OF ARTS AND SCIENCES. 89 



Experiment No. 2. 



80 grams arsenic trioxide dissolved in water. 

 100 „ copper acetate „ „ „ 



The copper salt was added to the solution of arsenic trioxide : as in 

 the former case, a yellow-green flocculent precipitate was produced, 

 which was graduMlly converted by boiling into the brilliant aceto- 

 arsenite. The filtrate from the pigment was acid, of a deep blue color, 

 and contained arsenic trioxide, copper, and acetates. 



The precipitate wasdiied at 100° C. as before, and gave on analysis 

 these results : — 



Analysis No. IV. 



99.18 



These two salts approximate to Ehrmann's formula, although they 

 vary somewliat from it. In 1858,* " N. Reilter found in four com- 

 mercial Schweinfurt greens (No. I. was pure, II.-IV. were mixed with 

 heavy spar and gypsum, all four samples showed the presence of free 

 arsenious acid, they were washed before analysis), after deducting 

 the water and impurities : — 



100.00 101.00 100.00 100.00 



" He says it follows from these numbers that Schweinfurt green con- 

 sists of monarseiiite of copper, combined with vai-ying amounts of basic 

 (not mono) copper acetate." 



It will be seen, by comparison of these results with those obtained 

 by Ehrmann, that they with one exception contain less acetic anhydride 

 and more arsenic trioxide and copper oxide, while they do not approach 

 the composition of the commercial samples analyzed by myself. Thia 

 is, I think, partly due to an admixture of free arsenic trioxide. 



* Jahresbericht der Cliemie, 1858, Seite 651. 



