LONDON PURPLE ITS COMPOSITION. 149 



Worm Destroyer," which is essentially the same as the Lodi prepa- 

 ration, and put up at the JSTew Jersey works for the Galveston firm. 

 Fifty grains of. arseniate of soda and 200 grains of dextrine are to be 

 dissolved in one gallon of cold water. The mixture formerly sold at the 

 exorbitant price of $1 per pound, and is now offered for 50 cents per 

 pound. It is put up in packages of GO and 100 pounds, and thus sold 

 at a discount of 10 per cent. It is to be used at the rate of 4 ounces of 

 the mixture to about 40 gallons of water, making the cost of one ap- 

 plication per acre about 12J cents. It has been extensively used. 



Another " pest poison," also essentially the same as the Lodi prepa- 

 ration, but faintly colored with rose aniline, is put up by the Kearney 

 Chemical Works of New York, in J- pound packages, sold at 50 cents, 

 and to be dissolved in GO gallons of water. 



LONDON PURPLE. 



This powder is obtained in the following manner in the manufacture 

 of aniline dyes : Crude coal-oil is distilled to produce benzole. This is 

 mixed with nitric acid, and forms uitro-benzole. Iron filings are then 

 used to produce nascent hydrogen with the excess of nitric acid in the 

 benzole. When distilled, aniline results : to this are added arsenic acid, 

 to give an atom of oxygen which jn^oduces rose aniline, and quicklime 

 to absorb the arsenic. The residuum which is obtained by filtration or 

 settling is what has been denominated " London purple," the sediment 

 being dried, powdered, and finely bolted. The powder is, therefore, 

 composed of lime and arsenious acid, with about 25 per cent, of car- 

 bonaceous matter which surrounds every atom. Experiments which 

 we made with it in 1878 impressed us favorably with this powder as an 

 insecticide, and its use on the Colorado potato-beetle by Professors 

 Budd and Bessey, of the Iowa Agricultural College, proved highly satis- 

 factory. We were, therefore, quite anxious to test its effect on the Cotton 

 Worm in the field on a large scale, and in the winter of 1878-'79 induced 

 the manufacturers to send a large quantity for this purpo>e to the De- 

 I)artment of Agriculture. The analysis made of it by Professor Collier, 

 the chemist of the Department, showed it to contain : 



Per cent. 



Rose aniline 12. 46 



Arsenic acid 43, 65 



Lime 21.82 



Insoluble residue , 14. 57 



Iron oxide 1. 16 



Water 2.27 



Loss 4.07 



100. 00 



Through the liberality of the manufacturers, Messrs. Hemingway & 

 Co., a number of barrels of this powder were placed at our disposal 



