Calcium Oxychloride, CaCl₂.CaO

On fusing calcium chloride in moist air it becomes basic, due to the formation of an oxysalt, CaCl₂.CaO. On prolonged heating it forms calcium oxide. When calcium chloride solution is boiled with slaked lime and the liquid filtered, white needle-shaped crystals of calcium oxychloride separate out. These are stable out of contact with air, lose part of their water of crystallisation over sulphuric acid, absorb carbon dioxide from the air, and are decomposed by water and alcohol. Various formulae have been given to the compound, for example: 3CaO.CaCl₂.15H₂O, 2CaO.CaCl₂.15H₂O, 3CaO.CaCl₂.14H₂O, and 3CaO.CaCl₂.16H₂O. The formula of the partially dehydrated salt has been given as CaCl₂.3CaO.3H₂O, and also as CaCl₂.2CaO.H₂O. Schreinemakers and his colleagues, however, have carefully studied the system, CaO: CaCl₂: H₂O, under varying conditions of temperature and concentration, and their results indicate the existence of the following compounds: at 10° and 25° C., CaCl₂.3CaO.16H₂O and CaCl₂.CaO.2H₂O; at 50° C., CaCl₂.CaO.2H₂O and CaCl₂.CaO.3H₂O; and also CaCl₂.4CaO.14H₂O.

An oxychloride of lead and calcium, 2PbO.CaCl₂.CaO, is obtained by dissolving lead oxide in boiling calcium chloride solution. By the action of a solution of calcium chloride on mercuric oxide a compound CaCl₂.2HgO.4H₂O is formed.