﻿ARSENICALS. 53 



testinal walls into the blood and is distributed to all pails of the 

 body. A small portion of it reaches the nervous system, where il 

 apparently kills by paralysis. The way arsenic affects the various 

 tissues is not known, although Sollmann (4-9) reports that it is now 

 generally believed that the arsenicals hinder protoplasmic oxidation 

 in an unknown way. A successful insecticide must be sufficiently 

 stable to be applied to foliage without injury and sufficiently ans1 able 

 to be broken down in appreciable amounts in the bodies of the insects 

 ingesting it. 



SUMMARY. 



Arsenious oxid, commercially known as white arsenic, or simply 

 as arsenic, is the basis for the manufacture of all arsenicals. Samples 

 of commercial arsenious oxid vary in purity, fineness, apparent 

 density, and in the rate of solution m water (soluble arsenic), which 

 accounts for the diverse chemical and insecticidal results reported 

 in the literature. Arsenites are prepared by combining arsenious 

 oxid with a base. Arsenates are produced by first oxidizing ar- 

 senious oxid to arsenic oxid (arsenic acid) and then combining the 

 material with a base. Except for their water content of approxi- 

 mately 50 per cent, the paste arsenicals have the same general com- 

 position as the powdered arsenicals. 



The usual lead arsenate on the market, acid lead arsenate 

 (PbHAs0 4 ), is well standardized and stable. Basic lead arsenate 

 (Pb 4 PbOH(As0 4 ) 3 ), also well standardized and stable, is being 

 manufactured at present only to a limited extent. Chiefly because 

 of its low arsenic and high lead contents, basic lead arsenate is more 

 stable and therefore less likely to burn foliage than acid lead arsenate. 

 It possesses weaker insecticidal properties and is somewhat more 

 stable in mixtures than acid lead arsenate. 



Commercial calcium arsenate (arsenate of lime), the manufacture 

 of which is rapidly becoming standardized, contains more lime than 

 is required to produce the tnbasic form. 



Paris green, an old and well standardized arsenical, is less stable 

 and contains more " soluble arsenic" than commercial arsenates of 

 lead or lime. 



Laboratory samples of aluminum arsenate, barium arsenate, and a 

 copper barium arsenate mixture, in the powdered form, were tested. 

 The last named gave excellent insecticidal results. 



The following combinations of insecticides and fungicides were 

 found to be chemically compatible: Lime-sulphur and calcium arse- 

 nate; nicotine sulphate and lead arsenate; and Bordeaux mixture with 

 calcium arsenate, acid lead arsenate, zinc arsenite, or Paris green. 

 The following combinations were found to be chemically incompat- 

 ible : Soap solution with either calcium arsenate or acid lead arsenate ; 

 kerosene emulsion with either calcium arsenate or acid lead arsenate; 

 and lime-sulphur with acid lead arsenate. 9 Combined with nicotine 

 sulphate, calcium arsenate always produces free nicotine, and unless 

 a decided excess of free lime is present soluble arsenic is produced. 



The combination of sodium arsenate with Bordeaux mixture as 

 used in the experiments here reported gave no soluble arsenic. 



s According to the Bureau of Entomology, this combination in large amounts is used successfully in the 

 field. 



