18 PROCEEDINGS OF THE AMERICAN ACADEMY 



The potash and arsenic were dissolved and allowed to cool, then 

 added to the cold solution of copper. The mixture effervesced strongly ; 

 half of it was allowed to stand until next day, then filtered ; the other 

 half was boiled, whicii operation it stood without blackening. Analysis 

 of the first half gave, — 



Analysis No. V. 



This preparation was repeated, using the same proportions ; the pre- 

 cipitate was boiled, and washed with hot water until the filtrate was 

 free from arsenic. 



Analysis No. VII. 



Copper oxide. 

 Arsenic trioxide, 

 Water, 



This seems to indicate that either the salt is decomposed by washing 

 with hot water, or that it consists of a strongly basic salt mixed with 

 free arsenious acid. The first view is most likely the correct one, if we 

 modify it so as to read : "it is decomposed by washing with either hot 

 or cold water, forming a more basic salt." 



But further experiments seem to show that this decomposition is 

 much slower with cold tlian with hot water. And I have found it 

 utterly impossible to remove the whole of the arsenic by prolonged 

 washing. 



This fact was further confirmed by an experiment of Prof. J. M. 

 Ordway, who waslied a portion of the salt with 3,000 times its weight 

 of water, without completely decomposing it. The basic salt produced 

 by washing does not blacken on boiling with water, thus showing that 

 we have a true basic salt or mixtures of several basic salts, and not a 

 mixture of Bloxam's normal arsenite, HCuAsO^, and hydrate of 

 copper. 



