of Copper and of Iron. 147 



No. V. Second fpecies of the preceding paper. This is the 

 variety which, according to the defciiption I received from 

 M, Vauquelin, he had analyfed. In his letter to me, he gave 

 no particulars of the method he had employed, but merely 

 ftated his refult*. By that, it appears to contain. 

 Oxide of copper ~ ~ 59 



Arfenic acid - - - 41 



100 



Eefore the reception of his account, I had found. 



Oxide of copper - - 58 



Arfenic acid - - - 2 1 



Water - - - - 21 



100 

 This induced me to repeat the analyfis with the greateft 

 care and attention ; for I thought, that to differ from fo great 

 a maftcr muft be to differ from truth ; but I conftantly found 

 21 of water, and 31 of arfenic acid. 



This apparent difference muft, therefore, depend on the 

 liate of drynefs in which he obtained his acid ; or perhaps 

 he eftimated it with the water; and, iffo, I am happy to 

 find I agree with him fo near as one per cent. A greater 

 precifion, as every pcrfon familiar with analyfis well knows,- 

 is not within the power of chemical exaclnefs. 



No. VI. Flrjl fp:cies of the preceding paper. One hun- 

 dred parts, expofed to a low red heat, loft miich more than 

 any of the other kinds; the deficit amounted to 35. The 

 ufual treatment gave 49 of oxide of copper, and only 14 of 

 arfenic acid. I repeated this analyfis with fome portions 

 which had not been expofed to heat, and never found more 

 than 14 of arfenic acid. This arfeniale contains, 

 Oxide of copper - - 4^ 



Arfenic acid - - - 14 



Water - - - - 



[To be contiiiutJ.] 



.i:) 



98 



• J'ai analyif-t ccs jours dcrniers, une mine de ruivre d'lin vert d.iir 

 ciitlallin, en latnes litxacdrts, i"c divilniit en lim<s menus, ei Itgtrtmyut 

 Hcxi!)ic«, comuic If mica J ct cVft pour ctla, que Ics naturalises I'avoinnt 

 noiTiniw mira -jcn. J'ai trfiuvc <|uc cc mini'ral i-'uit coiTipt/ci d'cnviroti 

 59 d'oxide de cuivrc, tt de 41 d^icid.: arrcniijyc; ct c'cft dc veri'ablc 

 arfcniate de cuivre. Pari^j -Auguft jo, i7<)S. • 



K a XXVri. On 



