RICHARDS AND OENSLAGER. — CUPRIAMMONIUM SALTS, 79 

 (1.) Ajimon-cupriammonium Aceto-iodide, 



CU(NH3)3IC2H302. 



In preliminary experiments the following method was used for pre- 

 paring this compound. Four grams of finely powdered cupric acetate 

 were stirred with a mixture of ten cubic centimeters of water, twenty 

 of alcohol, and eight of glacial acetic acid. Ammonia gas was then 

 passed into the mixture until all the cupric acetate was dissolved and 

 the color of the solution had become deep blue. After the addition of 

 three and a half grams of ammonic iodide the solution was set aside to 

 crystallize, and in about six hours large deep blue monoclinic plates, 

 having a six-sided outline, separated out. These crystals were 

 washed with alcohol, and then dried between filter papers as quickly 

 as possible. The salt thus prepared is usually not very pure, hence 

 subsequently more alcohol was used in the preparation, with better 

 success. Even yet, however, there was much room for improvement. 

 / After many systematic experiments, which need not be detailed, the 

 following method was found to yield very excellent results. Twelve 

 grams of cupric acetate were dissolved in fifty cubic centimeters of 

 ammonia water (sp. gr. = 0.90) in a flask. After cooling, thirty cubic 

 centimeters of aqueous acetic acid (57 per cent) were added to the 

 solution, then six grams of ammonic iodide, and finally fifty cubic 

 centimeters of alcohol. Upon boiling over the water bath the mixture 

 yielded a clear deep blue solution, which deposited crystals of ammon- 

 cupriammonium aceto-iodide upon slow evaporation in the air. The 

 first very small crop of crystals deposited upon cooling was not 

 analyzed. The second served for Analysis IV. below, and the third 

 crop, which was altogether the purest and best defined in crystalline 

 form, served for Analyses V. and VIII. The substance used in 

 Analyses I., II., III., VI., and VII. was prepared by earlier less satis- 

 factory methods ; it was undoubtedly the same substance, however. 



Ammon-cupriammonium aceto-iodide consists of brilliant deep blue 

 monoclinic crystals. It is not very permanent in the air, although 

 much more so than its chlorine and bromine analogues. Upon ex- 

 posure for a long time the crystals become dull and dark in color, 

 and the substance slowly loses in weight. Water at once decom- 

 poses it, some of the copper going into solution, and the rest remaining 

 as a basic precipitate. Acids set free iodine and precipitate cuproiis 

 iodide, as might be expected. The only unexpected property of the 

 salt is the fact that it contains no crystal water, thus not maintaining a 

 strict analogy with the corresponding chlorine and bromine compounds 



