ASTM E203 test method for water using volumetric Karl Fischer titration
8. Drying of Solvents
8.1 If it is necessary to prepare dry solvents in the laboratory, the following three methods can be used:
8.1.1 Azeotropic Distillation Using Benzene, to reduce the moisture to 0.05 %. Add 1 volume of benzene to 19 volumes of pyridine, ethylene glycol monomethyl ether, or mixtures thereof, and distill. Discard the first 5 % and use the dry residual 95 %.
8.1.2 Molecular Sieves - Solvents other than methanol may be dried to a moisture content of 0.05 % by passing upward through a molecular sieve25 column, using 1 part molecular sieve per 10 parts of solvent.
9. End Point Detection
9.1 There are many commercial titration assemblies on the market that are specifically designed for performing volumetric type KF titrations. All that is required of these units is pressing a "start titration" or "start" key on the instrument keyboard just prior to or after the sample has been added to the titration cell. End point detection is automatic and the amount of water in the sample is calculated once the operator enters the sample weight into the instrument's memory. The method for color end point detection is given in Appendix X1.
