SALTS OF ZINC. 



zinc and soda contains 4 atoms of water, ZnO, SO 3 -f NaO, SO 3 + 

 4HO. It is formed by a singular decomposition (page 190). 

 When a solution of the sulphate is mixed with a quantity of 

 alkali less than sufficient for complete precipitation, a subsulphate 

 of zinc precipitates, which according to the analyses of several 

 chemists, contains 4 eq. of oxide of zinc to I eq. of sulphuric acid, 

 besides water. A concentrated solution of sulphate of zinc dis- 

 solves the preceding subsalt, and when saturated contains a com- 

 pound of 1 eq. of acid and 2 eq. of base, according to Schindler, 

 and does not crystallize. From this solution Schindler obtained 

 the former insoluble subsalt with two different proportions of 

 water, in long crystalline needles, containing 10HO, by the 

 spontaneous evaporation of the solution, and in brilliant crystal- 

 line plates, containing 2HO, which were deposited on boiling 

 the solution. He also obtained another subsalt, by diluting the 

 same solution with a large quantity of water, as a light bulky 

 precipitate, which contained 1 eq. of acid, 8 eq. of oxide of zinc, 

 and 2 eq. of water. The insoluble matter which precipitates 

 when dry sulphate of zinc combined with 1 eq. of ammonia 

 (page 412), is thrown into water, is considered, by Dr. Kane, a 

 third subsulphate of zinc, containing 1 eq. of acid, 6 eq. of oxide 

 of zinc, and 10 eq. of water. All these subsulphates afford 

 neutral sulphate of zinc to water, after being heated to redness, 

 so that whatever their constitution may be, when hydrated, it is 

 certainly different from what it is in their anhydrous condition. 



Nitrate of zinc, ZnO, NO 5 + 6HO, is very soluble in water, 

 and moderately deliquescent. 



Phosphate of zinc, ZnO 2 . HO, PO 5 + 2HO, is obtained 

 in minute silvery plates, which are nearly insoluble, on mixing 

 dilute solutions of phosphate of soda and sulphate of zinc. 



Silicate of zinc is found as a crystalline mineral, which 

 has received the name of the electrical oxide of zinc, because it 

 acquires, like the tourmalin, a high degree of electrical polarity 

 when heated. It contains water, and may be represented by 

 the formula 2 (3ZnO, SiO 3 ) -f 3HO. 



The most important alloys of zinc are those with copper, 

 which form the varieties of brass. Zinc also combines readily 

 with iron, and is contaminated by that metal, when fused in an 

 iron crucible. 



