the Arseniates of Copper , and of Iron. 199 
gave a proportion of 6g ; and 4 were expelled by heat 
from this salt. The composition of arseniate of lead, there- 
fore, is, 
Arsenic acid - - - - 
33 
Oxide of lead - - - - 
63 
Water - 
jL 
100 
This experiment, repeated several times, never gave 1 per 
cent, difference in the results. Another method, which may be 
deemed shorter, and perhaps even more accurate, to analyze 
arseniate of copper, is as follows. After the quantity of water 
has been estimated, the remainder may be treated by either of 
the fixed alkalis, which will combine with the acid, and leave 
the brown, the only real, oxide of copper, in the same state as 
that in which it existed in the ore ; the alkaline liquor may be 
neutralized, as above, and the proportions determined in the 
same manner. 
No. I. Third species of the preceding Paper. One hundred 
parts, exposed to a low red heat, lost nothing of their weight. 
Dissolved in dilute nitric acid, decomposed by nitrate of lead, 
and precipitated by evaporation, and then by alcohol, they left 
a white powder, which, well washed and dried, weighed 121. 
But 121 of arseniate of lead, contain 39,7 of arsenic acid. 
The nitrate of copper, boiled with potash, left a precipitate, 
which weighed 60. Therefore, there are in this variety, 
Oxide of copper - - - - 60 
Arsenic acid - - - - 39,7 
99 >7 
No. II. Fourth species of the preceding Paper. One hundred 
parts, exposed to a low red heat, lost 16. Treated as above, 
