24
General Conductivity Measurement Precautions
After selecting the proper cell, observe the following precautions to ensure accurate, repeatable
results:
1.
The cell must be clean before making any measurements. When working with substances
having low conductivity, extraordinary cleanliness may be required.
2.
Soak cells that have been stored dry in deionized water before use.
3.
Immerse the cell in the solution deep enough to submerge the vent hole.
4.
The electrode chamber should be free of trapped air.
5.
The cell should be at least ¼ inch away from any other object, including the walls or
bottom of the solution container.
6.
Stirring may be necessary for highest accuracy measurements, especially in low-
conductivity solutions and to achieve good thermal equilibration.
7.
If possible, isolate from ground potential the measurement container.
8.
Electrical fields and stray currents caused by stirrer motors, heaters, etc., can interfere
with measurements. The user should determine the effects of these and make the
necessary corrections, either by shielding or by disconnecting those units that cause
trouble.
9.
Always handle the cell carefully.
10.
Always rinse the cell carefully before transferring it from one solution to another.
11.
Never store a dirty or contaminated cell.
12.
The cells should not be submerged in aqua regia or any solution which might etch or
dissolve gold.
Platinization
Platinum Black Inspection
The electrodes of YSI 3200 and 3400 Series conductivity cells are coated with platinum black
during manufacturing. This coating is extremely important to cell operation, especially in
solutions of high conductivity.
The cell should be inspected periodically. If the coating appears to be thin or if it is flaking off,
the electrodes should be cleaned and replatinized. Properly maintained conductivity cells will
perform for years without replatinizing.
Replatinizing
The 3100 can be used to replatinize a cell that utilizes electrodes coated with platinum. See
section 5.2 Platinization. You will need a 2-oz bottle of platinizing solution (YSI 3140).
Temperature Correction
By convention, the conductivity of a solution is the conductivity it exhibits at 25
°
C. The
conductivity of electrolytic solutions varies with temperature, concentration, and composition.
The amount that the conductivity changes with temperature is expressed as a percent
