Instruction Manual
Lead Electrode
7
Direct Measurement of Lead (using an ion meter)
1.
By serial dilution of the 0.1M or l,000 ppm lead standard, prepare two lead standards
whose concentration is near the expected sample concentration. Measure out 50 ml of each
standard into individual 150 ml beakers. Add 50 ml of methanol-formaldehyde solution
and 2 ml of ISA to each beaker.
2.
Place the more dilute solution on the magnetic stirrer and begin stirring at a constant rate.
Assure that the meter is in the concentration mode.
3.
Lower the electrode tips into the solution.
4.
Adjust the meter to the concentration of the lead standard and fix the value in the memory
according to the meter manufacturer's instructions after stabilization of the reading.
5.
Rinse the electrodes with distilled water and blot dry.
6.
Place the more concentrated solution on the magnetic stirrer and begin stirring at a
constant rate.
7.
Lower the electrode tips into the solution.
8.
Adjust the meter to the concentration of the lead standard and fix the value in the memory
according to the manufacturer's instructions after stabilization of the reading.
9.
Place 50 ml of the sample, 50 ml of methanol-formaldehyde solution, and 2 ml of ISA into
a 150 ml beaker. Place the beaker on the magnetic stirrer and begin stirring at a constant
rate.
10.
After rinsing the electrodes, blot dry, and lower the electrode tips into the solution. After
stabilization, read the concentration directly from the meter display.
11. The calibration should be checked every two hours. Assuming no change in ambient
temperature, immerse the electrode tips in the more dilute standard. After the reading has
stabilized, compare it to the original reading recorded in Step 4 above. A reading differing
by more than 0.5 units or a change in ambient temperature will necessitate repetition of
Steps 2-8 (2-9) above. The meter should be re-calibrated daily.