201 
the Arseniate of Coppery and of Iron. 
No. V. Second species of the preceding Paper. This is the 
variety which, according to the description I received from 
M. Vauquelin, he had analyzed. In his letter to me, he gave 
no particulars of the method he had employed, but merely 
stated his result.* By that, it appears to contain, 
Oxide of copper - - 
1 
1 
Oa 
CO 
Arsenic acid - - - 
- " 41 
IOO 
Before the reception of his account. 
I had found, 
Oxide of copper - - 
- - 58 
Arsenic acid - - - 
Water - - - - 
100 
This induced me to repeat the analysis with the greatest 
care and attention; for I thought, that to differ from so great 
a master must be to differ from truth ; but I constantly found 
21 of water, and 21 of arsenic acid. 
This apparent difference must, therefore, depend on the 
state of dryness in which he obtained his acid ; or perhaps he 
estimated it with the water ; and, if so, I am happy to find I 
agree with him so near as one per cent. A greater preci- 
sion, as every person familiar with analysis well knows, is not 
within the power of chymical exactness. 
* J’ai analyze, ces jours derniers, une mine de caivre d’un vert clair cristallm, en 
lames hexaedres, se divisant en lames menus, et legerement flexibles, comme le mica j et 
c’est pour cela, que les naturalistes l’av.oient nomme mica vert. J’ai trouve que ce 
mineral etoit compose d’environ 59 d’oxide de cuivre, et de 41 d’acide arsenique; et’ 
c’est de veritable arseniate de cuivre. Paris, August 30, 1798. 
MDCCCI. D d 
