The chemical compound potassium chloride (KCl) is a metal halide salt composed of potassium and chloride. It is odorless and has a white or colorless vitreous crystal appearance.The solid dissolves readily in water and its solutions have a salt-like taste.KCl is used in medicine, scientific applications, food processing, and used to cause cardiac arrest as the third drug in the three drug cocktail for executions by lethal injection.he solid dissolves readily in water and its solutions have a salt-like taste. KCl is used in medicine, scientific applications, food processing, and used to cause cardiac arrest as the third drug in the three drug cocktail for executions by lethal injection.