Introduction to Laboratory Equipment By Douglas Rittmann, Ph.D., P.E. Water/Wastewater Consultant At...

Introduction to Laboratory Equipment

By

Douglas Rittmann, Ph.D., P.E.Water/Wastewater Consultant

At

University of Texas at El PasoCE 4153

January 31, 2006

Conductivity MeterConductivity Meter

Conductivity in units of Conductivity in units of mhos/cm or Siemens/cm mhos/cm or Siemens/cm is a measure of water's is a measure of water's ability to transmit an ability to transmit an electrical current. It is a electrical current. It is a gross, indirect gross, indirect measurement of the measurement of the concentration of ions and concentration of ions and consequently can be used consequently can be used to estimate total to estimate total dissolved solids (TDS) dissolved solids (TDS) levels. Resistivity is the levels. Resistivity is the reciprocal of conductivity.reciprocal of conductivity.


Sample Type Conductivity Range

High Pressure Boiler Water <0.1 µS/cm to 0.2 µS/cm

Demineralized Water 1 µS/cm to 80 µS/cm

Drinking Water 100 µS/cm to 1 mS/cm

Wastewater 85 µS/cm to 9 mS/cm

Surface Water 100 µS/cm to 10 mS/cm

Industrial Process Water 8 mS/cm to 130 mS/cm

Concentrated Acids and Dyes

85 mS/cm to >1000 mS/cm


Typical specifications Typical specifications are the measurement are the measurement range, accuracy and range, accuracy and the temperature of the temperature of the process media the process media being measured. being measured. Conductivity meters, Conductivity meters, dissolved solids dissolved solids meters, and resistivity meters, and resistivity meters may have meters may have some controller some controller functionality such as functionality such as set limits, regulator, set limits, regulator, P/PI/PID as well as P/PI/PID as well as control relay output. control relay output.

Spectrometer AnalysisSpectrometer Analysis

Lambert & Beer’s Law – Light Lambert & Beer’s Law – Light adsorption varies with concentrationadsorption varies with concentration

% light transmission vs. % light transmission vs. concentration is linear on semi-log concentration is linear on semi-log paper.paper.

T = I/Io = 10-kl (straight line on semi-log paper)T = I/Io = 10-kl (straight line on semi-log paper)

Digital SpectrometerDigital Spectrometer

First, check that the First, check that the instrument is turned on. instrument is turned on. You will hear the fan and You will hear the fan and see light coming out of see light coming out of the right side of the the right side of the instrument.instrument.

A digital spectrometer A digital spectrometer measures the amount of measures the amount of visible light absorbed by visible light absorbed by a colored solution. This a colored solution. This can be read as can be read as Absorbance or % Absorbance or % Transmittance.Transmittance.

Next press the A/T/C Next press the A/T/C button to select button to select Absorbance mode. The Absorbance mode. The current mode appears on current mode appears on the display. the display.


Set the Set the wavelength to wavelength to the desired the desired value using the value using the nm buttons. nm buttons. The wavelength The wavelength is displayed on is displayed on the LCD.the LCD.


Fill a cuvet Fill a cuvet with your with your blank solvent blank solvent and dry the and dry the outside of the outside of the cuvet cuvet carefully. carefully.


Insert your Insert your blank cuvet in blank cuvet in the sample the sample compartment compartment and close the and close the cover. cover.


Press 0 Press 0 ABS/100% T to ABS/100% T to set the set the absorbance of absorbance of the blank to the blank to zero. zero.


After a few After a few moments the moments the absorbance and absorbance and wavelength will wavelength will be displayed. be displayed. The absorbance The absorbance should be zero.should be zero.


Remove the Remove the blank and blank and insert a dry insert a dry sample cuvet. sample cuvet.


The The absorbance absorbance value of the value of the sample will sample will now be shown now be shown on the LCD.on the LCD.

