/Sulphamic acid/Molybdate solution. Excess Fe(II) is destroyed using concentrated nitric acid with ammonium molybdate acting as a catalyst. This leads to NO and NO2 which are neutralized with sulphamic acid.

- After 300 s of stir time, 34 mL H2SO4/vanadyl solution is added to the sample by means of a peristaltic pump.

- All uranium is now present as U4+. This could be titrated directly with dichromate but the kinetics is very slow. Thus, vanadyl solution is added to the sample solution. U4+ reacts with vanadyl, VO2+ giving V3+.

- V3+ can be now titrated with potassium dichromate according to equation 2 (see “Chemistry”).

Remarks

Literature: 1. ASTM C1267-06,

“Standard Test Method for Uranium by Iron (II) Reduction in Phosphoric Acid Followed by Chromium (VI) Titration in the Presence of Vanadium”, 2006.

2. ISO 7097-1:2004, “Nuclear fuel technology -- Determination of uranium in solutions, uranium hexafluoride and solids -- Part 1: Iron(II) reduction/potassium dichromate oxidation titrimetric method”, 2004.

3. Davies, W., Gray, W., Talanta 11 (1964), p. 1203. 4. Eberle, A.R., Lerner, M.W., Goldbeck, C.G., Rodder,

C.J., NBL Report 252 (1970). 5. Karekar, C.V., Chander, K., Nair, G.M., Natarajan,

P.R., J. Radioanal. Nucl.Chem.Letters 107(5), pp. 297-305, 1986.

Sample Uranium solution -U(VI), U(IV)- , 2 mL

Compound Uranium, U M = 238.03 g/mol , z = 1

Chemicals - 1 and 1.5 M Sulfamic acid, (NH2)SO3H - 85% Orthophosphoric acid, H3PO4 - 70% Nitric acid (sp. gr. 1.42), HNO3 - Iron(II)sulfate hydrate, FeSO4*7H2O, - 98% Sulfuric acid (sp. gr. 1.84) H2SO4, - Vanadyl sulfate, VOSO4, - Ammonium molybdate,

(NH4)6Mo7O24*4H2O

Titrant Potassium dichromate, K2Cr2O7

c(⅓ K2Cr2O7) = 0.0135 mol/L

Standard (CH2NH3)2SO4*FeSO4*4H2O (see M031, Brochure 9)


Chemistry 1) Reaction of V with U4+: U4+ + 2 VO2+ → UO2

2+ + 2 V3+ 2) Titration of vanadium: Cr2O7

2-+ 6 V3++ 2 H+ → 2 Cr3++ 6 VO2+ + H2O

Calculation U content (g/L): R1 = Q*C/m C = M/z

Waste disposal

Disposal as radioactive waste (uranium waste)

Author, Version

Russel May, MT-AUS, Feb 1994 Revised February 2010



Instruments - T70/T90 Titration Excellence with LabX titration - XS205 Balance

Other titrators: This method can be also run with the DL70ES and DL77 instruments.

Accessories - 4 x 10 mL DV1010 burettes + dosing tube adapter 4 to 1 ME-51108356 - 3 dosing unit ME-51109030 - PP titration beaker ME-101974 - SP250 Peristaltic pump ME-51108016

Comments

Principle: - Uranium samples are generally strong acid solution containing e.g. nitric acid used for dissolution of

the sample. Pure uranium, uranium alloys, UO2 powders and pellets, U3O8, U/Zr, U/Al, and so on can be dissolved using strong acid mixtures of HNO3, HF and HCl in various ratio.

- Dissolved uranium ions are present in the sample solution as U(IV) and U(VI), e.g. U4+ and U6+. - Uranium (VI) is reduced to uranium (IV) by excess iron (II) in concentrated phosphoric acid containing

sulfamic acid. - The excess amount of iron Fe(II) is selectively oxidized by nitric acid (HNO3) in the presence of a

molybdenum(VI) catalyst. - The nitrogen oxides (NO, NO2) formed during reduction of Fe (II) are neutralized by sulfamic acid.

This is necessary since they are reducing agents and thus they interfere with the analysis. - After the addition of a vanadium (IV) solution, uranium (IV) reacts with it leading to vanadium (III).

