258 PROCEEDINGS OF THE AMERICAN ACADEMY 



uble compound containing proportionally more ammonia than the 

 original substance. The reaction which takes place may possibly be 

 represented somewhat as follows : — 



Cu3(NH3)ioBr6 -f- 4 H^O 



= [Cu(NH3)6Br2 + 4 NH4Br + -4?] + 2 Cu(OH)o. 



The amount of water present undoubtedly determines to a large 

 extent the exact nature of the cupriammonium compound which re- 

 mains undecomposed. 



A great number of analyses of the indigo salt were made ; partly 

 because of the unusual nature of the formula which they indicated ; 

 and partly because the crystals, constantly appearing under many 

 varying conditions in the work which has just been described, needed 

 identification. 



Analyses of Cu3(NH3)ioBre. 



I. 0.4730 gr. of the substance yielded 0.1075 gr. of copper. 



II. 0.4540 gr. of the substance yielded 0.1033 gr. of copper. 



III. 0.2614 gr. of the substance yielded 0.0594 gr. of copper. 



IV. 0.4269 gr. of the substance yielded 0.5721 gr. of argentic 



bromide. 

 V. 0.4084 gr. of the substance yielded 0.5476 gr. of argentic 



bromide. 

 VI. 0.2884 gr. of the substance yielded 0.3861 gr. of argentic 



bromide. 

 VII. 0.1776 gr. of the substance yielded an amount of ammonia 

 requiring 20.67 c.c. of decinormal acid for neutralization. 

 VIII. 0.1245 gr. of the substance required 14.77 c.c. of the same 

 acid. 

 IX. 0.1099 gr. of the substance required 12.71 c.c. of the same 



acid. 

 X. 0.1288 gr. of the substance required 15.20 c.c. of the same 



acid. 

 XI. 0.1175 gr. of the substance required 13.85 c.c. of the same 

 acid. 



