U. S. D. A., B. E. Bui. 90, Part II. Issued May 10, 1911. 



HYDROCYANIC-ACID GAS FUMIGATIOX L\ T 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 winch 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 



83 



