U. S. D. A., B. E. Bui. 90, Part II. Issued May 10, 1911. 
HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 
THE VALUE OF SODIUM CYANID FOR FUMIGATION 
PURPOSES. 
By R. S. Woglum, M. S. A., 
Special Field Agent, Bureau of Entomology . 
INTRODUCTION. 
The present treatise comprises the results secured with sodium 
cyanid during the investigation of the use of hydrocyanic-acid gas 
for the fumigation of citrus trees in California and is supplementary 
to the extended report on the use of potassium cyanid. The results 
with the sodium salt are issued as a separate part of the report in 
order to avoid confusion between its use and that of the universally 
used potassium cyanid. 
Numerous cyanids which will furnish hydrocyanic-acid gas are 
known to chemists, but only two ; those of potassium and sodium, 
possess all the requirements essential for commercial work. Potas- 
sium cyanid was the chemical first used in California in the genera- 
tion of hydrocyanic-acid gas, and has continued to be employed for 
this purpose until to-day it is popularly considered, both in this 
country and abroad, as the only source from which gas can be econom- 
ically made. The grade of potassium cyanid furnished during recent 
years for citrus fumigation in southern California has generally been 
of such a high degree of purity that no special effort has ever been 
made to find a substitute. 
With the exception of fumigation, sodium cyanid is used more 
extensively for general commercial purposes than potassium cyanid. 
C. P. Lounsbury, government entomologist of Cape Colony, was the 
first to call particular attention in literature to sodium cyanid for 
fumigation when, in 1905, he wrote: 
It is possible that within a few years cyanid of soda will be used, instead of cyanid of 
potash, as the source of the gas. The soda compound gives off more gas from a given 
weight and costs no more; hence by its use some saving may be made in both original 
cost and transportation charges. But the reaction with acid appears to be more violent 
than with potash salt, which is a disadvantage owing to a greater risk of the covers 
getting burnt, and its adoption would necessitate an entire revision of our fumigation 
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