Paris Green 65 



mixture to digest at about 50° for some time 

 on a piece of asbestos board over a low flame. 

 If the green copper aceto-arsenite does not 

 form at this point, not enough acetic acid 

 has been added. Consult an Instructor 

 before adding more than a few drops of acid 

 as too much may decompose the salt. Stir 

 occasionally — once in five minutes — and 

 when the reaction seems complete drain the 

 green product on a funnel and wash to 

 remove soluble arsenites and sodium sulfate. 

 Examin the size and shape of the particles 

 under a microscope. When dry put in a 

 clean, dry beaker and see if it ''flows" well. 



NOTES 



Paris green is one of the oldest arsenical 

 insecticides. For many years it was the 

 standard remedy for the potato beetle. It 

 is applied to the vines suspended in water. 



The composition of Paris green required 

 by the symbol is never exactly attaind, the 

 amount of arsenic being somewhat less than 

 the ideal quantity. The analysis of a theo- 

 retical compound of the formula given, of 

 two samples of Paris green carefully made, 

 and the average analysis of 494 samples 

 bot on the open market in Pennsylvania, are 

 given in the following table : 



