204, Mr. Chenevix's Analysis of 
Sulphur - - 
Copper - - 
84 
Iron 
- - - 4 
100 
Although I have mentioned, in the preceding statements, 
only a single analysis of each specimen, it is by no means to 
be imagined, that so small a number would be sufficient to 
satisfy enquiry. None of the above results have been taken 
into account, unless confirmed by frequent repetition ; and the 
probationary experiments have been diversified, as much as lay 
in my power, by many different tests, and various chymical 
reagents. 
With regard to the colour of some specimens of arseniate of 
copper, it is easily to be accounted for upon chymical principles. 
The mistake under which we have long laboured, that the 
green is the real oxide of copper, has happily been rectified by 
M. Proust.* He has proved it to be a particular substance, 
(to which he has given the very improper name of hydrate of 
copper j'f) endowed with peculiar properties, and composed of the 
brown oxide, and of water, in a state of combination. From his 
experiments, and from what I myself have seen, I am inclined 
to draw the conclusion, that we have never yet obtained by art 
any real salt of oxide of copper. In examining, for instance, 
sulphate of copper, we find it to afford blue crystals; and to 
* Annales de Chimie, Vol. XXXII. p. 26. 
f Copper is not the only metal capable of a similar combination. Cobalt, nickel, 
and uranium, enjoy the same property. This may, in some measure, explain the change 
of colour, which the liquid muriates of some of these metals undergo by gentle heat : 
it may likewise throw some light upon the sympathetic ink of Cobalt. 
