84 HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 



tables. The quantities of acid and. water for a tree of any given size would remain 

 the same, but the weight of cyanid for use with any given measure of acid would have 

 to be reduced one-fourth. 1 



This last statement of Prof. Lounsbury assumes that the reaction 

 would require the same proportion of chemicals as with potassium 

 cyanid, an assumption which the earlier chemical work of tins inves- 

 tigation shows to be without any foundation. 



The potassium cyanid used in California for fumigation is manu- 

 factured in Germany, and is popularly styled "German" cyanid. 

 This is in distinction to a grade of cyanid made in this country, 

 termed "American" cyanid, which has had an occasional and limited 

 usage in California for a number of years. This so-called " American ' ' 

 cyanid has been popularly believed to be the very same kind as the 

 imported potassium cyanid. Such a conception has been misleading, 

 for chemical analyses have shown it to be not potassium cj^anid but a 

 cyanid of sodium equivalent to a potassium cyanid of 98 to 100 per 

 cent purity. 



This 98 to 100 per cent sodium cyanid was found by fumigators to 

 be inferior to the regular potassium salt ordinarily employed. It was 

 of very hard composition and generated so slowly that large propor- 

 tions of acid were commonly used in an attempt to hasten the reaction. 

 Some fumigators used large quantities of water, believing this was 

 necessary in order to secure the best results. Tests performed by the 

 writer showed that frequently it would require 10 to 15 minutes before 

 all the available gas was expelled from a generation of this cyanid. 

 Furthermore, the writer was informed by the president of a firm which 

 supplies most of the cyanid used in California, that extensive chemical 

 experiments carried on in its laboratory indicated that this sodium 

 cyanid produced a less satisfactory generation than did potassium 

 cyanid, and from these considerations he believed its use would never 

 be economical. The work of the firm also indicated that large pro- 

 portions of water were necessary for a satisfactory and rapid reaction. 



Under the belief that sodium cyanid had not received sufficiently 

 exhaustive tests, the writer ignored all local unfavorable evidence, 

 and, in December, 1908, outlined in detail a broad series of chemical 

 experiments to secure reliable data, with reference to this salt, on the 

 various factors winch might enter into hydrocyanic-acid generation. 

 This outline was submitted to the Bureau of Chemistry of this depart- 

 ment for execution. Mr. C. C. McDonnell, under the direction of Dr. 

 J. K. Haywood, Chief of the Miscellaneous Division, made a very 

 careful and elaborate series of determinations, and in August, 1 909, the 

 results of these tests were submitted to the writer in a carefully pre- 

 pared manuscript, which forms Part III of this bulletin. These 

 results are used in part in the preparation of the present paper. 



1 Office of Government Entomologist, Department of Agriculture, Cape ol Good Hope. "Cyanid Gas 

 Remedy for Scale Insects." July, 1905. 



