ECONOMIC USE OF HYDROCYANIC ACID GAS 3 



was watched with keen interest by those whose trees 

 were fast being ruined by the scales. Many growers 

 became impatient to know the remedy so carefully 

 guarded by the experimenters. Finally, a number of 

 horticulturists about San Gabriel asked Prof. E. W. 

 Hilgard, of the University of California, for a chemist 

 to experiment in their orchards with various gases. 

 F. W. Morse was detailed for this work, and found, 

 like Mr. Coquillett, that hydrocyanic acid gas was by 

 far the most satisfactory. In the course of these ex- 

 periments certain parties who had witnessed the former 

 experiments recognized the odor of gas, and thus the 

 secret, so zealously guarded, was given to the public. 

 Although discovered and used by Mr. Coquillett and 

 his associates six months previous to the announce- 

 ment of Mr. Morse, the first general information about 

 the gas as an insecticide was given to the public by 

 the latter gentleman in a Bulletin (No. 71) from the 

 University of California Experiment Station. 



Extensive experiments were continued by Mr. 

 Coquillett. In July, 1887, he was again made an 

 assistant of the Department of Agriculture, and did 

 more than any other person to develop and perfect the 

 present methods of fumigation. The main difficulty 

 encountered in these early experiments was the inju- 

 rious effect the gas had upon the foliage. The injury 

 was lessened greatly by the ' ' soda process ' ' of Morse, 

 which consisted in adding ordinary baking soda to the 

 cyanide solution, using something like two and a half 

 times as much soda as there was cyanide in the solu- 

 tion, the result being the production of carbonic acid 

 gas, thus diluting the hydrocyanic acid gas. 



