2 BULLETIN 1312, U. S. DEPARTMENT OF AGRICULTURE 
points and to devise methods of preparation and packing which 
would make possible a more ee product. The relation of 
killing soles to the rate and extent of the liberation of nicotine when 
applied to the plants, a very important point, is not considered here, 
REVIEW OF LITERATURE 
Smith (6) describes the introduction of nicotine dusts and gives 
the history of their early manufacture. He mentions the reaction 
of lime with nicotine sulphate to form free nicotine. In his dis- 
cussion of fillers and carriers, he comments on kaolin (which he ranks 
very high), hydrated lime, quicklime, talc, sulphur, tobacco dust, 
gypsum, kieselguhr, and lime carbonate. His statement that “‘lime 
carbonate” has no effect on nicotine sulphate does not agree with 
the findings of others. De Ong (2) suggests that the results obtained 
by Smith may have been due to the kind of carbonate of lime he used. 
Headlee and Rudolfs (3) and Rudolfs (6) published data on the 
liberation of nicotine from various types of dusts. Most of these 
results are included in their later publication (4), which gives also a 
report of their thorough studies on the volatilization of nicotine, both 
under field conditions and in the laboratory, by passing air under 
definitely controlled conditions through the nicotine dusts, and on the 
relation of the rate of volatilization to insect toxicity. 
De Ong (2) presents data showing the difference in toxicity of non- 
volatile nicotine sulphate and volatile nicotine. He states that the 
toxicity of a dust varies in proportion to the change from the salt to 
the free alkaloid. 
Thatcher and Streeter (7) conducted a thorough study on the loss 
of nicotine from nicotine dusts. Their investigation included work 
on the loss of nicotine from nicotine sulphate dusts during storage 
very similar to that done in the Bureau of Chemistry. Although the 
two studies were carried on at the same time, each was conducted 
entirely independently of the other. Thatcher and Streeter divide 
fillers or carriers for nicotine sulphate into three groups: (a) Colloidal 
substances, like kieselguhr and kaolin, that tend to prevent volatili- 
zation; (6) crystalline substances, such‘as sulphate and gypsum, that 
are inert; and (c) all the common hydroxides and carbonates which 
are ‘‘active;” that is, change the nicotine sulphate into the more 
volatile free nicotine. In studying the effect of storage on nico- 
tine dusts, they found significant losses from the calcium carbonate 
and calcium hydroxide dusts, especially the carbonate dust, even in 
sealed containers. They suggested that this might be due to some 
chemical change in the nicotine. 
Campbell (1)presents a historical review of nicotine dusting, which 
ncludes a complete bibliography. 
OUTLINE OF EXPERIMENTS 
In preparing the mixtures used in the investigation here reported, 
two commercial nicotine solutions, a 40 per cent solution of nicotine 
sulphate and a 40 per cent solution of free nicotine, were used. Kiesel- 
guhr, kaolin, talcum, calcium hydroxide, calcium carbonate, and plas- 
ter of Paris were the carriers or absorbents. Grades of the usual com- 
mercial purity and degree of fineness were used, so that the results 
might be comparable with those obtained in commercial practice. 
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