94 proceedings op the american academy. 



Compound No. 6, 



It is apparent that all the compounds described in this paper may 

 be arranged in a series, based upon the formulaj so multiplied as 

 to include eight molecules of the cuprianiline group Cu(Ccn7N)"-. 

 At one end of this list stands cuprianiline bromide, and at the other 

 should stand cuprianiline acetate. Only six of the seventeen com- 

 pounds necessary to fill out this scheme have been found : — 



1. Cu,(CeH,N)ieBri6. 



4. Cu«(C6H,N)i6(C2H302)3Bri3. 



2. Cu«(C6H,N)ic(C2H302),Br8. 



5. Cu8(CeH,N)i„(C2H30,)i„Br4. 



6. Cu,(C6H,N)i6(CJ430,)i5Br. 



These compounds exhibit a change in properties which corresponds 

 to the progressive change in composition. The stability of the product 

 and its difficulty of decomposition increases as the per cent of bromine 

 decreases. The violence of the reaction with a drop of strong nitric 

 acid increases in the same way. As the acetic acid increases and the 

 bromine diminishes, the crystalline form becomes less and less evident, 

 the first compound consisting of well marked crystals, and the last of 

 an impalpable powder. The average color of the substance becomes 

 blacker and bluer as one proceeds in the same direction. The prepa- 

 ration seems to depend upon two factors : in the first place, upon the 

 relative proportions of cupric acetate and bromide taken at the start, 

 and in the next place, upon the time required for the crystallization. 

 When the conditions of temperature and dilution are such that crystal- 

 lization takes place at once, a crystalline compound, rich in bromine, 

 separates. When, on the other hand, many hours elapse before the 

 substance appears, a powder very poor in bromine is formed. It is 

 possible that the inversion temperature of these double salts may vary 



