28o CONNECTICUT EXPERIMENT STATION REPORT, I907-I908. 



Hydrocyanic Acid Gas. 



Hydrocyanic acid is a colorless gas (HCN) and one of the 

 most poisonous gases known. It has the odor and taste of 

 prussic acid or bitter almonds. It is lighter than air, and is 

 generated by adding water and sulphuric acid to potassium 

 cyanide in about the following proportions : 



Potassium cyanide I ounce 



Sulphuric acid 2 fluid ounces 



Water 4 " 



The quantities named have been determined by experiment to 

 be suitable for one hundred cubic feet of space in fumigfating 

 dormant nursery trees. As potassium cyanide is often adulter- 

 ated with sodium cyanide or with common salt (sodium 

 chloride), only the best grade (98-99 per cent.) and the best 

 commercial sulphuric acid should be used. The value of the tests 

 with this gas is for purposes of comparison, and yet it also 

 shows that nursery stock is not injured by it when properly 

 fumigated. The results are given in Table V. 



Results with Hydrocyanic Acid Gas. 



All scales were destroyed and no trees were, injured except 

 in two lots one from each died, but there is no indication that 

 they were killed by the gas. One point to be noted is that in 

 Experiment No. 30 the trees were given the same quantity of 

 cyanide commonly used for fumigating nursery stock (one ounce 

 per 100 cubic feet) and twice the period. The trees were 

 sprinkled thoroughly by means of a watering pot, — ^but none 

 were injured by this fumigation. It should also be noted that 

 twice the usual quantity for four times the usual period, and 

 that three times the usual quantity for one-half hour (the usual 

 period) caused no injury to the trees. 



General Remarks. 



These tests are preliminary and conclusions based upon them 

 are scarcely warranted. Yet they indicate the desirability of 

 making further tests with smaller quantities of carbon tetra- 

 chloride and with longer fumigating periods with the small 

 amounts of carbon disulphide. Possibly it will appear that one 

 or both of these liquids are suited for fumigating small lots 



