242 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 

 is 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 gTcen 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. 



