New York Agricultural Experiment Station. 451 



compound as its chief constituent, with varying proportions of 

 other substitutes. The varying composition of Paris green is 

 usually due to variations in care given to the details of the pro- 

 cess of manufacture. 



Methods of chemical analysis. — ^TTie total arsenic was determined by the 

 method proposed by Thorn Smith (Jour. Am. Chem. Soc, 21 : 769) as modi- 

 fied by J. K. Haywood (same journal, 22 : 576). In determining the water- 

 soluble arsenic, J. K, Haywood's method was used (Jour. Am. Chem. Soc, 

 22 : 578), except that the Paris green was treated twenty-four hours for 

 extraotlon at the rate of one part by weight of Paris green to 1,000 parts 

 of distilled water. Ike copger was determined by electrolysis.' 



