Hydranal, Coulometric Titration Reagents, Honeywell

HYDRANAL-Coulomat
Coulometric Karl Fischer titrations normally require two reagent solutions: an anolyte (the solution in the anodic compartment) and a catholyte (the solution in the cathodic compartment). Hydranal-Coulomat A-type or E-type reagents are used as anolytes. The anolytes contain iodide and a sulfur dioxide/imidazole buffer in suitable solvents. Hydranal-Coulomat CG reagents are used as catholytes.

Coulometric reagents based on different solvent compositions serve to support the broad variety of samples analyzed, i.e. Hydranal-Coulomat Oil contains methanol, xylene and chloroform for titration in oils or methanol-free Hydranal-Coulomat AK for titration of ketones. Furthermore, some working techniques are supported by special reagents i.e. the use of Karl Fischer oven by Hydranal-Coulomat AG-Oven or the use of a cell without diaphragm by Hydranal-Coulomat AD.

Coulometric Cells
There are two different types of coulometric cells: those with and those without a diaphragm. The diaphragm separates the anode chamber from the cathode chamber. Oxidation of I? to I² occurs at the anode, whereas the reduction of protons to H² occurs at the cathode. For cells without a diaphragm the anodic and cathodic compartments are not separated and only one reagent, the anolyte, is needed. Though the latter coulometric cell may seem more convenient to use, the cell with diaphragm achieves the highest accuracy (down to a trace range of water).