51 



begun the new double-hose arrangement b}^ which the oil and water 

 are kept separate until the nozzle is reached was employed. Instead 

 of producing a mechanical mixture, pure oil and pure water were alter- 

 natel}^ discharged. On one morning in trying to start live pumps Avith 

 these attachments a number of trees were sprayed with pure kero- 

 sene, resulting in the death of -iO. The new style attachment was dis- 

 carded, and no more injury was done save possibly the death of about 

 50 other trees which may be attributed to the combined effect of the 

 scale and the treatment. The trees bloomed and leaved out normally, 

 and are now bearing a magnificent crop of fruit. 



The scale was as nearly eradicated as the writer believes possible 

 with any treatment. During the course of spring and summer until 

 June 17, when the last observations were made, the writer visited the 

 orchard three times and carefully examined several hundred trees both 

 in the kerosene and crude oil l^locks, and found only two trees bearing 

 live scales. These were located in one of the kerosene blocks where 

 two applications had been made. A general inspection of the orchard 

 on June 17 revealed no further infestation of living scales. It is 

 understood, of course, that should every tree in the orchard be care- 

 fully examined a large number would no doubt show some living scales, 

 l)ut the observations have been sufficiently extensive to warrant the 

 statement that better results can rarely be obtained with any practical 

 treatment. 



SOLUBLE ARSENIC IN ARSENICAL INSECTICIDES. 



By J. K. Haywood, WasJdnglon, D. C. 



Chief of insecticide and (KjricuUdnd water laboratory, Bureau of Chemistry, U. S. Depart- 

 ment of Agriculture. 



The two insecticides to which I chiefly desire to call attention are 

 Paris green and London purple. As is well known, Paris green is 

 composed of copper oxid, acetic acid, and arsenious oxid, which are all 

 combined to form copper-aceto-arsenite, in the following proportions: 



Per cent. 



Copper oxid 31 . 29 



Arsenious oxid 58. 65 



Acetic acid 10. 06 



Since this is a commercial article, small amounts of foreign matter 

 are alwa3^s present. Among these may be mentioned sodium sulphate, 

 sand, and arsenious oxid, the last of which is not combined as it should 

 be with the other two constituents, but is present in the free state. 

 It is this arsenic which is generall}^ supposed to scorch foliage when 

 applied in too large amounts. 



In California, and in the East generally, 4 per cent free arsenious 

 oxid has been adopted as being the maximum amount allowable in Paris 



