248 PROCEEDINGS OF THE AMERICAN ACADEMY 



1. Cupriammonium Acetobromide, 

 Cu(NH 3 ) 2 BrC 2 H 3 2 . 



This compound is formed with great ease whenever cupric bromide 

 is treated with alcohol and saturated ammonia water, and the mixture 

 is nearly neutralized with strong acetic acid. For example, tive grams 

 of cupric bromide were shaken with ten cubic centimeters of alcohol 

 and the like volume of saturated ammonia water, until all of the copper 

 was converted into cupriammonium bromide. The bright blue pre- 

 cipitate was then immediately dissolved in sixty or seventy cubic 

 centimeters additional of alcohol, and sixteen cubic centimeters of 

 strong acetic acid. Upon cooling the solution, and allowing it slowly 

 to evaporate in the air, large brilliant deep-blue crystals, which appar- 

 ently belong to the monoclinic system, slowly separated.* 



The same substance may be obtained in a similar manner from 

 cupric acetate and amnionic bromide, after treating with ammonia and 

 afterwards with acetic acid. 



The new compound is only very slightly soluble in pure alcohol, and 

 is decomposed at once by water into impure cupric hydroxide, am- 

 nionic acetate and amnionic bromide. The cupric hydroxide contains 

 large amounts of basic cupric bromide and acetate. 



The only satisfactory solvent for it seems to be a strong aqueous 

 solution of amnionic acetate and bromide, containing more or less 

 alcohol. By this singular mixture the compound is not decomposed, 

 even at 70° or 80° C. Acids of course at once decompose and dis- 

 solve cupriammonium acetobromide, and alkalies upon boiling set free 

 ammonia and precipitate cupric oxide as usual. The crystals are 

 fairly permanent in the air ; they are singularly brittle and rather 

 light, possessing a specific gravity of 2.134. 



In the analysis of the compound, copper was determined electro- 

 lytically after evaporation with sulphuric and nitric acids ; and the 

 bromine and ammonia were determined as usual. The accurate de- 

 termination of the acetic acid was a much harder task. Distillation 

 with phosphoric acid, according to the method recommended by Frese- 

 nius,f is not very satisfactory because of the great expenditure of time 

 which it requires, and the fact that traces of hydrobromic and phos- 

 phoric acids are always found in the distillate. Usually the two acids 

 were precipitated together from the neutralized distillate, and the 



* T. W. Richards, Ber. d. ch. Ges., 1890, p. 3791. 



t Zeit. fur Analytische Cliem., V. 315, and XIV. 172. 



