22 



CIRCULAR 3 7 3, U. S. DEPARTMENT OF AGRICULTURE 



the same in both cases, the higher kill with the larger quantity must 

 have been due to the larger quantity of hydrocyanic acid gas in the 

 air. 



TESTS WITH LIQUID HYDROCYANIC ACID 



As previously indicated, compounds nos. 3 and 4 are sold on a 

 basis of the net weight of hydrocyanic acid per can, and the contents 

 cannot be divided accurately into smaller quantities. In view of 

 this condition it was not possible to determine the value of smaller 

 quantities of either of these materials. However, since the active 

 killing agent in all the compounds tested is hydrocyanic acid gas, 

 tests were begun with liquid hydrocyanic acid. 



For experimental work a storage cylinder containing the liquid 

 was brought into the fumigating house. By the proper manipula- 

 tion of valves the liquid was permitted to flow into a measuring 

 glass. The valves in the cylinder were then closed, and the measured 

 quantity of liquid hydrocyanic acid was released into a flat metal 

 pan, from which it volatilized quickly. 



Tests were run with different amounts of chemical and for dif- 

 ferent periods of time, using Japanese beetle grubs as indicators 

 of toxicity. The results are given in table 4. 



Table 4. — Mortality of Japanese beetle larvae from different periods of exposure 

 to varying quantities of liquid hydrocyanic acid per 1,000 cubic feet 



Quantity of hydrocyanic acid (ounces) 



Time of 

 fumigation 



Tempera- 

 ture 



Larvae found 



Normal 



Sick 



Dead 



4 



Minutes 

 120 



90 

 60 

 30 



120 

 90 



120 

 90 



° F. 

 75-77 

 75-77 

 75-77 

 75-77 

 75-78 

 75-78 

 76-78 

 76-78 



Percent 

 

 

 

 

 

 

 

 4.6 



Percent 

 

 

 

 

 

 



33.8 

 60.7 



Percent 

 100 



4 . - - 



100 



4 



100 



4 ... 



100 



2 - _- --- - 



100 



2 - 



100 



1 



66.2 



1 



34.7 











In this table several significant points can be noted. Some normal 

 grubs were found in the tests with 1 ounce for 90 minutes, whereas 

 with 1 ounce for 120 minutes no normal but some sick grubs were 

 found. With 2 ounces a complete kill was obtained with exposures 

 of 90 and 120 minutes. With 4 ounces a complete kill resulted from 

 exposures of 30 minutes or longer. Reference to table 3 shows that 

 these results confirm those with compounds nos. 3 and 4, although 

 the tests with those materials were conducted at 80° F. 



REACTION OF ADULT BEETLES TO LIQUID HYDROCYANIC ACID 



As soon as adult beetles were available, a series of three tests were 

 conducted in the fumigating house with liquid hydrocyanic acid. 

 In each test 1,000 beetles were exposed to 2 ounces of the chemical 

 per 1,000 cubic feet of space, for 2 hours, at temperatures of 76°, 71° 

 and 66-71° F., respectively. In the third test the initial temperature 

 of 66° was obtained by placing several large cakes of ice in the fumi- 



