RICHARDS AND MERIGOLD. — BROMIDES AND SULPHOCYANATES. 135 



3. Tetramjion-Cuprosammonium Brojiide, CuoBr2(NH3)g(7). 



This compound is prepared by placing dry, finely powdered cuprous 

 bromide in a bulb tube which is packed in ice, and passing in dry am- 

 monia gas until the mass is saturated. The ammonia is absorbed with 

 evolution of heat, the white cuprous bromide meanwhile turning dark 

 brown and becoming hard and lumpy. In order to insure saturation, the 

 mass must be removed from the tube occasionally and powdered. The 

 saturated compound is a black powder, decomposed by water, soluble in 

 ammonic hydrate and nitric acid. It is excessively unstable, giving off 

 ammonia with the greatest ease. On this account the substance must be 

 weighed while ice-cold, and hence also its analysis is far from satisfac- 

 tory. The copper was determined in the residue from the ammonia 

 determinations, in order to be sure of the proportion of copper to am- 

 monia. The atomic proportions obtained in this way show that the 

 formula given above is probably correct, although the analyses cannot be 

 considered sufficiently definite to furnish conclusive proof. It is certain 

 that the compound contains at least six molecules of ammonia. 



Analyses of Cu2Br2(NH3)g. 

 I. 0.3276 gram of substance, distilled with caustic potash, required 

 50.30 cubic centimeters of a decinormal acid solution for neutrali- 

 zation. 

 II. 0.5746 gram of substance, distilled with caustic potash, required 

 87.03 cubic centimeters of a decinormal acid solution for neutrali- 

 zation. 

 III. 0.3276 gram of substance, — residue from I., — gave on electrolysis 

 0.1027 gram of copper. 



Calculateil for Found. 



CuoBr, . 6 NH3. I. II. 



Copper 32.66 .... .... 



Ammonia 26.29 26.20 25.84 



Atomic ratio of copper to ammonia found = 1 : 3.10. 



4. Triammon-Ccprosammonium Sdlphocyanate, Cu2(NH3)5(SCN)2. 



This substance is prepared by a method similar to that used in the 

 preparation of the saturated bromine compound described above. Dry 

 ammonia gas is passed over dry powdered cuprous sulphocyanate, until 

 the solid is saturated, the cuprous sulphocyanate being cooled by ice. 

 The substance is a black powder, and possesses no remarkable properties. 



