Working principle of coulometric moisture analyzer
The working principle of coulometric moisture analyzer:
The Karl Fischer Coulometric method is an electrochemical method for measuring moisture. Its principle is that when the Karl Fischer reagent in the instrument's electrolytic cell reaches equilibrium, a sample containing water is injected. Water participates in the redox reaction of iodine and sulfur dioxide. Next, pyridine hydroiodide and pyridine methyl sulfate are generated, and the consumed iodine is produced by electrolysis at the anode, so that the oxidation-reduction reaction continues until all the water is consumed.
According to Faraday's law of electrolysis, the iodine produced by electrolysis is proportional to the amount of electricity consumed during electrolysis. The reaction is as follows:
H2O + I2 + SO2 + 3C5H5N → 2C5H5N · HI + C5H5N · SO3 C5H5N · SO3 + CH3OH → C5H5N · HSO4CH3
In the electrolysis process, the electrode reaction is as follows: anode: 2Iï¼-2e → I2 cathode: I2 + 2e → 2I-2H ++ 2e → H2 ↑ From the above reaction, we can see that 1 mole of iodine oxidizes 1 mole of sulfur dioxide , Requires 1 mole of water. Therefore, it is the equivalent reaction of 1 mole of iodine and 1 mole of water, that is, the amount of electricity for electrolytic iodine is equivalent to the amount of electricity for electrolyzed water. The electrolysis of 1 mole of iodine requires 2 * 96493 coulombs of electricity, and the electrolysis of 1 millimole of water requires 96493 millicoulons of electricity. The moisture content in the sample is calculated according to formula (1): where: W-moisture content in the sample, μg; Q-electrolysis capacity, mC; 18-water molecular weight.
Series of related products: volumetric moisture analyzer, Karl Fischer moisture analyzer, coulometric moisture analyzer, halogen moisture analyzer
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