Development of Karl Fischer Reagents
Development of Karl Fischer Reagents
Development of Karl Fischer Reagents
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III-1. Industrial Products<br />
(2) Moisture vaporization - Coulometric titration<br />
<strong>Reagents</strong> used: Aquamicron AX (or AS) 150ml<br />
Aquamicron CXU 10ml<br />
156<br />
Substance<br />
Cuprous oxide<br />
"<br />
Titanium oxide<br />
Yellow pigment<br />
Red pigment<br />
Barium carbonate<br />
12. Paints<br />
Key Points<br />
Heating Temperature<br />
( � C)<br />
230<br />
700<br />
200<br />
230<br />
200<br />
500<br />
Sample Quantity<br />
(g)<br />
0.3651<br />
0.1497<br />
1.0378<br />
0.1949<br />
0.0415<br />
3.1009<br />
Measurement Value<br />
(µg)<br />
2959<br />
1953<br />
3631<br />
2028<br />
2370<br />
4.30<br />
Moisture Content<br />
(%)<br />
0.810<br />
1.300<br />
0.350<br />
1.040<br />
5.710<br />
0.130<br />
Moisture content in paints causes bubbling, condensation and lumps in<br />
painted surfaces. Moisture measurement is, therefore, very important<br />
for quality management.<br />
Drying methods cannot be used as there is a risk that other constituents<br />
will vaporize with the water. Distillation is also unsuitable because it<br />
takes too long, and because many paints include hydrophilic<br />
substances that are difficult to separate. As a result, <strong>Karl</strong> <strong>Fischer</strong><br />
titration has been chosen as the moisture measurement method for<br />
paints and it is stipulated as a Japanese industrial Standard (K5407).<br />
Paints include a variety <strong>of</strong> film-forming substances as well as various<br />
other ingredients such as enamels with pigments and varnishes, some<br />
<strong>of</strong> which may react with <strong>Karl</strong> <strong>Fischer</strong> reagent.<br />
The possibility that some <strong>of</strong> these substances will cause an interference<br />
reaction is something that must be checked in advance.<br />
JIS K5407 (testing method for paint constituents) stipulates both<br />
volumetric and coulometric titration. The level <strong>of</strong> moisture content in<br />
paints is generally within the range for either method. If a product<br />
contains a number <strong>of</strong> substances that will not dissolve in solvents,<br />
volumetric titration should be used in preference to coulometric titration.<br />
For volumetric titration, the sample must be dissolved or dispersed in a<br />
suitable solvent in preparation for <strong>Karl</strong> <strong>Fischer</strong> titration. A ketone-type<br />
dehydrated solvent is excellent for samples that contain ketones. If a<br />
sample contains other substances that cause interference reactions,<br />
<strong>Karl</strong> <strong>Fischer</strong> titration should be used in combination with moisture<br />
vaporization. Either volumetric or coulometric titration can be used in
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