ENTOMOLOGY. 65 



g'ood and rather uniform results have been obtained Ijy the use of 

 Paris i>reen, while in an equally large nuniljer of cases the Paris green 

 was found to be unreliable. 



The author recognizes 3 classes of unsatisfactory Paris green — 

 l)ogus, adulterated, and low grade. In bogus Paris green, substances 

 are substituted for the copper and arsenic of the ordinary Paris green. 

 In adulterated Paris green, white powders, such as gypsuni or flour, 

 are added to increase its weight. In the low-grade Paris green there 

 is a low percentage of arsenious oxid in combination, and the requi- 

 site percentage of arsenic is secured by the addition of free or soluble 

 arsenious oxid. White arsenic has long been known to be injurious 

 to foliage. The chief feature of Paris green which has made it a 

 standard insecticide is its insolubility, and the addition of free 

 arsenious oxid renders the substance dangerous and worthless as an 

 insecticide. Two forms of poisoning from this substance may be 

 recognized — the acute and chronic. In acute poisoning the leaves 

 stow a ))lackening within 24 hours after the application of the insecti- 

 cide. In chronic poisoning the leaves become prematurely yellow and 

 drop oli' wdthin 3 or 3 weeks after the application is made. 



A sample of Paris green manufactured in New York City, upon 

 analysis, was found to contain 23.6 per cent of its weight of free 

 arsenious oxid which was soluble in water. Another sample sent to 

 the station contained 29.4 per cent of soluble arsenious oxid. Such 

 grades of Paris green must, of course, be condemned, as they would 

 cause excessive injury to the foliage of fruit trees. A sample of 

 barium arsenite which was analyzed at the station contained 27.64 per 

 cent of free arsenious oxid. One sample of "pink arsenoid," or lead 

 arsenite, contained only 3.24 per cent of free arsenious oxid, while the 

 content of combined arsenious oxid was 40.02 per cent. This sample 

 would not be dangerous to foliage and could be recommended. A 

 sample of copper arsenite contained 7.82 per cent of arsenious oxid, 

 and is, therefore, to be considered as dangerous. A sample of pro- 

 prietary arsenical spray known as Paragrene was examined under the 

 microscope. It was seen that the sample contained a considerable 

 quantity of gypsum and also crystals of white arsenic. An analysis 

 disclosed the fact that the sample contained 23.08 per cent of free 

 arsenious oxid, and was, therefore, dangerous. 



Considerable quantities of lime have been added to the water in 

 which Paris green is mixed in order to render insoluble the free 

 arsenic or other soluble arsenites which are present in Paris green. 

 This method is unsuccessful, however, in cases where the quantity of 

 free arsenic is large. 



Several tests may be applied for the purpose of determining the 

 purity of Paris green. Paris green dissolves freel}' in ammonia, 

 while the majority of substances which have been used for adulterating 



