14(5 AnaJyfis of the Arfeniates 



No. T. Third [pedes of the preceding paper. One hnri- 

 dred part?, expofed to a low red heat, loll nothing of their 

 weight. Diliolved in dikite nitric acid, decompofcd by ni- 

 trate of lead, and precipitated by evaporation, and then by 

 alcohol, they left a white powder, which, well wafhed and 

 dried, weio;hed lai. But 121 of arfeniate of lead contain 

 39,7 of arfcnic acid. The nitrate of copper, boiled with pot- 

 a(h, left a precipitate, which weighed 60. Therefore, there 

 are in this variety. 



Oxide of copper - - 60 



Arfehic acid - _ _ 39)7 



99>7 

 No. II. Fourth fpecies of the preceding paper. One hun- 

 dred parts, expol'ed to a low red heat, lofl j5. Treated as 

 above, they yielded a quantity of arfeniate of lead, corre- 

 fponding to 30 of arfenic acid; and I obtained 54 of oxide 

 of copper. Therefore this variety contains,, 



Oxide of copper - - 54 



Arl'enic acid - - - 30 

 Water - - - - 16 



100 

 No. TIT. Var. 3 of the third fpecies. One hundred parts, 

 expofed to a low red heat, loll 18 of water. The 82 re- 

 maining, boiled with potafli, left a refiduum of a blackifli 

 brown colour, which weighed 51, and which, examined 

 by the different reagents, was found to be oxide of copper, 

 without mixture. The fupernatant liquor, and the liquor 

 which wa(hcd the 51 precipitated, being neutralized and 

 evaporated together, left a precipitate, by nitrate of lead, 

 which weighed 88, and, by the proportions of arfeniate of 

 kad, ell:abTi(hed above, indicated 29 of arfenic acid. The 

 proportions in this variety are therefore as follows : 

 Oxide of copper - - 51 



Arfenic acid - - - 29 

 Water - - - - 18 



98 

 No. IV. Far. 5. of the third fpecies. This gave, by one or 

 other of the two methods, already defcribed and applied, as. 

 follows : 



Oxide of copper - - 5° 



Arfenic acid - - - 29 

 Water - - - - 3i 



100 



