SALTS OF ZINC. 575 



ture, which disappears on cooling. Oxide of zinc combines 

 with acids and forms salts, which are colourless like those of 

 magnesia. It is precipitated as a white gelatinous hydrate, by 

 ammonia, and redissolved by an excess of that alkali. It is 

 soluble also in potash and soda, and combines with several 

 other basic oxides. Its salts, containing a strong acid in excess, 

 are not affected by sulphuretted hydrogen, but give a white 

 hydrated sulphuret with an alkaline sulphuret. By the oxida- 

 tion of zinc in air and water, without access of carbonic acid, a 

 hydrate, 3Zn O + HO, has been obtained in crystalline needles, 

 (Mitscherlich.) 



The native sulphuret of zinc, or zinc blende, Zn S ; crystal- 

 lizes in octohedrons. Its colour is variable, being sometimes 

 yellow, red, brown or black. 



Chloride of zinc, Zn Cl, is produced by the combustion of 

 zinc in chlorine, and by dissolving the metal in hydrochloric 

 acid. It is fusible at 212, volatile at a red heat, and perhaps 

 the most deliquescent of salts. 



Iodide of zinc, is formed by digesting iodine, zinc and water 

 together, and resembles the chloride. 



The neutral carbonate of zinc, forms the ore of zinc, cala- 

 mine. When precipitated by an alkaline carbonate, the salts of 

 zinc, like those of magnesia, yield the neutral carbonate in com- 

 bination with hydrated oxide, 2(ZnO, CO 2 ) +3(Zn O, HO). 

 The mineral substance, zinc bloom, is of the same composition. 

 Precipitated in the cold, the carbonate is ZnO,CO 2 + 2(ZnO,HO), 

 but is contaminated by sulphate of soda, (Mitscherlich.) 



Sulphate of zinc, White vitriol, ZnO, SO 3 + 7HO. This salt 

 is formed by the oxidation of the native sulphuret at a high 

 temperature, or by dissolving the metal in dilute sulphuric acid. 

 It crystallizes in colourless prismatic crystals, containing 7 eq. 

 of water, of which the form is a right rhombic prism. These 

 crystals are soluble in 2| times their weight of water, at the 

 usual temperature, and fuse in their water of crystallization, 

 when heated. It also crystallizes above 86, with 6 eq. of 

 water, in an oblique rhombic prism (Mitscherlich). Another 

 hydrate is formed and precipitated as a white powder, accord- 

 ing to Kuhn, containing 2 eq. of water, when a concentrated 

 solution of sulphate of zinc is mixed with oil of vitriol. The 

 sulphate of zinc forms the usual double salt with sulphate of 

 potash, ZnO, SO 3 + KO, SO 3 + 6HO. The double sulphate of 



p P 



