249 Report oF THE CHEMIST OF THE 
DISCUSSION OF RESULTS OF ANALYSIS. 
1. In the 24 samples of Paris green examined, the amount of 
arsenious oxide varied from 55.34 to 60.16 per ct. and averaged 
56.48 per ct. This average is only about 2 per ct. below the 
arsenious oxide contained in pure copper aceto-arsenite and indi- 
cates a good quality of Paris green, so far as the arsenic content 
. 1s concerned. Excepting one or two samples that run high in 
arsenic, the variation is surprisingly small. The legal require- 
ment is 50 per ct. arsenious oxide. 
2. The amount of copper oxide varies from 27.70 to 30.90 per 
ct. and averages 29.97 per ct., which is one and one-third per ct. 
below that in pure copper aceto-arsenite. The copper content 
therefore indicates a good quality of Paris green. 
3. In pure copper aceto-arsenite there are 1.87 pounds of ar- 
senious oxide for one pound of copper oxide. Now, this relation 
is of value in showing whether Paris green contains more arseni- 
ous oxide than it ought. The chief adulterant used in Paris 
green is arsenious oxide, commercially known as white arsenic. 
This is used because it is cheaper than Paris green and also be- 
cause it can be safely added without any danger of reducing the 
amount of arsenious oxide. In fact, a very poor quality of Paris 
green can be brought up to the legal requirements by addition of 
arsenious oxide. However, arsenious oxide cannot be added to 
Paris green without increasing the ratio of arsenious oxide to 
copper oxide above 1.87. In the samples examined, the ratio of 
arsenious oxide to copper oxide varies from 1.82 to 2.17 and aver- 
ages 1.88. In sample No. 14, the arsenious oxide exceeds 60 
per ct. and the copper is less than 28 per ct.; hence, the arsenious 
oxide is present in amounts more than twice exceeding the cop- 
per oxide. In other words, there is too much arsenious oxide for 
the copper oxide present and the only possible inference is that 
white arsenic has either been added purposely or is present as the 
result of carelessness in manufacture. 
