240 PROCEEDINGS OF THE AMERICAN ACADEMY. 



The weights gained were equal to 22.7 per cent and 22.2 per cent 

 of the original weight, while a gain of 3 NHg would have corresponded 

 to 21.51 per cent. The error of this result is not greater than might 

 have been expected, considering the fact that the deep blue powder was 

 extremely hygroscopic, and that it was necessary to weigh the tube while 

 this was still ice-cold, in order to avoid loss of ammonia. A single 

 analysis, although not exact, served to confirm sutRciently the formula 

 of the resultinor substance. 



(3) 1.809 grams of the substance required 29.6 cubic centimeters of 

 normal acid to neutralize the ammonia contained in it. This corresponds 

 to 28.2 of ammonia instead of the theoretical 30.3. The loss occurred 

 during the transferrence from the tube to the retort, for the substance is 

 excessively unstable. 



The new substance, empirically CuBrC2H30o5NH3, dissolved easily in 

 water with the formation of a fine deep blue solution, which lost ammonia 

 upon exposure to the air, and soon deposited a basic salt of copper. 

 Exposed in a dry state to dry air, the substance lost ammonia with great 

 rapidity, and turned distinctly green in color. The only green compound 

 which could be formed under these conditions was Cu(NH3)2Br.2, and 

 hence the color change was proof that the ammonia had decomposed the 

 original cupriammonium acetobromide according to this reaction : — 



2 Cu(NH3)2BrCoH302 + 6 NH3 = Cu(Br)26 NH3 + Cu(CoH30.).,.4NIl3. 



Upon exposure to the air the compound CuBroGNHg, which has re- 

 cently been discovered in this laboratory,* is known to lose ammonia 

 with conversion into the likewise newly discovered CuBr2 . 2 NH3. 



The other compound represented above, Cu(C2H30o)4 NH3, has not 

 heretofore been made. Foerster, who tried to prepare it, was unable to 

 make cupric acetate absorb anything like its full complement of ammonia, 

 because he did not cool the mixture. f The only step necessary for the 

 final proof of the reaction given above was then the preparation of 

 diammon cupriammonium acetate, Cu(NH3)2C2H30.2 . 2 NHg, by the action 

 of ammonia gas upon cupriammonium acetate at very low temperatures. 



Under conditions precisely like those of Experiments 1 and 2, the 

 two following syntheses were made : — 



(4) (5) 



Weight of Cu(NH3)2(C2H302)o taken = 0.4380 1.0324 



Weight of substance formed = 0.5160 1.2082 



Gain in weight 0.0780 0.1758 



* Berichte der deutsch. cli. G., XXIII. 3790. t Ibid., XXV. 3416. 



