ACETATES AND THEIR MANUFACTURE. 279 







Chromous acetate, (C 2 H 3 O 2 ) 2 Cr -f H 2 O, is prepared by mixing a 

 solution of chromous chloride with sodium acetate. The salt- 

 separates out in small, lustrous red crystals which are sparingly 

 soluble in water and alcohol and quickly oxidize to a greater 

 degree on exposure to the air, the succeeding salt being formed. 



Chromic acetate. A neutral salt is known and there are very 

 likely several basic ones. The solution of the neutral salt, which 

 is obtained by dissolving chromic hydrate in heated acetic acid, 

 forms a red fluid, green in a reflected and red in a transmitted 

 light. It is not decomposed by boiling, but by ammonia. The 

 precipitate, however, redissolves, on adding ammonia in excess, to 

 a violet-red fluid because the hydrate is soluble in ammonium 

 acetate. Hence, a solution of the salt acidulated with acetic acid 

 is not precipitated by ammonia. 



There are also known crystallized combinations of this salt 

 with chromic chloride and sulphate and nitrate of chromium. 



If the solution of the neutral salt is for some time digested 

 with chromic hydrate, it acquires a darker color, the acid re-action 

 disappears, and on evaporating a green powder soluble in water 

 remains behind. Ordway has described a purple basic salt. 



Nickel acetate forms small green crystals soluble in water, but 

 not in alcohol. 



Cobalt acetate forms small red crystals, the concentrated solution 

 of which turns blue on heating but again red on cooling, and can, 

 therefore, be used as sympathetic ink. 



Zinc acetate, Fn(C 2 H 3 O 2 ) 2 . This salt may be prepared by 

 dissolving metallic zinc, zinc oxide or zinc carbonate in acetic 

 acid, or by the decomposition of zinc sulphate by acetates of lime 

 or lead similar to the acetate of manganese. The acetate is 

 in the first three instances simply obtained by evaporation, and 

 in the latter, after agitating the mixture, filtering and evaporating 

 the filtrate. The salt crystallizes in flexible, opalescent, six-sided 

 tables which effloresce slightly in the air. Technically the best 

 receipt is to dissolve 4 parts of the sulphate of zinc and 7 J parts 

 of acetate of lead each in 3 parts of hot water, mixing the solutions, 

 agitating, and after the sulphate of lead has deposited, drawing 

 the clear liquid off to crystallize. 



