Zirconium Chloride, ZrCl₄

Zirconium Chloride, ZrCl₄, is formed in a variety of ways, which are characteristic of the manner of formation of non-metallic rather than metallic chlorides. Thus it is produced (i) by the action of chlorine on a red-hot mixture of zircon or zirconia and charcoal; in the former case zirconium tetrachloride is mixed with silicon tetrachloride derived from the silica of the mineral; (ii) by the action of chlorine or hydrogen- chloride gas on the heated metal, when the chloride is obtained as a white, crystalline sublimate; (iii) by the action of chlorine on the carbide, ZrC, at 300° C.; (iv) by heating the oxide with phosphorus pentachloride in a sealed tube at 190°; (v) by heating the oxychloride, ZrOCl₂, to 110° C. in a stream of hydrogen chloride. According to Lely and Hamburger, however, zirconium chloride is best prepared by the action of chlorine and carbon tetrachloride on the oxide at 800° C.; and Bourion has found that the pure chloride is rapidly obtained by passing the vapour of sulphur monochloride over heated thoria.

Zirconium chloride is a white, crystalline solid which fumes in moist air and reacts vigorously with water, forming the oxychloride ZrOCl₂ which remains in solution. Zirconium chloride forms no crystallohydrate with water, but sublimes when heated, yielding a vapour whose density at 440° C. is 8.15 (air = 1) or 117.4 (H = 1) (theory for ZrCl₄ requires 116.2); it may apparently be recrystallised from hydrochloric acid, but the product probably contains some oxychloride.