Development of Karl Fischer Reagents

II-2. Inorganic Compounds
Test Examples
118
Gas flow rate
(l/min.)
0.3
0.4
0.5
0.6
0.7
0.8
Volume
(l)
20
20
20
20
20
20
Measurement value
(mg)
0.44
0.43
0.45
0.40
0.38
0.33
Moisture content
(ppm)
12.6
12.4
12.8
11.5
10.4
09.4
Note:Karl Fischer Reagent SS with a titer of 0.35mg/ml was used.
(At present there is no reagent with this titer.)
3. Hydroxides
Key Points
Metallic hydroxides generally react with the iodine in Karl Fischer
reagent in accordance with the following formula. In particular, alkaline
metal and alkaline earth hydroxides (strong basicity) react quantitatively
and rapidly.
M(OH)2+2HI � MI2+H2O
For example, lithium hydroxide, sodium hydroxide, potassium hydroxide
and barium hydroxide all produce water and react immediately with
Karl Fischer reagent. For this reason, direct titration cannot be used.
Moisture content is measured using the moisture vaporization method.
[Examples of Measurement]
(1) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS) 150ml
Aquamicron CXU 10ml