86 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 3 



ments carried out by the chemists of a cyanide manufacturing firm 

 which supplies the cyanide used in California led them to believe the 

 sodium salt was inferior to the potassium in field work. 



Under the belief that the sodium cyanide had not been given suffi- 

 ciently exhaustive tests the writer ignored all this 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 w^hich enter into hydrocyanic-acid gas genera- 

 tion. This outline of work was submitted to the Bureau of Chemistry 

 of the United States Department of Agriculture for execution. Dr. 

 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, 1909, the results of these were sub- 

 mitted to the writer in a carefully prepared manuscript and are used 

 in part in the preparation of this preliminary report. 



Results of Experiments 



Proportion of Chemicals. In using a high grade cyanide of 

 sodium it was found that a splendid generation of gas occurred when 

 the proper proportions of chemicals were taken. The results of a large 

 series of tests determined the proportion as follows : Three ounces 

 (Av.) of cj^anide, four ounces (liquid) sulphuric acid and six ounces 

 (liquid) water. Reduced to its lowest units for rapid work in the field 

 I have used 1% ounces of acid and 2 ounces of water to each ounce of 

 cyanide of sodium. This l-l%-2 formula is recommended. With a 

 pure cyanide it results in less than two per cent of gas remaining in 

 solution in the residue. The reaction, which liberates the gas from a 

 high grade sodium cyanide, produces exactly as perfect generation as 

 from a high grade potassium cyanide. One might conclude from this 

 single consideration that the sodium compound would be equally valu- 

 able in field results. It must be kept in mind, however, that these 

 experiments were carried on under the careful methods of the labora- 

 tory and not the crude ways of the field; also that past experience 

 with a 99-100 per cent article had shown it to produce results much 

 inferior to those secured from the same percentage of the potassium 

 salt. 



Field Tests. In August, 1909, one and one half acres of orange 

 trees severely infested with purple scale (Lepidosaphes heckii) were 

 fumigated with a 124^ per cent sodium cyanide, using the 1-1^/2-2 

 formula. Three strengths of gas were used, calculated from the cyano- 



^See note on p. 85. 



