!New York Agricultural Exi-erlment Station. 453 



DISCUSSION OF RESULTS OF CHEMICAL ANALYSIS. 



1. Total arscnious oxide. — In the 22 samples of materials sold 

 as Paris green, examined by us, the amount of arsenic, equiva- 

 lent to arsenious oxide, varies from 55.83 to 60.80 per ct., and 

 averages 57.05 i^er ct. This average is about one-half of one per 

 ct. higher than that found last year, and is about one and one- 

 half per ct. below the equivalent of arsenious oxide contained 

 in pure copper aceto-arsenite. So far as the total arsenic con- 

 tent is concerned, the amount found indicates a high quality 

 of Paris green. The variation is about the same as last year 

 and, excepting two samples, is within surprisingly narrow limits. . 

 The lowest amount of arsenious oxide is nearly six per ct. above 

 that required by law, viz.: 50 per ct. Were the total amount of 

 arsenic present in Paris green the only point to be considered, 

 the quality would be regarded as very satisfactory, but we must 

 consider at the same time the amount of water-soluble com- 

 pounds of arsenic present in Paris green. 



2. Water-soluhle compounds of arsenic. — The presence of water- 

 soluble arsenic in Paris green is seriously objectionable, owing 

 to the fact that soluble arsenic compounds injure foliage. Hil- 

 gard, of California, states that in the dry climate of California 

 Paris green injures foliage when it contains an equivalent of 

 more than four per ct. of arsenious oxide in the form of water- 

 soluble arsenic compounds. The water-soluble arsenic most 

 commonly occurring in Paris green is in the form of arsenious 

 oxide, commercially known as common white arsenic. 



The method of analysis used by us in determining the amount 

 of water-soluble arsenic compounds in Paris green should show 

 the full amount of such compounds that would be found in 

 actual field work where Paris green is mixed with water at the 

 rate of one part by weight of Paris green to 1,000 parts of water 

 and the mixture used soon after preparation. By longer extrac- 

 tion with water, larger quantities of soluble arsenic compounds 

 can be obtained ; but for our purpose, it is desirable to approxi- 

 mate the amount likely to be found in actual field practice in 



