19 
Copper, 
of carbonic acid in these ores. By distilling malachite per 
se in a glass retort, and collecting the products, he ob- 
tained some pure water, and a large quantity of gas, 
which extinguished a candle, precipitated lime-water, and 
by various tests was found to be carbonic acid. 
The Siberian malachite analyzed by Klaproth will fur~ 
nish another example of analysis. A hundred grains cal- 
cined in a moderate red heat in a covered crucible lost 
29 1- 2, which therefore is the quantity of the carbonic acid 
and water. Another 100 grains were dissolved in dilute 
sulphuric acid, and lost by effervescence 18 grains, which, 
subtracted from the 29 1-2, leaves 11.5 for the water.— 
The sulphuric solution decomposed by metallic zinc gave 
58 grains of copper. Another portion of the malachite 
was dissolved in nitric acid, and the precipitate by ammo- 
nia was entirely redissolved by an excess of this alkali, 
shewing therefore the total absence of iron. Lastly, the 
quantity of oxygen united with the copper is inferred to 
be that which must be added to the 58 and 29 1-2 to 
make up the 100, namely 12.5, 
The native carbonat when pure has precisely the same 
composition as the artificial, as Proust has clearly shewn, 
and will be presently mentioned. 
Arseniat of Copper . 
The composition of the different species of this family 
of copper ores as far as it is hitherto known is extremely 
simple, the ore when separated from its matrix containing 
nothing but arsenic acid, oxyd of copper, water, and some 
times a portion of iron. The arsenic acid is best estimat- 
ed by uniting it by stronger affinity with some other metal 
where it makes an insoluble salt of a known and invariable 
composition. Lead is the best fitted for this purpose, so 
that when the nitrat or acetite of lead is added to arseniat 
of copper, a soluble nitrat or acetite of copper is formed, 
together with a white insoluble precipitate of arseniat of 
lead. By preliminary experiments Klaproth found that 
