40 



INSECTICIDE STUDIES. 



From the figures given above, together with information received 

 from the various States, it appears that upon the whole the purity of 

 the Paris greens upon the American market is steadily and rapidly 

 upon the increase. 



LONDON, ENGLISH, AND PARIS PURPLES. 



The analyses of lo samples of London Purple. 1 sample of English 

 Purple, and 8 samples of Paris Purple are given in the following table 

 (III). All of these are products obtained by boiling a waste product 

 from the analine-dye industry with lime. Since it was not known at 

 the time these analyses were made that the arsenic was present, both 

 as arsenious and arsenic acids, the total arsenic was determined and 

 reported as arsenious oxid, only the soluble arsenious oxid being deter- 

 mined, instead of both soluble arsenic and arsenious oxids. 



TABLE III. Omijtoxition of L< union purples and closely allied mixtures. 



"A portion digested 40 hours with water at room temperature gave 8.11 per cent arsenious <>xid and 

 J.s:> pi-r r, Tit soluble calcium oxid. A portion digested with hot water until all the soluble arsenious 

 oxid had dissolved gave 16.45 per cent soluble arsenious oxid and :\.->i'> per cent soluble calcium oxid. 



'< A No contains \A\^ per cent nitrogen. 



This analysis was made in accordance with the Texas law regulating the sale of Paris (Ireen and 

 other Insecticide* and is good only until May 1, 1903. 



'/.Mud.- in accordance with Texas law, butgood only until May 1. I'.iu-j. 



Also contained 2.8 per cent nitrogen and <>.">7 percent potassium oxid. 



It will at once be noted that the variation in the amount of arsenic 

 in different Camples of London Purple and Paris Purple is very large. 

 In the ease of 11 samples examined more recently in thU Bureau (pub- 

 lished in Bulletin US) this variation in the arsenic content is not 

 nearly 90 great. It would, therefore, appeal 1 that the amount of this 

 constituent in Mich goods is becoming more constant in the more 

 recently manufactured Dimple-. 



The ligures for soluble arsenious oxid can not he compared with 

 those obtained more recently in this laboratory, since the soluble 

 ar-enic oxid was not determined in the earlier analyso, and it i> only 

 w'.ien both tigure> are at hand that any conclusion-; of a po>itive nature 

 can be drawn. 



