Introduction to Laboratory Equipment By Douglas Rittmann, Ph.D., P.E. Water

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

3. Conductivity Meter

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

5. Spectrometer Analysis Lambert & Beer�s Law � Light adsorption varies with concentration % light transmission vs. concentration is linear on semi-log paper. T = I/Io = 10-kl (straight line on semi-log paper)

6. Digital Spectrometer First, check that the instrument is turned on. You will hear the fan and see light coming out of the right side of the instrument. A digital spectrometer measures the amount of visible light absorbed by a colored solution. This can be read as Absorbance or % Transmittance. Next press the A/T/C button to select Absorbance mode. The current mode appears on the display.

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

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

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

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

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

12. Digital Spectrometer Remove the blank and insert a dry sample cuvet.

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

14. Quantitative Chemistry Analytical Balance needed for: Preparation of Standard Solutions Gravimetric Analysis: Suspended Solids (fixed and organic) Sludge Solids (fixed and organic) Dissolved Solids (fixed and organic)

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

16. Analytical Balance Place creased, small weighing paper on the balance pan. Close the sliding glass doors. Wait for the green dot on the left to go out. This is the stability indicator light, indicating that the weight is stable.

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

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

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

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

21. PH Measurement pH test measures the hydrogen ion concentration pH = - log [H+] or pH = log 1/[H+] Scale 0 to 14, <7.0= acidic, >7.0=alkaline, 7.0=neutral Importance in Water: Coagulation, Disinfection, Water Softening, Corrosion Control Importance in Wastewater: Biological Processes, Chemical processes, oxidation of cyanide ion.

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

23. PH Meter Press the Setup button twice, then press the Enter button to clear the existing standardization

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

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

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

27. PH Meter Remove the solution from the pH 4 buffer and rinse the electrode

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

29. Buret Buret A buret is used to deliver solution in precisely-measured, variable volumes. Burets are used primarily for titration, to deliver one reactant until the precise end point of the reaction is reached. Using a Buret To fill a buret, close the stopcock at the bottom and use a funnel. You may need to lift up on the funnel slightly, to allow the solution to flow in freely. 

30. Buret You can also fill a buret using a disposable transfer pipet. This works better than a funnel for the small, 10 mL burets. Be sure the transfer pipet is dry or conditioned with the titrant, so the concentration of solution will not be changed. Before titrating, condition the buret with titrant solution and check that the buret is flowing freely. To condition a piece of glassware, rinse it so that all surfaces are coated with solution, then drain. Conditioning two or three times will insure that the concentration of titrant is not changed by a stray drop of water.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

45. Questions?