iil^ ON ARSEKIATED COPPER. 



Silex - . - - 2 



Water - ... 5 



Arfeniate of iron - - . 7 to 8 



Arfeniate of copper - - - 86 



100 

 This chemifl adds, that if the arfeniate of copper did not 

 contain any foreign matter, it would be formed of about 69 

 parts of oxide of copper and 31 of arfenic acid. 

 Klaproth's ana- We have another refult on the fame fubje6l, obtained by 



lyfis 



M. Klaproth, whofe labours have concurred fo advantageoufly 

 with thofe of Vauqiielin, to procure an exa6l knowledge of 

 the compofition of minerals. His refult gave. 



Oxide of copper - - 50.62 



Arfenic acid - - - 45.00 



Water - - - - 3.50 



Lofs - - . _ 88 



100.00* 



The quantity of copper is nearly the fame as in Mr, Chene- 

 vix's refult ; but on one fide we find 45 of acid with .3.5 of 

 water, and on the other only 29 of acid and 18 of water; 

 which is very different. 



Befides, we need only keep to Mr. Chenevix's own refults 

 to find difficulties and caufes of uncertainty ; for while this 

 Mr. Chenevi)!»s celebrated chemift obtained a very fenfible quantity of water 

 TgleelitW ^^^"^ '^^ capillary crytlals and the mammellated mafTes, thefe 

 thofe of M. de two moditications were conlidered by M. de Bournon as fimple 

 Baarnon. varieties of the third fpecies, which is the acute odahedron, 



and which gave only copper and arfenic acid without water. 

 Further, if the analyfes of the capillary cryflals and of the 

 mammellated matfes, are compared with that of the cryflah 

 in trihedral prifms, it will be feen that the differences do not 

 exceed thofe which are frequently met with between the ana- 

 lyfes of feveral pieces which evidently belong to the fame 

 fpecies of mineral. 



I add, that M. de Bournon feems to have had more au- 

 thority for confidering the capillary cryftals and the mammel- 



* Additions a la Connoijfance chimiqucs des Mintraux, p. 192. 



la ted 



