1912.] PUBLIC DOCUMENT — No. 31. 183 



A. Paris Green. 

 Historical. 



Paris green was produced by Russ and Sattler ^ in 1814. 

 The process was kept a factory secret until revealed by the inde- 

 pendent investigations " of J. Liebig and Henri Braconnot in 

 1822. Liebig ^ treated 4 parts of verdigris in acetic acid with 3 

 parts of arsenous oxide in boiling acetic acid. The acid re- 

 tained the material in solution until the excess was expelled. 

 Braconnot * prepared a solution of potassium arsenite by boiling 

 6 parts of arsenous oxide with 8 of potassium carbonate, poured 

 it while warm into G parts of copj)er sulfate, dissolved in a 

 small quantity of warm water, and added acetic acid until the 

 odor was perceptible. The methods of Liebig and Braconnot 

 have since been modified by many chemists, but substantially 

 they typify the two distinct manufacturing processes employed 

 to-day, i.e., the instantaneous and the slow. 



The instantaneous method is thus described in Watts' " Dic- 

 tionary of Chemistry: " ^ " Five parts of verdigris are made up 

 to a thin paste, and added to a boiling solution of 4 parts or 

 rather more of arsenous acid ^ in 50 parts of water. The boil- 

 ing must be well kept up, otherwise . . . acetic acid must be 

 added." 



The slow process, as given by a manufacturing company,'^ is 

 as follows: 1,000 pounds of blue vitriol are dissolved in 480 

 gallons of hot water and run into a 1,200-gallon '' striking vat." 

 Four hundred and fifty pounds of sodium carbonate (Solvay) 

 are dissolved in 480 gallons of hot water, and 795 pounds of 

 arsenic " sprinkled " on and boiled to remove carbonic acid. 



The boiling arsenic solution is " let down " into the blue 

 vitriol solution, the temperature of which is about 140° F., well 

 stirred, and 210 pounds of acetic acid (100 per cent.) mixed 

 with an equal weight of cold water added. The mixture is 



> B. B. Ross, Ala. Exp. Sta., Bui. No. 58, p. 4 (1894). 



2 H. Sattler, Ztschr. Angew. Chem., 1888, p. 35. 



3 Repert. far die Pharm. 13, pp. 446-457 (1822). 



4 Ann. Chim. et Phys. Ser. 2, 21, pp. 53-56 (1822). 

 '3d edition, 1, p. 10 (1893). 



' C. L. Bloxam states equal parts by weight of arsenic and copper acetate. (See Chemistry, 

 9th edition, p. 271 (1907).) 



' From correspondence on file. 



