the Arseniates of Copper , and of Iron. 2.-2 r 
Some subsequent experiments, however, have induced me to 
fix the quantity of water at about 10,5. 
One hundred parts, boiled with potash, left 58,5. The liquor r 
treated as usual, by nitrate of lead, gave 31 of arsenic acid. The 
58,5 left four, which muriatic acid could not dissolve, and 
which were silica. Ammonia dissolved 9 ; and there remained 
4,5,5 of iron. This analysis presents the following result 
Silica - - ■ - 4 
Arsenic acid - - 31 
Oxide of iron - 45,5. 
Oxide of copper 9 
Which will leave for Water 10,5 
100,0 
This ore appears to be a pure arseniate, mixed accidentally" 
with a little copper ; as some of the copper arseniates casually 
give traces of iron. This is the kind mentioned by Mr. 
Klaproth, as an arseniate of copper, and the first known under 
that denomination. Heating it on charcoal, before the blow- 
pipe, he perceived a smell of arsenic, and, at length, obtained 
a metallic button, which was found to be copper. That there 
is copper in this ore, is evident from analysis. But the mere 
arsenical smell, was not a sufficient ground to- assert that it con- 
tained arsenic acid ; for this metal might, with as much proba- 
bility, have been in any other state. If indeed, that very accu- 
rate and able analyst had, upon trying the ore with the blow-pipe 
in a platina spoon, perceived no fumes, he might then have 
concluded, that the arsenic must be in the state of acid, and that 
charcoal was necessary to operate a partial reduction, to which 
the arsenic owed its volatility and its smell. But no such expe^ 
riment is reported. 
