ON ARSENIATED COPPER. \Q^ 



atialyfis and thofe of cryftallography, very favourable to the 

 fubdivifion of the mineral in queftion, into four diftin£l 

 fpecies. 



But Cit. Vauquelin, on analyling a piece of lamelliform ar- Vauquelin's 

 fenialed copper, whofe cry ftals were quite frefh, obtained ^ f^n^nif rm ar- 

 very different relation between the quantities of the three prin- feniate ; 

 ciples*. His refult was as follows : 



Oxide of copper - - - 39 



Arfenic acid - - - - 43 



Water - - - - 17 



Lofs - - - - 1 



100 



It is remarkable In this cafe, that the quantity of acid ex- 

 ceeds that of the copper, while in the refult obtained by Mr. 

 Chenevix it forms only a little more than a third of the quantity 

 of copper. It is not therefore evident that the limits indi- 

 cated by this celebrated chemift are eflential to the fubflances 

 analyfed. 



The experiments of the fame philofophers on the capillary and of the ca- 

 cryftals, offer differences not lefs ftriking. According to Cit.P"'a''y"y'tals. 

 Vauquelin thefe cryflals contain, 



* Mr. Chenevix, in his memoir, gives a paffage from a letter 

 which Citizen Vauquelin had wiitten to him, and in which he in- 

 formed him, that having analyzed cryftals of the lamelliform va- 

 riety, he found that they were compofed of 59 of oxide of copper 

 and 41 of arfenic acid. Mr. Chenevix adds, that the great differ- 

 ence between this refult and that which he had himlelf obtained 

 from the fame fubftance, induced him to repeat his analyfis with 

 great care and attention, and that he conftantly found the lame 

 proportions of oxide of copper, arfenic, and water. It is very 

 probable that this refult announced by Cit. Vauquelin, and fo dif- 

 ferent on the other hand from that now given, was obtained in a 

 firft effay, or that this chemifl:, when he wrote to Mr. Chenevix, 

 trufted to his memory, which was not fo faithful as it generally is. 

 However that may have been, the only refult avowed by Cit. Vau- 

 <iuelin is that we now publith, and which he has inferted In the 

 'Journal des M.nesy No. 55, p. 562. 



O 2 Sllex 



