20 8 Mr. Chevenix’s Analysis of 
some essential cause of the greater solubility of the one than 
of the other, I resolved to examine them apart. 
One hundred parts of the first of those precipitates, exposed to 
a low red heat, lost 22. Boiled with potash, there remained 
undissolved, a blackish brown powder, which, well washed and 
dried, weighed 50. The supernatant liquor, saturated with 
nitric acid, and evaporated, was precipitated by nitrate of lead. 
Upon filtration, 82 were left, which indicate 27 of arsenic 
acid. Therefore, this arseniate of copper contained. 
Copper 
- - - 50 
Arsenic acid 
- - - 27 
Water 
- 22 
99 
The second artificial compound, which was mentioned above, 
was evidently more soluble than the latter ; and analogy might 
lead us to suspect, in arguing from the generality of salts the 
basis of which is supersaturated, that it contained an excess of 
acid. It was analyzed in the same manner as the last, and 
afforded, 
Oxide of copper - - - 35 
Arsenic acid - - 39,5 
Water ----- 24 
98,5 
Thus then have we two artificial arseniates of copper, one 
of which intimately corresponds with one of those which we 
have recognized among the productions of nature. The other 
possibly will be found, but we are not yet in possession of it; 
for I shall presently mention the reason why No. I. although 
containing 39 of acid, cannot fairly be esteemed as such. I 
