OF ARTS AND SCIENCES. 23 



Parts. 

 Arsenic trioxide, 11 



Potassium carbouate, 32 



Dissolved the potassium carbonate in thirty-two parts of water, 

 added the arsenic trioxide boiled and filtered. 



Parts. 



Copper sulphate crystallized, 32 



Water, 192 



Dissolved and boiled while hot ; added, with constant stirring, the 

 hot solution of arsenic trioxide. 



Analysis No. XVII. 



99.62 

 Analysis No. XVIII. 



99.04 



In summing up, I will first call attention to the fact that in no one 

 of the eighteen samples does the arsenic exist in these compounds in 

 as great a ratio as required by Bloxam's formula. Further, they all 

 contain water, and this water is not driven off at a temperature of 

 150° C. In every case, arsenic was found in the filtrate, sometimes in 

 considerable amount, as is shown by comparison of the ratios of copper 

 sulphate and arsenic trioxide taken, and the ratios between the copper 

 oxide and arsenic, as found in the analysis. All the samples dissolved 

 in ammonia with a blue color. 



In Experiments Nos. 4, 9, and 10 almost identical amounts of sub* 

 stances were taken ; but the results, as will be seen, ditl'er widely. 



Scheele's green may, accoiding to my experiments, be described as a 



