20 PROCEEDINGS OF THE AMERICAN ACADEMY 



None of the above blackened on boiling with water, and all gave a 

 blue solution with ammonia. Nos. VIII., IX. closely approximate a 

 mixture of tribasic sulphate with Bloxam's salt; while No. X. is 

 more basic than the formula for triarsenite calls for. 



Experiment No. 6. 



Molecules. 



Copper sulphate, 6 



Sodic carbonate, 3 



Arsenic trioxide, 1 



The filtrate was blue and acid ; the precipitate gave, — 



Analysis No. XL 



This corresponds with a mixture of tribasic arsenite and sulphate, 

 with a little excess of copper oxide. 



To the blue filtrate from the above, three molecules more of sodic 

 carbonate were added, the filtrate was faint yellow, and free from 

 copper, but contained arsenic; the precipitate contained a little car- 

 bonate. 



Analysis No. XII. 



99.77 



These precipitates both dissolved in ammonia with a blue color, and 

 stood boiling without change of color. 



Experiment No. 7. 



Molecules. 



Copper sulphate, 6 



Potassium carbonate, 6 



Arsenic trioxide, 1 



