Chlorides

Chlorides are the salts of hydrochloric acid, HCl, and may be represented by the formula MC1 where M is a monobasic element. They are generally formed by dissolving the metal or its oxide in the acid. Many may be prepared by direct union of the metal and the gas. Thus antimony takes fire if sifted into chlorine gas forming the chloride SbCl₃. With the exception of lead, silver, and mercurous chlorides (PbCl₂, AgCl and HgCl) they are all soluble in water. Many of them are very important commercially or chemically. Ordinary common salt consists of sodium chloride, NaCl. Calcium chloride, CaCl₂, is largely employed for drying gases, and barium chloride, BaCl₂, is an invaluable chemical reagent. Zinc chloride, ZnCl₂, is used as a desiccator and antiseptic, and its solution forms Burnett's disinfecting liquid. Chloride of gold, AuCl₃, is largely used in photography, and platinum tetrachloride, PtCl₄, in chemical analysis. The two chlorides of mercury, HgCl and HgCl₂, known respectively as calomel and corrosive sublimate, are also largely employed in medicine. Ammonium chloride, NH₄Cl, forms the sal-ammoniac of commerce. The compounds of chlorine with non-metals or with organic radicals are also called chlorides, as nitrogen chloride, NCl₃, ethyl chloride, C₂H₅C1. Most of these are of great theoretical interest, and many of industrial importance.