Vanadium (III) is titrated with chromium (VI) since the direct titration of U (IV) is very slow.

Preparation of reagents: 1. 1 and 1.5 mol/L sulfamic acid solutions, (NH2)SO3H.

Sulfamic acid is used to neutralize nitrogen oxides.

2. Orthophosphoric acid solution, H3PO4: Add 2 mL 0.1 mol/L K2Cr2O7 solution and fill up to 500 mL with 85% H3PO4.

3. Ferrous sulfate solution: - Add 50 mL 98% H2SO4 to 350 mL H2O and stir. - Add 140 g FeSO4*7H2O, stir and cool to room temperature. - Dilute to 500 mL with H2O.

4. 0.9 M sulfuric acid, H2SO4

5. H3PO4/Fe2+ solution: - Add 65 mL of ferrous sulfate solution (3) to 500 mL orthophosphoric acid solution (2), and mix well. This solution reduces all the present U6+ to U4+ with excess Fe2+.

6. 8 M HNO3/Sulfamic acid/Ammonium molybdate solution: - Dissolve 2 g ammonium molybdate in 200 mL H20. - Add 250 mL 70% HNO3 and cool down to room T. - Add 50 mL 1.5 M sulfamic acid. - Dilute to 500 mL with H2O. Nitric acid neutralizes excess Fe(II) and ammonium molybdate acts as a catalyst.

7. 0.9 mol/L H2SO4/VOSO4 solution: - Add 0.5 g VOSO4 to 500 mL 0.9 mol/L H2SO4 .This solution has to be prepared weekly.

8. Potassium dichromate titrant, K2Cr2O7: - M(K2Cr2O7) = 294.185 g/mol , c(1/3 K2Cr2O7) = 0.0135 mol/l - Dissolve approx. 1.32 g in 1 L volumetric flask, and dilute with water up to the mark.


Chemical equations

In concentrated phosphoric acid solution U(VI) is reduced to U(IV):

UO22+ + 2 Fe2+ + 4 H+ → U4+ + 2 Fe3+ + 2 H2O

• Excess iron (II) is selectively oxidized by nitric acid (HNO3) in the presence of a molybdenum(VI) catalyst.

3 Fe2+ + NO3- + 4 H+ → 3 Fe3+ + NO + 2 H2O

Fe2+ + NO3- + 2 H+ → Fe3+ + NO2 + H2O

• The nitrogen oxides (NO, NO2) formed during reduction of Fe(II) are neutralized by sulfamic acid. This is necessary since they are reducing agents and thus they interfere with the analysis.

• After the addition of a vanadium (IV) solution, uranium (IV) reacts with it leading to vanadium (III).

U4+ + 2 VO2+ → UO22+ + 2 V3+

• Vanadium (III) is titrated with chromium(VI) since the direct titration of U(IV) is very slow.

Cr2O72- + 6 V3+ + 2 H+ → 2 Cr3+ + 6 VO2+ + H2O

This reaction is equivalent to:

Cr2O72- + 3 U4+ + 2 H+ → 2 Cr3+ + 3 UO2

2+ + H2O

Therefore: 1 mole Cr2O72- corresponds to 3 mole U4+, and z = 3 for potassium dichromate.

Note:

In diluted phosphoric acid solution the following reactions take place:

U4+ + 2 Fe3+ + 2 H2O → UO22+ + 2 Fe2+ + 4 H+

Fe2+ + VO2+ + 2 H+ → Fe3+ + V3+ + H2O

Therefore, it is necessary that the phosphoric acid solution is highly concentrated.

Additional remarks

- This application allows for the titration of 20 up to 200 mg uranium in a sample.

- Systematic errors can arise if part of the VO2+ is oxidized by air to V5+. To prevent this, the vanadyl solution should be prepared in acid medium and frequently checked for V5+.

- To make sure that no errors can occur due to the presence of nitrogen oxides remaining after the Fe2+-NO3

- reaction (oxidation of Fe(II) to Fe(III) with nitrate ions), a stream of CO2 gas is passed into the sample solution during analysis. This will remove the oxides.

