22 PROCEEDINGS OF THE AMERICAN ACADEMY 



This is an almost exact mixture of tribasic sulphate and arsenite. 

 It dissolved in ammonia with a blue color, and did not blacken on boil- 

 ing. Tlie potassium carbonate may, therefore, be considerably dimin- 

 ished from that called lor in Scheele's receipt. 



Experiment No. 9. 



This was nearly a repetition of Experiment No. 4 as to quantities 

 used. The object being in this case to study more iully tlie effects 

 of washing, the proportions taken approximate closely to Scheele's 

 receipt : — 



Copper sulpliate, 

 Arseuic trioxide, 

 Potassic carbonate, 



The solutions were mixed and boiled for half an hour; the first 

 (No. XV.) was washed until the wash-water was free from sulphates; 

 the other (No. XVI.) until the wash- water was free from arsenic. 



Analysis No. XV. 



99.54 

 Analysis No. XVI. 



'Experiment No. 10. 



This preparation was made exactly according to Scheele's own direc- 

 tions, as given by himself in the Proceedings of the Stockholm 

 Academy, using the English translation for the weights and measures. 

 The sample was divided after precipitation. No. XVII. was washed 

 by decantation with the amount of water he specifies. 



No. XVIII. was first boiled with water, and then washed with hot 

 water so long as arsenic was found in the filtrate. The proportions 

 used were, — 