Quantitative ChemistryQuantitative Chemistry

Analytical Balance needed for:Analytical Balance needed for:Preparation of Standard Preparation of Standard SolutionsSolutionsGravimetric Analysis:Gravimetric Analysis:Suspended Solids (fixed and Suspended Solids (fixed and organic)organic)Sludge Solids (fixed and Sludge Solids (fixed and organic)organic)Dissolved Solids (fixed and Dissolved Solids (fixed and organic) organic)

Analytical BalanceAnalytical Balance

An analytical balance An analytical balance measures masses to measures masses to within 0.0001 g. Use within 0.0001 g. Use these balances when these balances when you need this high you need this high degree of precision. degree of precision. Turn the balance on by Turn the balance on by pressing the control pressing the control bar. The display lights bar. The display lights up for several seconds, up for several seconds, then resets to 0.0000.then resets to 0.0000.


Place creased, Place creased, small weighing small weighing paper on the paper on the balance pan.balance pan.

Close the sliding Close the sliding glass doors. Wait glass doors. Wait for the green dot for the green dot on the left to go on the left to go out. This is the out. This is the stability indicator stability indicator light, indicating light, indicating that the weight is that the weight is stable. stable.


Press the control Press the control bar to cancel out bar to cancel out the weight of the the weight of the container or container or paper. The paper. The display will again display will again read 0.0000. read 0.0000.


Carefully add Carefully add the substance the substance to be weighed to be weighed up to the up to the desired mass. desired mass. Do not attempt Do not attempt to reach a to reach a particular mass particular mass exactly.exactly.


Before recording Before recording the mass, close the mass, close the glass doors the glass doors and wait until and wait until the stability the stability detector lamp detector lamp goes out. Record goes out. Record mass of solid. mass of solid.


Use the brush Use the brush provided to clean provided to clean spills in the spills in the weighing weighing chamber. Discard chamber. Discard any disposable any disposable tare containers, tare containers, weighing paper, weighing paper, or Kimwipes in or Kimwipes in the nearest the nearest wastebasket. wastebasket.

PH MeasurementPH Measurement

pH test measures the hydrogen ion pH test measures the hydrogen ion concentrationconcentration

pH = - log [HpH = - log [H++] or pH = log 1/[H] or pH = log 1/[H++]]

Scale 0 to 14, <7.0= acidic, >7.0=alkaline, Scale 0 to 14, <7.0= acidic, >7.0=alkaline, 7.0=neutral7.0=neutral

Importance in Water: Coagulation, Disinfection, Importance in Water: Coagulation, Disinfection, Water Softening, Corrosion ControlWater Softening, Corrosion Control

Importance in Wastewater: Biological Importance in Wastewater: Biological Processes, Chemical processes, oxidation of Processes, Chemical processes, oxidation of cyanide ion.cyanide ion.

PH MeterPH Meter

A Digital pH A Digital pH meter uses an meter uses an electrode to electrode to measure the pH measure the pH of a solution. of a solution. Press the mode Press the mode button to select button to select pH. pH.

PH MeterPH Meter

Press the Press the Setup button Setup button twice, then twice, then press the Enter press the Enter button to clear button to clear the existing the existing standardizatiostandardization n

PH MeterPH Meter

Press the STD Press the STD button to begin the button to begin the new calibration. new calibration. Remove the Remove the electrode from the electrode from the bottle of storage bottle of storage solution. Rinse with solution. Rinse with distilled water. distilled water.

PH MeterPH Meter

Immerse the Immerse the electrode in pH electrode in pH 4 or 7 buffer. 4 or 7 buffer. Swirl the Swirl the solution to fully solution to fully saturate the saturate the electrode with electrode with buffer. buffer.