- Eberle (see “Remarks”, Literature ref. no. 4) has adapted the titration method of Davies and Gray to achieve a faster method.

- This method is based on the Modified Davies-Gray titration as given in ASTM Standard C1267-06. This application does not replace the ASTM C1267-06 standard.


Method Titration Excellence

001 Title


Compatible with T70 / T90

ID M292

Title U content


Date/Time 01.03.2010 10:00:00

Modified at 01.03.2010 10:00:10


Protect No

SOP None

002 Sample

Number of IDs 1

ID 1 Uranium

Entry type Volume

Lower limit 0.0 mL

Upper limit 2.0 mL

Density 1.0 g/mL


Temperature 25.0°C

Entry Before


Type Manual stand


004 Dispense

Titrant Sulfamic acid


Volume 2.5 mL


Condition No

005 Stir

Speed 15%

Duration 30 s

Condition No

006 Dispense

Titrant H3PO4/Ferrous


Volume 15.0 mL


Condition No

007 Stir

Speed 30%

Duration 30 s

Condition No

008 Dispense

Titrant HNO3/AmmMolybdate


Volume 3.4 mL


Condition No

009 Stir

Speed 20%

Duration 300 s

Condition No

010 Pump

Auxiliary reagent Sulphuric/vanadyl

Volume [mL] 34.0

Condition No

011 Stir

Speed 70%

Duration 60 s

Condition No


Titrant

Titrant 1/3 K2Cr2O7


Sensor

Type mV

Sensor DM140-SC

Unit mV



Stir

Speed 35%

Predispense

Mode None

Waiting time 0 s

Control

Control User


dE (set value) 8 mV

dV (min) 0.02 mL

dV (max) 0.2 mL


dE 0.5 mV

dt 1 s

t (min) 3 s

t (max) 30 s


Procedure Standard

Threshold 150

Tendency Positive

Ranges 0


Termination

At Vmax 15 mL

At potential No

At slope No

After number of

recognized EQPs Yes

Number of EQPs 1


criteria No



Condition

Condition No

013 Calculation R1

Result U content

Result unit g/L

Formula R1=Q*C/m

Constant C= M/z

M M[Uranium]

z z[Uranium]

Decimal places 5

Result limits No


Extra statistical

functions No

Send to buffer No

Condition No

014 End of sample

Note:

1. The method can be easily modified to be run on T50 and

T70 Titration Excellence instruments.

2. M[Uranium]=238.030 g/mol, z[Uranium]=1

3. M[K2Cr2O7]=294.185 g/mol, z[K2Cr2O7]=3


DL70ES and DL77 Titrators

Method T003 U by Davies Gray

Version 15-Feb-1994 11:50

Title

Method ID . . . . . . . . . . . . . T003

Title . . . . . . . . . . . . . . . U by Davies Gray

Date/time . . . . . . . . . . . . . 15-Feb-1994 11:50

Sample

Number samples . . . . . . . . . . . 1

Titration stand . . . . . . . . . . Stand 1

Entry type . . . . . . . . . . . . . Volume U

Lower limit [mL] . . . . . . . . 0.0

Upper limit [mL] . . . . . . . . 2.0

ID 1 . . . . . . . . . . . . . . . . Uranium

Molar mass M . . . . . . . . . . . . 238.03

Equivalent number z . . . . . . . . 1

Instruction

Instruction . . . . . . . . . . . . Aliquot sample

> . . . . . . . . . . . . . . . . .

> . . . . . . . . . . . . . . . . .

