Development of Karl Fischer Reagents

III-1. Industrial Products
136
Substance
Sample quantity
(g)
Measurement value
(µg)
Moisture content
(%)
IBP* 1.0260 2210 0.215
*:O,O-Diisopropyl-S-benzylthiophosphate
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS) 150ml
Aquamicron CXU 10ml
Substance
TPN (Daconil)
Zineb (Diefar)
Namekat
Captan
Bryeslin powder
Heating Temperature
( � C)
100
110
110
110
150
Sample Quantity
(g)
0.4867
0.1021
0.1314
0.0679
0.1109
Measurement Value
(µg)
0241
1459
6606
1914
4822
Captan: N-Trichloromethylthio-4-cyclohexene-1,2-dicarboximide
TPN: Tetrachloroisophthalonitrile
Zineb: Zinc ethylenebisdithiocarbamate
3. Glass/Ceramics
Key Points
Moisture Content
(%)
495ppm
1.43
5.03
2.82
4.35
Because glass, ceramics and similar substances do not dissolve in
organic solvents, both volumetric titration and coulometric titration are
used in combination with moisture vaporization.
The heating temperature and other conditions for moisture vaporization
must be determined with reference to the type of sample. Particular
care is required with glass as it will melt at certain temperatures and
adhere to the sample boat used in the moisture vaporization method.
Up to about 600 � C, adhesion can be stopped if the boat is covered with
aluminum foil.
Direct titration is not possible with cement. The moisture content of
cement is chemically bonded, while the oxides in cement cause
interference by reacting with Karl Fischer reagent to produce water. The
usual method is to carry out moisture vaporization at 800-1,000 � C,
followed by Karl Fischer titration.