KICHARDS AND OENSLAGER. — CUPRIAMMONIUM SALTS. 83 



Every effort to make the normal cupriammoniura aceto-iodide free 

 from the acetate was unsuccessful ; when so much of the ammonia 

 has evaporated that Cu(NIIg)3lC2Ho02 ceases to form, the singular 

 double salt which has just been described always makes its appear- 

 ance. 



(3.) Tetrammon-tricupriammonium Iodide, 

 3 Cu(NI-l3) X + 4 NH3= Cu8T6(NH3)i,. 



This interesting substance may be prepared by a method very 

 closely resembling that used for preparing ammon-cupriammonium 

 aceto-iodide. If eight grams instead of twelve of cupric acetate are 

 used with fifty cubic centimeters each of ammonia and alcohol, thirty of 

 acetic acid, and six grams of ammonic iodide, curious black cr^'stals re- 

 sembling irregular triangular pyramids make their appearance in the 

 first place. 



The new substance is similar in outward aspect to the corresponding 

 bromine compound,* although less brilliant. The crystalline faces are 

 so singularly marked and striated that an accurate crystallographic 

 study would not be feasible. They possess a distinct bronze lustre 

 which soon disappears owing to superficial decomposition. Upon ex- 

 posure to the air the substance loses ammonia and iodine, finally leav- 

 ing cuprous iodide. It is decomposed by water. Heated in aqueous 

 or alcoholic ammonia it dissolves, forming a deep blue solution which 

 upon cooling deposits bright blue needles remaining to be investigated. 



From the mother liquors decanted from the black crystals may be 

 obtained by further evaporation at first, Cu(NH3)3lCoH302, and finally 

 the mixture of Cu8(NHo)i6l(C2H..02)i5, with the coal-black hexagonal 

 crystals already mentioned. f These latter crystals are very different 

 in appearance from Cu;;(NH3)ioT6; they will be investigated in the 

 future. 



Analysis of Cu3(NHo)ioT6> 



I. 0.2049 gram of the substance yielded an amount of ammonia re- 

 quiring 18.22 cubic centimeters of decinormal acid for neutrali- 

 zation, and 0.0352 gram of copper on electrolysis. 

 II. 0.2315 gram of the substance required 20.24 cubic centimeters 

 of acid, and gave 0.0385 gram of copper and 0.2901 gram of 

 argentic iodide. 



* Richards and Shaw, These Proceedings, XXVIII. 257. 

 t See page 81. 