PH MeterPH Meter

Press the STD button Press the STD button again. After the again. After the reading is stable, the reading is stable, the meter will return to meter will return to the Measure screen. the Measure screen. Press the STD button Press the STD button again to calibrate again to calibrate with a second buffer with a second buffer solutionsolution

PH MeterPH Meter

Remove the Remove the solution from solution from the pH 4 the pH 4 buffer and buffer and rinse the rinse the electrodeelectrode

PH MeterPH Meter

Immerse the Immerse the electrode in the pH electrode in the pH 10 buffer and swirl. 10 buffer and swirl. Press STD again to Press STD again to calibrate with this calibrate with this buffer. The meter buffer. The meter will display a will display a calibration calibration slope(95-102%)and slope(95-102%)and return to the return to the Measure screen. Measure screen.

Now the meter should be calibrated and ready to use for measuring the pH of any solution.

BuretBuret

BuretBuret A buret is used to deliver A buret is used to deliver solution in precisely-solution in precisely-measured, variable measured, variable volumes. Burets are used volumes. Burets are used primarily for titration, to primarily for titration, to deliver one reactant until deliver one reactant until the precise end point of the precise end point of the reaction is reached. the reaction is reached.

Using a BuretUsing a Buret To fill a buret, close the To fill a buret, close the stopcock at the bottom stopcock at the bottom and use a funnel. You may and use a funnel. You may need to lift up on the need to lift up on the funnel slightly, to allow the funnel slightly, to allow the solution to flow in freely.solution to flow in freely.

BuretBuret

You can also fill a buret using a You can also fill a buret using a disposable transfer pipet. This works disposable transfer pipet. This works better than a funnel for the small, 10 better than a funnel for the small, 10 mL burets. Be sure the transfer pipet mL burets. Be sure the transfer pipet is dry or conditioned with the titrant, is dry or conditioned with the titrant, so the concentration of solution will so the concentration of solution will not be changed.not be changed.

Before titrating, condition the buret Before titrating, condition the buret with titrant solution and check that with titrant solution and check that the buret is flowing freely. To the buret is flowing freely. To condition a piece of glassware, rinse condition a piece of glassware, rinse it so that all surfaces are coated with it so that all surfaces are coated with solution, then drain. Conditioning solution, then drain. Conditioning two or three times will insure that two or three times will insure that the concentration of titrant is not the concentration of titrant is not changed by a stray drop of water.changed by a stray drop of water.

BuretBuret

Rinse the tip of the Rinse the tip of the buret with water buret with water from a wash bottle from a wash bottle and dry it carefully. and dry it carefully. After a minute, After a minute, check for solution on check for solution on the tip to see if your the tip to see if your buret is leaking. The buret is leaking. The tip should be clean tip should be clean and dry before you and dry before you take an initial take an initial volume reading volume reading

BuretBuret

When your buret is When your buret is conditioned and filled, conditioned and filled, with no air bubbles or with no air bubbles or leaks, take an initial leaks, take an initial volume reading. A volume reading. A buret reading card with buret reading card with a black rectangle can a black rectangle can help you to take a more help you to take a more accurate reading. Read accurate reading. Read the the bottombottom of the of the meniscus. Be sure your meniscus. Be sure your eye is at the level of eye is at the level of meniscus, not above or meniscus, not above or below. Reading from an below. Reading from an angle, rather than angle, rather than straight on, results in a straight on, results in a parallax error. parallax error.

BuretBuret

Deliver solution to Deliver solution to the titration flask the titration flask by turning the by turning the stopcock. The stopcock. The solution should be solution should be delivered quickly delivered quickly until a couple of until a couple of mL from the mL from the endpoint. endpoint.

BuretBuret

The endpoint The endpoint should be should be approached approached slowly, a drop at slowly, a drop at a time. Use a a time. Use a wash bottle to wash bottle to rinse the tip of rinse the tip of the buret and the buret and the sides of the the sides of the flask. flask.

PipetPipet

A pipet is used to A pipet is used to measure small measure small amounts of amounts of solution very solution very accurately. A pipet accurately. A pipet bulb is used to bulb is used to draw solution into draw solution into the pipet.the pipet.

