AIM: TO

ANALYSIS THE

METALS PRESENT IN COINS

CERTIFICATE

This is certify that Ankur Singhal of class XII-B completed this project on

TO ANALYSE THE METALS PRESENT IN INDIAN COINS

in the chemistry lab of D.L. D.A.V. Model School. His performance on the project was quite satisfactory

SIGN

ACKNOWLEDGEMENT

I would like to sincerely thank my chemistry teacher Mrs. Vibha mam for supporting me throughout the practical classes and helping me for completing this project without whose help I wouldn’t have come so far, also I would like to thank the lab assistant for also being there in the lab during experiments and helping me get acquainted with all the apparatus.

INDEX

IntroductionApparatus ChemicalsTheoryAnalysisProcedureTable 1

1,2,5 paisaTable 2

Rs 1, 2, 5 coinsConclusion

PrecautionBibliography

INTRODUCTION

Man was always been curious to know the nature of things around him. He has been continuously exploiting his surroundings in all possible ways to penetrate deep into the origin of all the things. He began with understanding the physical and chemical composition of various substances. These experiments led him to understand the nature in better way.

Everybody in his or her daily life come across various types of coins. When we sell something we get coins and when we buy something we give coins.

Leonardo-do Vinci once said “Experiments are the interpreter of nature” Experiments are the surest way to the confirmation of all processes. Here is an endeavour to satisfy that curious urge of enquiry. This project tries to analyse the various metals present in the coins used in many parts of India, which were used in ancient times as well as the once which are used in present times.

APPARATUS

Test tubesTest tube standTest tube holderBunsen burnerBeakersPetri dishesFilter paperDroppersGlass RoadsDifferent Types Of Coins

CHEMICALS

Dilute HClConc. HNO3

Conc HClDilute HNO3

Dilute H2SO4

Potassium ChromatePbCl2

NH4NO3

K4[Fe(CN)6]Solid AlCl3

COnc NH4ClKCNSNaOHFe(CN)6

THEORYAlloy: An alloy may be defined as a homogeneous mixture of two or more metals or a metal and a non-metal. Example Brass, Bronze, Stainless Steel. There are two general types of alloy.

Inter-metallic compounds and interstitials compounds of metals with a non-metal.

Solid solution of meta and non –metals in metals.

SOME ADVANTAGES OF MAKING ALLOY ARE GIVEN BELOW.

S.No. ADVANTAGES EXAMPLES1 To increase

hardnessAlloy of iron with carbon

2. To reduce corrosion Taking stainless steel from iron

3. To reduce sensitivity

Brass, an alloy of Cu is more tenacious

4. To get better casting

Antimony, added to lead to make type metal

5. To lower melting boiling point

Soldier, an alloy of lead iron

6. To modify chemical activity

Amalgams are made for this purpose

ANALYSISThe analysis of elements in Indian coins is based upon the salt analysis scheme of the basic radicals confirmatory tests of elements involved are as follows:

We can determine the constituent of an unknown alloy by dissolving it in some simple acid or aquaregia and the solution, thus obtained can be subjected to usual qualitative analysis to determine the constituent.

LEAD (Pb 2+ ) : To test for “lead” first of all add dil. HCl to original solution and lead is precipitated as PbCl2

Pb2+ + 2Cl- PbCl2

(White)

The solution of lead chloride given a yellow precipitate of lead iodine with potassium iodide solution and of lead chromate with potassium chromate solution.

PbCl2 + 2KI PbI2 + 2KCl (Yellow ppt.)

PbCl2+K2CrO4 PbCrO4 + 2KCl (Yellow ppt.)

COPPER (Cu 2+ ) : Copper belongs to the second group and gives black ppt. of CuS when H2S is passed through original solution plus dil. HCL.

Cu + H2S CuS+ 2H+

(Black ppt.)

Black precipitate of copper sulphide dissolves in 50% HNO3 acid forming a green solution of copper nitrate.

3Cu+8HNO3 3Cu(NO3)2 + 2NO + 4H2O (Green Solution) CONFIRMATORY TEST

Cu(OH)2 + 2NH4NO3 + 2NH4OH Cu(NH3)4(NO3)2 + 4H2O

(Deep blue)Cu(NO3)2+ 2NH4OH

Cu(OH)2+2NH4NO3

(Black ppt.) If NaOH is added in excess: Cu(OH)2 + 2NH4NO3 + 2NH4OH Cu(NH3)4(NO3)2 + 4H2O (Deep blue)

2CuSO4+K4(FeCN6)+2K2SO4

ALUMINIUM (Al 3+ ) : Aluminium gives white ppt. of Al(OH)3 in the IIIrd group. When NH4 along with NH4CL is added

3Al+3NH4OH Al(OH)3+3NH4

(White gelatinous ppt.)

Filter and dissolve the ppt. in a little dil. HCL and a drop of blue litmus paper solution and add to it dil.NH4OH drop wise. A blue lake is formed. In case, Al (OH)3 absorbs all the colouring matter of the litmus forming a complex compound called blue lake.

IRON(Fe 3+ ) : Iron gives reddish brown ppt. in the IIIrd group test. Fe3+ + NH4OH Fe(OH)3+3NH4

(Brown ppt.)

The ppt. of Fe(OH)3is soluble in dil. HCL giving FeCL3

CONFIRMATORY TEST

4FeCl3 + 3K4[Fe(CN)6] Fe4[Fe(CN)6] + 12KCl (Ferric Frrrocyanide)

4 FeCL3 + 6KCNS K3Fe(CNS)6 + 3KCl.

(Pot.Sulphocyanide) (Pot.Feric Sulphosyanide)

ZINC(Zn 2+ ) : If Zn2+ is present then on passing H2S through the IIIrd group white precipitate is formed.

