potassium chloride, chemical compound, KCl, a colorless or white, cubic, crystalline compound that closely resembles common salt (sodium chloride). It is soluble in water, alcohol, and alkalies. Potassium chloride occurs pure in nature as the mineral sylvite and is found combined in many minerals and in brines and ocean water. It is recovered (with other compounds) from the brine of Searles Lake in California. It is produced from sylvinite, a sodium chloride–potassium chloride mineral that is mined extensively near Carlsbad, N.Mex., and it is refined by fractional crystallization and by a flotation process. It is also recovered from lake brines in Utah and from ores in Saskatchewan, Canada. The chief use of potassium chloride is in the production of fertilizers; it is also used in chemical manufacture. For agricultural use it is often called muriate of potash; the concentration of potassium chloride in muriate of potash is expressed as a corresponding concentration of potassium oxide (K2O), i.e., the concentration of potassium oxide that there would be if the potassium were present as its oxide instead of as its chloride. Thus, muriate of potash that contains (typically) 80% or 97% KCl by weight is said to contain 50% or 60% K2O, respectively. Manure salts contain some potassium chloride.