PipetPipet

Start by Start by squeezing the squeezing the bulb in your bulb in your preferred hand. preferred hand. Then place the Then place the bulb on the flat bulb on the flat end of the end of the pipet. pipet.

PipetPipet

Place the tip of the pipet Place the tip of the pipet in the solution and in the solution and release your grip on the release your grip on the bulb to pull solution into bulb to pull solution into the pipet. Draw solution the pipet. Draw solution in in aboveabove the mark on the the mark on the neck of the pipet. If the neck of the pipet. If the volume of the pipet is volume of the pipet is larger than the volume larger than the volume of the pipet bulb, you of the pipet bulb, you may need to remove the may need to remove the bulb from the pipet and bulb from the pipet and squeeze it and replace it squeeze it and replace it on the pipet a second on the pipet a second time, to fill the pipet time, to fill the pipet volume completely.volume completely.

PipetPipet

Quickly, remove the Quickly, remove the pipet bulb and put pipet bulb and put your index finger on your index finger on the end of the pipet. the end of the pipet. Gently release the Gently release the seal made by your seal made by your finger until the level of finger until the level of the solution meniscus the solution meniscus exactly exactly lines up with lines up with the mark on the pipet. the mark on the pipet. Practice this with Practice this with water until you are water until you are able to use the pipet able to use the pipet and bulb consistently and bulb consistently and accurately.and accurately.

Flasks & BeakersFlasks & Beakers

Erlenmeyer flasks Erlenmeyer flasks and beakers are used and beakers are used for mixing, for mixing, transporting, and transporting, and reacting, but not for reacting, but not for accurate accurate measurements. The measurements. The volumes stamped on volumes stamped on the sides are the sides are approximate and approximate and accurate to within accurate to within about 5%.about 5%.

Graduated CylindersGraduated Cylinders

Graduated cylinders Graduated cylinders are useful for are useful for measuring liquid measuring liquid volumes to within volumes to within about 1%. They are about 1%. They are for general purpose for general purpose use, but not for use, but not for quantitative analysis. quantitative analysis. If greater accuracy is If greater accuracy is needed, use a pipet needed, use a pipet or volumetric flask. or volumetric flask.

Volumetric FlaskVolumetric Flask

A volumetric flask A volumetric flask is used to make is used to make up a solution of up a solution of fixed volume very fixed volume very accurately. This accurately. This volumetric flask volumetric flask measures 500 mL measures 500 mL ± 0.2 mL. This is a ± 0.2 mL. This is a relative relative uncertainty of 4 x uncertainty of 4 x 10-4 or 400 parts 10-4 or 400 parts per million. per million.


To make up a To make up a solution, first solution, first dissolve the solid dissolve the solid material material completely, in completely, in less water than less water than required to fill required to fill the flask to the the flask to the mark. mark.


After the solid is completely After the solid is completely dissolved, very carefully fill dissolved, very carefully fill the flask to the 500 mL the flask to the 500 mL mark. Move your eye to the mark. Move your eye to the level of the mark on the neck level of the mark on the neck of the flask and line it up so of the flask and line it up so that the circle around the that the circle around the neck looks like a line, not an neck looks like a line, not an ellipse. Then add distilled ellipse. Then add distilled water a drop at a time until water a drop at a time until the bottom of the meniscus the bottom of the meniscus lines up exactly with the lines up exactly with the mark on the neck of the mark on the neck of the flask. Take care that no flask. Take care that no drops of liquid are in the drops of liquid are in the neck of the flask above the neck of the flask above the mark. mark.


After the final After the final dilution, dilution, remember to remember to mix your mix your solution solution thoroughly, by thoroughly, by inverting the inverting the flask and flask and shaking. shaking.

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Introduction to Laboratory Equipment By Douglas Rittmann, Ph.D., P.E. Water/Wastewater Consultant At...

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