PURPOSE: To easily prepare a reagent of high factor by constituting iodine, pyridine, sulfur dioxide and alkylene carbonate.

CONSTITUTION: A Karl Fisher reagent is constituted with iodine, pyridine, sulfur dioxide and alkylene carbonate which is expressed in a general formula. The representative composition of this reagent is 2W4mol of sulfur dioxide , and 8W12mol of pyridine per 1mol of iodine. A Karl Fisher reagent is prepared by blending iodine, sulfur dioxide, and pyridine in the aforementioned ratio with alkylene carbonate and making it into a solution.