14 PROCEEDINGS OF THE AMERICAN ACADEMY 



dently a translation, either directly or indirectly, from the same 

 author. 



The description of copper arsenite in the French edition of Ber- 

 zelius, Paris, 1847, is as follows: "The neutral salt is obtained by 

 precijiitatinLT sulphate of copper by arsenite of potassa. The precipi- 

 tate is green. When it contains an excess of base, its color is more in- 

 tense ; but it decomposes spontaneously, in a little time becoming a dark 

 brown, and then contains cupric arsenate and cuprous arsenite. Caustic 

 ammonia dissolves this salt into a colorless liquid containing, probably, 

 cuprous arsenate." The German of 1838 is the same as the above, 

 with the exception that it reads : " When the alkali is in excess, the 

 color is more intense, but it decomposes in a little time," &c. " This 

 salt " referred to in the above paragraph, is evidently the brown salt, 

 and not the green. Moreover, the German text, and not the French, 

 is the coi'rect one, as is shown by my own experiments. 



In this connection, the following extract is of interest. Rose says 

 of Scheele's green : " This precipitate is soluble in an excess of ammonia, 

 also in an excess of hydrate of potassa. The solution has in both cases 

 a similar blue color. The blue solution formed by hydrate of potassa 

 deposits in time reddish-brown suboxide of copper ; the liquid becomes 

 colorless, and contains arsenate of potMssium. The blue solution formed 

 by ammonia is not modified by time." 



The reference from Berzelius seems to have been misunderstood by 

 German as well as English writers, as the same statement occurs in 

 the Handworterbuch der Chemie, B. 2, 1858, p. 300, which says 

 Scheele's green dissolves colorless in ammonia as arsenic acid and 

 cuprous oxide. Graham-Otto * also repeats the same. 



In the New Chemistry,! the above blunder is repeated, and two 

 formulas are given, as follows : " Arsenite of copper, (Cu.,0)2As.,03 or, 

 Cu./AsO,)^." And the article finishes by saying there are also two 

 hydrated salts, CuH_,(As0.5)2, and CuHAsOn. The percentage com- 

 position of these salts would be as follows, supposing the above formulas 

 are correctly given : — 



* Vol. III., 557, 4th ed. 



t Chemistry, Theoretical and Practical. Lippincott & Co. ; Phila., 1876, 

 p. 260. 



