B. C. ENTOMOLOGICAL PROCEEDINGS, 1912. 29 



For this work Hydrocyanic Acid Gas, for nursery stock, trees and 

 shrubs, and Carbon Bisulphide for grain, roots and bulbs, etc., are 

 almost universally used. The action of these two gases accounts for 

 their separate uses. 



The Hydrocyanic Acid Gas is lighter than air and works upwards. 

 It is generated by placing Cyanide Potassium into an earthen jar con- 

 taining Sulphuric Acid and water. It is one of the deadliest gases 

 known, and poisons the lungs instantly. Owing to its rapid action, the 

 nursery stock is quickly treated and does not have to remain exposed 

 to the fumes long enough to do it injury. 



There are certain insects, such as Spiders, Root Borers, some Moth 

 Larvae, Aphis, etc., that are immune to the short exposure and are cap- 

 able of withstanding the gas longer than might be good for some of 

 the nursery stock. 



Carbon Bisulphide Gas is heavier than air and works downwards. 

 It is a colorless liquid, resembling water, and is formed by the union 

 of two elementary particles of sulphur with one of carbon. (The 

 chemical symbol is CS.) The commercial Carbon Bisulphide is now 

 made on a large scale by a new electric process. 



The fumes of burning sulphur are passed over red-hot charcoal 

 and the resulting vapors are condensed to a liquid by cooling. This 

 liquid gas is one-fourth heavier than water. Its specific gravity is 1.29 

 at the freezing temperature of water. The gas is generated by coming 

 in contact with the atmosphere, and is 2.63 times heavier than air. 

 For this reason, it is peculiarly adapted for the fumigation of solid 

 masses of grain, roots or soil. 



There are hundreds of tons of imported rice and grain treated 

 at the Vancouver and Victoria Fumigating Stations eacli year, and the 

 process is as follows: 



The sacks containing the rice or grain are stacked two or four 

 deep on the floor of the fumigation chamber. Soup plates are placed 

 at equal distances on top of the sacks, all windows and doors are sealed, 

 and the amount of liquid Carbon Bisulphide necessary to the cubic 

 space measurement of the chamber is distributed in equal quantities in 

 each soup plate. The chamber is then closed and sealed for thirty-six 

 hours. 



During the process of distributing the liquid in tlie plates, one 

 naturally becomes acquainted with some of the peculiar effects of the 

 gas, which commences to generate directly it is poured out. 



The operator does not experience any disagreeable sensation, and 

 has no desire to leave the chamber, but after a few minutes he may 



