2i 6 Mr. Ckenevix's Analysis of 
is rendered much more certain and expeditious. Some iron 
will necessarily be dissolved ; and the quantity must be noted. 
The liquor, which contained muriate of copper and of iron, now 
contains only the latter. Boiled with a little nitric acid, it 
will become red ; and then ammonia, or potash, will give a red 
precipitate, which, well washed and dried, will represent 61 per 
cent, of metallic iron. All these metals having thus been pre- 
cipitated, no constituent part of the ore, except the sulphur, 
which, in the first treatment, had been converted into sulphuric 
acid, is contained in the liquor ; and from it, when neutralized, 
this latter may be precipitated by nitrate of barytes, which will 
represent 14,6 per cent, of sulphur. The absolute necessity of 
constantly using pure alkalis, in this method of analysis, is too 
evident to be insisted upon. 
GENERAL VIEW OF THE FOREGOING ANALYSES. 
In taking a retrospective survey of the experiments above 
related, upon the various natural arseniates of copper which we 
have examined, we shall find, 
First, that natural arseniate of copper exists in three differ- 
ent states of combination ; the first containing 14 per cent, the 
second 21 per cent, and the, third about 29 per cent, of acid. 
Secondly, that each' of these may contain different propor- 
tions of water, either as constituting a hydrate, or as water of 
crystallization. 
Thirdly, that, upon losing its water, arseniate of copper will 
pass from blue to pale green, and finally to brown, as in No. I. 
Fourthly, that No. I. is the only real arseniate of copper, all 
the others being arseniates of hydrate of copper. 
