U. S. D. A., B. E. Bui. 90, Part III. Issued May 10, 19ii. 



HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 



CHEMISTRY OF FUMIGATION WITH HYDROCYANIC-ACID 



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 2d 

 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 cyanids 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 carried 

 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. 



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