On ceasing to apply heat after the chlorate has become pasty, and treating with water, the potassium chloride is dissolved, leaving the much less soluble perchlorate; the perchlorate may be purified by recrystal-lisation.

Owing to the fact that very few potassium salts are insoluble in water, it is not convenient to prepare chloric acid from the potassium salt; for this purpose it is better to use the barium salt, made from baryta-water and chlorine; a solution of this salt, when mixed with the equivalent amount of dilute sulphuric acid, yields a precipitate of barium sulphate, and chloric acid remains in solution.