OP ARTS AND SCIENCES. 21 



Boiled for half an hour, filtrate colorless, free from copper, but con- 

 tained arsenic ; precipitate did not blacken on boiling, was free from 

 carbonates, but contained basic sulphate. Washed until filtrate was 

 free from arsenic. 



Analysis No. XIII. 



99.30 



Experiment No. 8. 



Scheele's orijrinal receipt is very nearly one part by weight ot 

 arsenic to three each of copper sulphate and potassium carbonate, and 

 is frequently so given. The proportions as given by Scheele are, eleven 

 ounces of the first, and thirty-two of each of the otiiers. In molecules, 

 supposing the potassium carbonate to be pure and anhydrous, as he 

 directs it should be, the receipt will be as follows : — 



As A, 1- 



CuO, 2.32 



ICCOg, 4.34 



Or nearly double the amount of potassium carbonate required in the 



CuSO, + IVjCOg = CuCOg + K,SO,. 



A portion was, therefore prepared, using 



Parts. Molecules. 

 Copper sulphate 6 2.35 



Potassium carbonate, 3 2.17 



Arsenic trioxide, 2 1. 



The filtrate was slightly acid and blue, but the potassium carbonate 

 used not quite anhydrous. The color produced was fully equal to that 

 produced by the oi-diuary receipt. The filtrate contained arsenic. 



Analysis No. XIV. 



