486 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 16 
Mr. A. O. Larson was elected temporary secretary and furnished the 
following reports. 
Chairman R. E. Campbell announced that there would be a dinner 
for the members and an excursion to the plants of the California Sprayer 
Co., Los Angeles, and the American Cyanamid Co. at Azusa, and also 
to the State Insectary at Whittier. 
Chairman R. E. Campbell : We will now take up the regular program 
of the day, beginning with the symposium on dusting. The first paper 
is by Mr. E. R. deOng who has returned to Berkeley. It will be read 
by Mr. J. F. Lamiman. 
THE RELATION BETWEEN THE VOLATILITY AND TOXICITY OF 
NICOTINE IN SPRAYS AND DUSTS 
By E. R. deOng, University of California 
Abstract 
Free nicotine is very volatile, while nicotine sulfate is nonvolatile. The toxicity 
of nicotine solutions varies in proportion to their conversion from the salt form to the 
free alkaloid. The volatilization curve of nicotine is almost an exact parallel of 
the curve of toxicity both of fumigation and spraying. Dust carriers follow this 
same law, i. e., an inert material does not free the nicotine as does an active carrier 
and, hence, is less efficient. 
The efficiency of nicotine sulfate sprays frequently shows marked 
variation especially when combined with different types of spreaders. 
We now know that the alkalinity of the water used as a carrier has a 
great influence on the value of the spray. Such differences must be 
even more marked when dust carriers are substituted for water, because 
of the extreme variability of the chemical nature and the physical 
action of the dusts used as carriers. 
Nicotine in the free state (levorotatory) is readily volatilized and is 
much more toxic in this stage than when combined with acids (dextro¬ 
rotatory) to form non-volatile salts. Hence, the commercial forms of 
nicotine sulfate are much less toxic than when the alkaloid is freed from 
the combining acid. Death from nicotine poisoning is the result of a 
fumigatingaction, the curve of which is very close to that from spraying 
as will be shown later. This is in harmony with the work of Mclndoo, 
Thatcher and others and goes to prove that nicotine is a tracheal or 
“respiratory” insecticide rather than a true contact spray. Exceptions 
to this are found in the treatment of caterpillars where nicotine may 
be ingested by the mouth. 
Commercial applications of the less toxic form of nicotine sulfate are 
usually made on the assumption, providing any thought is given to it 
at all, that the water used as a carrier was sufficiently alkaline to free 
