Development of Karl Fischer Reagents
Development of Karl Fischer Reagents
Development of Karl Fischer Reagents
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II-1 Organic Compounds<br />
(2) Coulometric titration<br />
<strong>Reagents</strong> used: Aquamicron AX (or AS) 100ml<br />
Aquamicron CXU 5ml<br />
Acetonitrile<br />
Acrylonitrile<br />
102<br />
Substance<br />
15. Hydrazines<br />
Key Points<br />
Sample quantity<br />
(g)<br />
0.7691<br />
0.0800<br />
Measurement value<br />
(µg)<br />
822<br />
295<br />
Moisture Content<br />
(ppm)<br />
1070<br />
3690<br />
Iodine oxidation causes hydrazine derivatives to react with <strong>Karl</strong> <strong>Fischer</strong><br />
reagent as shown in the following formula.<br />
2C6H5NHNH2+2I2�3HI+C6H5NH2 HI+C6H5NN=N<br />
<strong>Karl</strong> <strong>Fischer</strong> titration is possible also with acidic solvents. Moisture<br />
content can be measured without this reaction if the sample is first<br />
dissolved in an excess <strong>of</strong> acetic acid (approx. 2g <strong>of</strong> sample in 25ml <strong>of</strong><br />
acetic acid).<br />
The moisture content <strong>of</strong> dinitrophenyl hydrazine and benzoyl hydrazine<br />
can also be measured accurately if the sample is dissolved in acetic<br />
acid and then titrated. Hydrazine hydrochloride reacts with iodine on a<br />
mole-for-mole basis, but hydrazine sulfate does not react with <strong>Karl</strong><br />
<strong>Fischer</strong> reagent and can be dissolved in methanol for titration.<br />
In the case <strong>of</strong> hydrazine compounds, volumetric titration is the only<br />
method that can be used. Coulometric titration is not suitable.<br />
[Examples <strong>of</strong> Measurement]<br />
(1) Volumetric titration<br />
<strong>Reagents</strong> used: <strong>Karl</strong> <strong>Fischer</strong> Reagent SS-Z (or SS)<br />
Dehydrated Solvent GEX (or MS) approx. 50ml<br />
Titrate after cooling to 15 � C or lower.<br />
Substance<br />
Dehydrated<br />
solvents<br />
Sample<br />
Quantity (g) Measurement<br />
Value (mg)<br />
Moisture<br />
Content (%)<br />
Hydrazine General-use 0.0296 0.84 2.85
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