280 VINEGAR, CIDER, AND FRUIT-WINES. 



Acetates of copper. Cuprous acetate, Cu 2 (C 2 H 3 O 2 ) 2 . This salt 

 is produced by subjecting crystallized verdigris to dry distillation. 

 It is a white substance crystallizing in fine needles, which are 

 decomposed by water into yellow cuprous hydrate and cupric 

 acetate. 



With cupric oxide acetic acid forms a normal and several basic 

 salts. 



Neutral cupric acetate ; crystallized verdigris, Cu(C 2 H 3 O 2 ) 2 . The 

 normal cupric acetate may be prepared by dissolving pure cupric 

 oxide or cupric hydrate in pure acetic acid or by employing, instead 

 of the pure oxide, copper scales whose content of metallic copper 

 and of cuprous oxide is converted into cupric oxide by moistening 

 with nitric acid and gentle glowing ; the cupric oxide thus obtained 

 is washed to remove foreign substances. The conversion of the 

 cuprous oxide into cupric oxide is especially essential when the 

 acetic acid is not entirely free from hydrochloric acid, as other- 

 wise cuprous chloride is formed which dissolves with difficulty. 



If copper scales cannot be obtained, hydrated basic carbonate 

 of copper can be prepared by precipitating sulphate of copper 

 with soda, and, after washing and pressing, dissolving in acetic 

 acid. Sulphate of soda remains dissolved in the water, and this 

 solution can eventually be utilized for the conversion of crude 

 calcium acetate into sodium salt. Instead of soda, milk of lime 

 can also be used for the decomposition of the sulphate of copper : 

 a mixture of calcium sulphate and cupric hydrate is precipitated. 

 By adding acetic acid the latter is redissolved while the calcium 

 sulphate remains suspended. When the latter has settled the 

 solution is drawn off and evaporated. The calcium sulphate is 

 repeatedly washed with small portions of water, and the wash- 

 waters used for dissolving fresh quantities of sulphate of copper. 



In case the sulphate of copper contains iron the latter is re- 

 moved by digesting the solution for several days with basic car- 

 bonate of copper. The presence of iron is recognized by the sul- 

 phate not dissolving entirely in ammonia in excess, but leaving 

 behind a red-brown residue (ferric hydrate). 



The neutral acetate can also be prepared by dissolving the 

 basic salt, verdigris (described below), in acetic acid. The solu- 



