238 Repokt of the Chemist of the 



have been frequent complaints on the part of farmers that Paris 

 green has proved inefficient in so many instances as to lead to 

 serious suspicions in regard to its purity. As a result of such 

 complaints, the State legislature, in March, 1898, passed a law 

 intended to prevent fraud in the sale of Paris green; but no ap- 

 propriation was made for the enforcement of the provisions of 

 the law and no work was done until 1899. 



• During 1899 samples of Paris green were collected and the 

 results of analysis of these samples are presented in this bulle- 

 tin. Some materials were collected which were found in the 

 market as insecticides, but Avhich contained little or no Paris 

 green. A general statement of the composition of these will also 

 be given, as information of this kind is often desired. 



CHEMICAL COMPOSITION OP PARIS GREEIT. 



There is more or less confusion as to the exact chemical com- 

 pound that goes under the name of Paris green. Many chemical 

 writers include two different arsenic compounds under this name, 

 but the compound most frequently met in commerce contains 

 cop'per, arsenic and acetic acid, and is chemically known as copper 

 aceto-arsenite; in the trade this compound, in a form not chemi- 

 cally pure, is known as Paris green, Schweinfurt green. Imperial 

 green, Erench green. Emerald green, etc. 



Paris green,' or copper aceto-arsenite, when chemically pure, 

 contains the following amounts of the different elements indi- 

 cated : 



Arsenic 44. 44 per ct. 



Copper 24 . 99 " 



Oxygen 25 . 25 " 



Carbon 4. 73 " 



Hydrogen 0.59 " 



Paris green may be regarded as approximately consisting of — 



Copper arsenite 82 per ct. 



Copper acetate 18 " 



