Analytical method for coulometric determination of water in chemicals, formulations, composites, developed by Karl Fischer (1901-1958) German chemist. Iodine formed on the Platinum electrode reacts with water and sulfur dioxide. Each iodine molecule reacts with one water molecule. The reaction has high accuracy and selectivity, useful for determination of trace amounts of water as well as of materials with high water content. No need of special sample preparation. The method has good reproducibility and suitable for automatization.