Development of Karl Fischer Reagents
Development of Karl Fischer Reagents
Development of Karl Fischer Reagents
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II-2. Inorganic Compounds<br />
Measuring the moisture content <strong>of</strong> sodium bicarbonate<br />
Sodium bicarbonate is used in fire extinguishers and various other applications. Even<br />
trace amounts <strong>of</strong> moisture can lead to problems during storage or use. It is difficult to<br />
measure moisture content accurately using the conventional sulfuric acid dessicator<br />
method, so the <strong>Karl</strong> <strong>Fischer</strong> titration method is used together with a moisture<br />
extraction-correction technique as described below.<br />
Approximately 100g <strong>of</strong> sample is taken in a 500ml separating funnel. To this, 130ml <strong>of</strong><br />
dehydrated methanol is added. The mixture is stirred well and then left to stand.<br />
When the sample and methanol have separated, 50ml <strong>of</strong> liquid is extracted and<br />
placed in the titration flask <strong>of</strong> a <strong>Karl</strong> <strong>Fischer</strong> titration system, and titrated. The small<br />
quantity <strong>of</strong> sample dissolved in the extracted liquid is titrated by neutralization<br />
titration, and the moisture content is determined by correcting the <strong>Karl</strong> <strong>Fischer</strong><br />
titration result.<br />
Reference:<br />
N.G. Leavitt, C.B. Robert: Anal.Chem., 26,1367 (1954).<br />
124<br />
Substance<br />
Calcium carbonate<br />
Calcium carbonate<br />
Dehydrated<br />
solvent<br />
General-use<br />
Oil-type<br />
Sample<br />
quantity (g)<br />
1.0272<br />
1.0053<br />
Measurement<br />
value (mg)<br />
1.86<br />
1.63<br />
Moisture<br />
content (%)<br />
0.181<br />
0.162<br />
Note:The end point was more stable with an oil-type dehydrated<br />
solvent.<br />
(2) Moisture vaporization - Coulometric titration<br />
<strong>Reagents</strong> used: Aquamicron AX (or AS) 150ml<br />
Aquamicron CXU 10ml<br />
Substance<br />
Calcium carbonate<br />
"<br />
Potassium carbonate<br />
Sodium carbonate<br />
Barium carbonate<br />
"<br />
Basic magnesium carbonate<br />
Manganese carbonate<br />
"<br />
Heating<br />
temperature( � C)<br />
100<br />
600<br />
200<br />
180<br />
300<br />
700<br />
250<br />
110<br />
600<br />
Sample<br />
quantity (g)<br />
0.1223<br />
0.0975<br />
0.6278<br />
0.2004<br />
0.6761<br />
0.8437<br />
0.0249<br />
0.0334<br />
0.0466<br />
Measurement<br />
value (µg)<br />
623<br />
1554<br />
1712<br />
4099<br />
805<br />
1103<br />
3605<br />
1723<br />
3699<br />
Moisture<br />
content (%)<br />
0.509<br />
1.58<br />
0.273<br />
2.05<br />
0.119<br />
0.131<br />
14.5<br />
5.16<br />
7.94
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