Zn2+ + H2S ZnS + 2H+

(White ppt.)

Dissolve the ppt. in dil. HCL and boil of H2S

ZnS + 2HCL ZnCL2 + H2S (i)ZnCL2 + 2NaOH Zn(OH)2 + 2NaCl (White ppt.)

If NaOH is added in excess:

Zn(OH)2+2NaOH Zn(ONa)2+2H2O (Sod. Zincate)

(ii) 2ZnCL2 + K4Fe(CN)6 Zn2Fe(CN6)+4KCl (Zinc. Ferro cyanide)MAGNESIUM (Mg 2+ ) : To the solution add NH4OH and (NH4)3 PO4

i.e. Ammonium phosphate in excess. White ppt. of Mg NH4CL is formed.

Mg(NO3)2 + Na2HPO4 + NH4OH Mg NH4PO4+2NaNO3+H2O

PROCEDURE

PREPARATION OF AQUAREGIA: Took a clear beaker and put three test tubes of conc. HCL in it. To this add one test tube of concHNO3 stir it. Thus, form mixture of aquaregia.

TAKE THE SMALL BEAKERS: And paste a white blank slip on these. Put equal amount of aquaregia in all the beakers and label them according to the coins to be put into them.

CLEAN THE COINS: So that no dust is left on them and dry them. Put them in beakers label for them. Place three beakers in some safe place and remain them for two to three days.

After two days, COINS WERE DISSOLVED and there was solution in the beakers. Add half beaker of water in each solution.

Detect the basic radicals step by step in each coin. Tables are given below showing the observations and result of qualitative analysis..

TABLE 1

For coins of 1, 2, 5 paisa..

S.No

EXPERIMENT OBSERVATION

INFERENCE

1. Observe the colour of the coin

Silvery white

Al3+, Zn may be present

2. Dissolve them in aquaregia

Gas evolved NO2 may be present.

3. To the O.S. add dil. HCL

No ppt of HCL

Group 1st is absent.

4. To the above sol pass H2S

No precipitate

Group 2nd is absent

5. To the OS add NH4Cl and boil, and then add NH4OH in excess.

White precipitate formed.

Group 3rd may be present.

6.

i)

Confirmatory test:Dissolve the above ppt. in HCl. To this add blue litmus and then add NH4OH drop wise.

Blue lake. Al3+ confirmed.

7. To a part of O.S. add KCNS.

No colour. Fe3+ absent.

8. To the 3rd group filtrate added H2S. If ppt forms pass H2S through the whole solution.

Black ppt formed.

Group 4 present.

9. Dissolve the black Yellow Ni2+ may be

ppt in aquaregia. Evaporate to dryness.

residue. present.

i)

ii)

Confirmatory Test:Yellow residue+ distilled water.divide in two parts.Part 1+NH4OH+ a few drops of dimethylglyoxime(DMG)Part 2+NaOH solution water and boil

Green colour solution

Bright Rose red ppt formed

Black ppt forms

Ni2+

confirmed

Ni2+

confirmed

Reduce the group 4 filtrate to its 1/3rd by boiling +NH4OH take a portion and add (NH4OH)2CO3 solution+ warm and allow to stand

No ppt formed

Group 5 absent.

TABLE 2

For coins of Rs 5, Rs2 and Rs1.. S.No

EXPERIMENT OBSERVATION

INFERENCE

1. Observe the colour of the coin

Silvery white

Al3+, Zn may be present

2. Dissolve them in aquaregia

Gas evolved NO2 may be present.

3. To the O.S. add dil. HCL

No ppt. Group 1st is absent.

4. To the above solution pass H2S

Black precipitate formed

Group 2nd is present

5.

i)

ii)

Wash the ppt with water + 50% HNO3 and boil.CONFIRMATORY:Divide the solution in three parts.Part 1 + excess of NH3.Part 2 + Acetic acid + potassium Ferrocynaide

Bluish green

Blue colour

Chocolate brown ppt

Cu2+ may be present.

Cu2+ confirmed

Cu2+ confirmed

6. To the OS add NH4Cl and boil, and then add NH4OH in excess.

Reddish brown precipitate formed.

Group 3rd may be present.

6.

i)

ii)

Confirmatory test:Ppt + dil HCl dissolve and divide in 2 portionsPortion 1+ pot ferrocynaide solution

Portion 2+ pot.

Prussian blue colouration.Blood red

Fe3+

confirmed.

Fe3+

sulphocyanide solution

colouration confirmed.

8. To the 3rd group filtrate added H2S. If ppt forms pass H2S through the whole solution.

Black ppt formed.

Group 4 present.

9. Dissolve the black ppt in aquaregia. Evaporate to dryness.

Yellow residue.

Ni2+ may be present.

Confirmatory Test:Yellow residue+ distilled water. Divide in two parts.Part 1+NH4OH+ a few drops of dimethylglyoxime(DMG)Part 2+NaOH solution water and boil

Green colour solution

Bright Rose red ppt formed

Black ppt forms

Ni2+

confirmed

Ni2+

confirmed

CONCLUSION

1) The one to five paisa coins contain: Al3+, Ni2+ ions.

2) The coins of Rs 1, Rs 2, Rs 5 contain: Cu2+, Fe3+, Ni2+ ions.

PRECAUTION

i) Handle the apparatus carefully.ii) The solution of aquaregia prepared should be

handled carefully.iii) The colour of the solution made after test should

be observed carefully. iv) The chemicals should be put accurately in the test tubes.

BIBLOGRAPHY

www.google.com

www.rbi.org.in/currency/museum/c-rep.html