460 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



(2.) Ammon-Cdpriammonium Acetobromide, 

 Cu(NH3)3BrC2H302 . HA 



This compound is formed readily when cupric bromide is dissolved 

 in a mixture of alcohol and glacial acetic acid, and an excess of dry 

 ammonia gas is passed into the solution. It is essential to have the 

 solutions concentrated. For example, 2.5 grams of cupric bromide 

 were shaken with 13 cubic centimeters of glacial acetic acid and 25 

 cubic centimeters of alcohol. Upon cooling after the addition of the 

 ammonia, which raised the temperature of the solution, the desired 

 substance separated out. If when passing in the gas a black precipi- 

 tate (Cu3Br(;(NH3)io) falls after the solution has become dark purple,* 

 the supernatant liquid should be decanted before it is allowed to crys- 

 tallize. The precipitate shows the presence of an excess of cupric 

 bromide in proportion to the acetic acid. 



Ammon-cupriammonium acetobromide had already been made by 

 Richards and Shaw ; but the analyses of the compound were so un- 

 satisfactory that no account of the substance was given in their paper. 

 This unsatisfactoriness was due, not to any difficulty in preparing the 



* Richards and Sliaw, he. cit. 



