ON ARSENIATED COPPER. 1_9J 



Towards the concliifion of his memoir, Mr. Chenevix re- Only one true 



marks that the natural arfeniate of copper exifls in three differ- ^'^^""'T "'"u"?* 



.... 1 ,. /, o P^r: the others 



ent combinations, the fir ft of which contains 14. percent, of are arfeniates of 

 arfenicacid, (firft refult al>ive) ; the fecond contains 21, (fe- ^'^''^ateof cop- 

 cond refuh); and the third 29, (third, fourth, fifth, and fixth ^^'^' 

 refults). It is true, the third refult gave 39.7 of acid in the 

 100 parts, but as the remainder of the mafs was compofed of 

 60 parts of copper without water, he found that the propor- 

 tion of the acid with the copper did not differ much from that 

 which takes place in the varieties in which water forms a part: 

 this induced Mr. Chenevix to comprehend this refult in the 

 fame divifion. Yet he confiders this combination as the only 

 true arfeniate of copper, while the other three are arfeniates of 

 hidrate of copper. 



I feel the value of the double work from which I have given 

 this extract fo much the more, becaufe, having read the me- 

 moirs which contain the developement, I am enabled to judge 

 of the advancement which it has produced in our knowledo-e 

 on a fubjedt which was in a great meafure new when MM. de 

 Bournon and Chenevix began to be employed with it. The 

 expofiiion whicbl fl)all add of fome enquiries I have made on 

 the ciyflallization of arfeniated copper, and of the refleflions 

 which they have given rife to, have no other objed but that 

 nothing may be negle<5ted which tends to elucidate in a greater 

 degree, every thing conneded with an objedl of fuch import- 

 ance as tiie diftinftion of mineralcgical fpecies. 



After having read the cryflallographic part of the work in Can the varie. 

 queftion, I was defirous to know if it was not poffible to bring '•'^^ ^^ reduced 

 fome of the cryftais, defcribed by M. de Bournon as belonging form .' ^""''"''' 

 to different fpecies, to the fame form of the integrant molecule; 

 but not being able to make all the direft obfervations which 

 would have guided me in this enquiry, I was obliged to con- 

 fine myielf to fimple hypothefes. 



I therefore confidered the obtufe oftahedron as performing 

 the fundions of the primitive form ; and I was the more war- 

 ranted in conceiving this opinion, becaufe the celebrated Kar- 

 ilen, in a fupplement to the excellent memoir which he had 

 pubhflied be ore*, on the combinations of copper with differ- 

 ent principles, fays that the odahedron in queftion is lamellated, 



* Jourfi. de Phjfique, Brumaire, An, X. p. 342, et fuiv. 



