When the Karl Fischer volumetric method is used to determine the moisture content, it is mainly based on the electrochemical reaction: I2+2eó2I- when both I2 and I- are present in the solution in the reaction cell, the reaction is carried out simultaneously at the positive and negative ends of the electrode, ie at one electrode. Upper I2 is reduced, while I- is oxidized on the other electrode, so current flows between the two electrodes. If only I- and no I2 are present in the solution, no current flows between the two electrodes. The Karl Fischer reagent contains the active ingredients such as pyridine and iodine, and is metered into the reaction tank to react with water in the solution to be tested as follows:
H2O+SO2+I2+3C5H5N→2C5H5N·HI+C5H5N·SO3
C5H5N·SO3+CH3OH→C5H5N·HSO4CH3
C5H5N·HI→C5H5N·H++I- The reaction continued, and water was continuously consumed to generate I- until the end of the reaction titration, and the water consumption was completed. At this time, the solution has a small amount of Karl Fischer reagent that has not reacted, and the simultaneous presence of I2 and I- occurs. The solution between the two platinum electrodes starts to conduct electricity, and the current indicates the end point, and the titration is stopped. The moisture content of the solution is thus calibrated by metering the volume of Karl Fischer reagent consumed (capacity).
MA-1 intelligent Karl Fischer moisture analyzer technical parameters
1. Measurement range: 10ppm-100% (H2O mass fraction)
2. Moisture content resolution: 1ppm
3. Measuring tube resolution: 0.001
4. Water titration repeatability: ≤0.005
5. Linear correlation coefficient of water titration: ≥0.999
6. Capacity error ≤ ± 0.0002
7. Relative error ≤ 0.2%
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