Dispense

Titrant . . . . . . . . . . . . . . Sulphamic acid

Concentration [mol/L] . . . . . . . 1.0

Volume [mL] . . . . . . . . . . . . 2.5

Stir

Speed [%] . . . . . . . . . . . . . 10

Time [s] . . . . . . . . . . . . . . 30

Dispense

Titrant . . . . . . . . . . . . . . H3PO4/Ferrous


Volume [mL] . . . . . . . . . . . . 15.0

Stir

Speed [%] . . . . . . . . . . . . . 30

Time [s] . . . . . . . . . . . . . . 30

Dispense

Titrant . . . . . . . . . . . . . . HNO3/Amm molyb


Volume [mL] . . . . . . . . . . . . 3.4

Stir

Speed [%] . . . . . . . . . . . . . 30

Time [s] . . . . . . . . . . . . . . 300

Pump

Auxiliary reagent . . . . . . . . . Sulphuric /vanad

Volume [mL] . . . . . . . . . . . . 34.0

Stir

Speed [%] . . . . . . . . . . . . . 70

Time [s] . . . . . . . . . . . . . . 60

Titration

Titrant . . . . . . . . . . . . . . K2Cr2O7


Sensor . . . . . . . . . . . . . . DM140-SC

Unit of meas. . . . . . . . . . . . mV

Titration mode . . . . . . . . . . . EQP

Titrant addition . . . . . . . . DYN

dE(set) [mV] . . . . . . . . . 8.0

Limits dV . . . . . . . . . . Absolute

dV(min) [mL] . . . . . . . 0.02

dV(max) [mL] . . . . . . . 0.2

Measure mode . . . . . . . . . . EQU

dE [mV] . . . . . . . . . . . 0.5

dt [s] . . . . . . . . . . . 1.0

t(min) [s] . . . . . . . . . 3.0

t(max) [s] . . . . . . . . . 30.0

Threshold . . . . . . . . . . . . 150.0

EQP range . . . . . . . . . . . . Yes

Limit A [mV,pH,...] . . . . . -1000

Limit B [mV,pH,...] . . . . . 1000

Maximum volume [mL] . . . . . . . 15.0

Termination after n EQPs . . . . Yes

n = . . . . . . . . . . . . . 1

Evaluation procedure . . . . . . Standard

Steepest jump only . . . . . . . Yes

Calculation

Result name . . . . . . . . . . . . Uranium

Formula . . . . . . . . . . . . . . R=(Q*C)/U

Constant . . . . . . . . . . . . . . C=M/z

Result unit . . . . . . . . . . . . g/L

Decimal places . . . . . . . . . . . 5

Statistics

Ri (i=index) . . . . . . . . . . . . R1

Standard deviation s . . . . . . . . Yes

Rel. standard deviation srel . . . . Yes

Record

Output unit . . . . . . . . . . . . Printer

Results last sample . . . . . . . . Yes

Remarks:

1. The original version of this method has the following

calculation.

Calculation

Result name . . . . . . . . . . . . Uranium

Formula . . . . . . . . . . . . . . R=VEQ*C/U

Constant . . . . . . . . . . . . . . C=5

Result unit . . . . . . . . . . . . g/L

Decimal places . . . . . . . . . . . 3

With

Titration

Titrant . . . . . . . . . . . . . . K2Cr2O7


2. The content is calculated directly form the titrant

consumption to the EQP (VEQ). Thus, it seems that a

conversion factor in mg U/mL titrant has been used as a

titer for the titrant.

This conversion factor may be given in the constant C=5.

This application bulletin represents selected, possible application examples. These have been tested with all possible care in our lab with the analytical instrument mentioned in the bulletin. The experiments were conducted and the resulting data evaluated based on our current state of knowledge.

However, the application bulletin does not absolve you from personally testing its suitability for your intended methods, instruments and purposes. As the use and transfer of an application example are beyond our control, we cannot accept responsibility therefore.

When chemicals and solvents are used, the general safety rules and the directions of the producer must be observed.

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Selected Applications for Titration

in Metals Mining

This brochure contains dedicated applications for the determination

of metals in various mining samples.

The titration analyses of ferrous and base metals as well as

precious metals such as gold and silver are described in a detailed

and comprehensive way that allows easy adaptation to the specific

sample.

In addition, the titration of auxiliary reagents frequently used

in

mining engineering such as cyanide salts is presented.

METTLER TOLEDO offers you various powerful tools for titration in

metals mining which are meant to facilitate your content

determination analyses and to contribute to reliable results over the

whole lifetime of your instrument.

Appl. Brochure Nr. 42 Metals in the Mining Industry

Documents

Transcript of Appl. Brochure Nr. 42 Metals in the Mining Industry