ARSKNTCALS. 53 
testinal walls into the blood and is distributed to all parts of the 
body. A small portion of it reaches the nervous system, where it 
apparently kills by paralysis. The way arsenic affects the various 
tissues is not known, although Sollmann (4#) 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 unstable 
to be broken down in appreciable amounts in the bodies of the insects 
ingesting it. 
SUMMARY. 
Arsenious oxid, co mm ercially 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 in 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 
(PbHAsOJ, 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 tribasic 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. 
