Development of Karl Fischer Reagents

[Procedures]
Chapter I: Basic Knowledge
a) Electrolyte solutions (Aquamicron AX and CXU) are introduced into the
anode and cathode chambers of an electrolysis cell (Figure 3) attached
to an automatic coulometric moisture meter (Figure 2).
b) An electrolytic current is passed through the anolyte as it is stirred in the
anode chamber. All water is removed from the electrolysis cell by
producing iodine until the end-point is reached. (It is not necessary at this
time to read the amount titrated.)
c) The sample is then introduced, and the electrolysis process is started
again.Coulometric titration is continued until the end-point is reached.
The end-point is detected electrically by means of a detection circuit built
into the titration system.
d) Moisture content is automatically calculated from the amount of electricity
required for electrolysis in the automatic coulometric moisture meter. The
amount of water is expressed in ug units.
Moisture content (ppm) =
Measurement
system
Titration bath Electrolysis
cell
Sample
injection port
Detection
electrode
Anolyte
Rotor
Anode
chamber
Cathode
chamber
Anode
Magnetic stirrer
Measured value (ug)
Quantity of sample (g)
Catholyte
Cathode
Diaphragm
Power source
for electrolysis
current
Control unit
Drying tube
Figure 2: Automatic Coulometric Moisture Meter
Detection
unit
Display
Recording
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