New York AcricutruraL 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 analysts.—The 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 
extraction at the rate of one part by weight of Paris green to 1,000 parts 
of distilled water. The copper was determined by electrolysis. 
