U. S. D. A., B. E. Bui. 90, Part III. Issued May 10, 19lt 
HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 
CHEMISTRY OF FUMIGATION WITH HYDROCYANIC-ACIB 
GAS. 1 
By C. C. McDonnell, 
Chief , Insecticide and Fungicide Laboratory, Miscellaneous Division, Bureau of Chemistry, 
INTRODUCTION. 
The Miscellaneous Division of the Bureau of Chemistry was 
requested by Mr. C. L. Marlatt, Assistant Chief of the Bureau of 
Entomology, to analyze certain chemicals which were being us:d 
by Mr. R. S. Woglum, in charge of the field work with hydrocyanic- 
acid gas in southern California, and at the same time to investigate 
certain chemical problems in connection with this work which Mr. 
Woglum had outlined. 
In view of the great importance of the subject from an economic 
standpoint and the small amount of work that has been done in the 
study of the chemical problems involved, the question has been thor- 
oughly investigated. The action of mineral acids on cyanicls and 
hydrocyanic acid has been quite thoroughly studied by a number of 
chemists, but the important bearing of this point on the question of 
fumigation has not been brought to the attention of those engaged 
in this work with the force which it demands. 
I. ANALYSES OF CHEMICALS USED FOR THE PRODUCTION OF 
HYDROCYANIC-ACID GAS. 
SULPHURIC ACID. 
Ordinary commercial sulphuric acid is usually sold of the strength 
known as 66° Baume, which corresponds to a pure product containing 
96 per cent of sulphuric acid (H 2 S0 4 ). The specific gravity of 
commercial acid, owing to the presence of impurities, is always 
higher than that of the pure acid, and commercial acid of this grade 
will not average over 93 or 94 per cent of sulphuric acid. A sample 
1 A detailed outline of experiments covering certain problems in the chemistry of hydrocyanic-acid gas 
fumigation was submitted by the writer to the Bureau of Chemistry for execution. This work was camedl 
out under the direction of Dr. J. K. Haywood, Chief of the Miscellaneous Division, by Mr. C C McDonnell,, 
Chief of the Insecticide and Fungicide Laboratory. A report by Mr. McDonnell covering the results of this 
chemical investigation was sent to the Bureau of Entomology, August, 1909, and is here given. Certain 
important considerations included in this report have already been made public— R. S. Woglum. 
91 
