504 
Journal of Agricultural Research 
Vol. XXIV, No. 6 
PRJSPARATION 
In France, Vermorel and Dantony {32), who experimented with iron 
arsenate for several years, recommended that it should be prepared as 
follows in order to get the maximum adhesive power: 400 grams ferrous 
sulphate in 10 liters of water is added to an equal amount of arsenate of 
soda in 10 liters and stirred constantly. This stock solution is diluted 
to 100 liters and will contain about 200 gm. ferrous arsenate per hectoliter. 
USE AS AN INSECTICIDE 
upon its use as an insecticide Smith {28) reports the use of arsenate of 
iron containing 45 per cent arsenious oxide on elm at the rate of 
pounds to 100 gallons of water without injury, and that it had good 
insecticidal qualities. Vermorel and Dantony {32) used iron arsenate 
against the codling moth in 1906, 1907, and 1908 and concluded that the 
action of iron arsenate is equal or superior to lead arsenate, with the 
advantages of color, presence of iron versus lead, and cheapness. They 
concluded that the combination of iron arsenate with copper fungicides is 
not practicable, first, because such combination is not necessary, and, 
second, because it is very destructive to foliage, and recommend that 
iron arsenate be used alone and in no case combined with copper. Taylor 
(jj, p. 13) reports the use of iron arsenate against the fall webworm in 
1909, using I to 3 pounds to 50 gallons with promising results and no 
injury to peach foliage. Melander (19) says iron arsenate is a new spray 
that has the merit of cheapness, but that it is not on the market. He 
gives brief directions for its preparation, but does not discuss results 
obtained from its use. Scott and Siegler (25) concluded that iron 
arsenate was a slow-acting poison. In field tests on apple they found 
that it was not an effective insecticide for the codling moth used at the 
rate of i pound to 100 gallons. When used at greater strengths, however, 
they thought that it should give fairly satisfactory results, but that it 
would have no advantage over arsenate of lead. 
hHAD ARSENATES 
PREPARATION 
Arsenate of lead for use as an insecticide is usually prepared by one 
of two methods, according to Haywood and McDonell (12). First, by 
using lead acetate and disodium arsenate when a precipitate of tri- 
plumbic lead arsenate, Pb3(As04)2, is formed, or, second, by using 
nitrate of lead and disodium arsenate when a precipitate of diplumbic 
lead arsenate (PbHAsOJj is formed. 
COMPOSITION 
Theoretically the tri-plumbic lead arsenate contains 74.40 per cent 
of lead oxid (PbO), 25.60 per cent of arsenic oxid (ASgOg), and 2.59 
per cent water of constitution. 
On account of various conditions, the commercial lead arsenate only 
approximates the percentages given above. This will be obvious for the 
following reasons: Chemically pinre salts are too expensive to use in its 
manufacture, while various conditions such as temperature, concentra¬ 
tion, etc., affect the reaction indicated by theory. Recent work by 
some investigators tends to show that-the lead arsenate commonly on 
