5 



jected to the action of the gas. The fumigation of orchard trees 

 or garden plants with hydrocyanic acid gas requires a covering 

 for the plants to retain the gas. These are usually made in the 

 form of a tent of stout canvas soaked in oil or cactus juice, or in 

 the form of a box, the frame of which is covered with cloth sim- 

 ilarly saturated with oil. Seeds, plant stocks, furniture, and 

 other material can be most economically fumigated in an air- 

 tight receptacle or compartment of suitable dimensions, and if 

 much fumigation is to be done, a fumigating box or house should 

 be specially constructed with the idea of convenience in placing 

 the "charge," storing the material, and ventilation. Mills, ware- 

 houses and storerooms can usually be fumigated when infested 

 by covering windows and doors and stopping up cracks and other 

 sources of leakage with paper pastings. 



To generate hydrocyanic acid gas, cyanide of potassimn, sul- 

 phuric acid and water are used in the proportions of 1 ounce of 

 cyanide to 1 fluid once of acid and 3 of water. An earthenware 

 vessel should be used. First pour in the water, then the acid, 

 and do not add the cyanide until everything is ready for the gen- 

 eration of the gas. For general purposes, use 1 ounce of cyanide 

 with the proper amount of acid and water, -peT 100 cubic feet. 

 The gas is lighter than air and diffuses rapidly, so that ample 

 allowance must be made for leakage. 



The fumes of carbon bisulphid are better than hydrocyanic 

 acid gas for some purposes. They are heavier than air and far 

 more penetrating. The liquid also is much more easily handled. 

 It is therefore preferable for fumigating small lots, for grain 

 and seeds, which usually pack closely, and for use about houses. 

 It is also useful for ground-inhabiting insects, root-maggots and 

 root worms, root-feeding aphids, ants, borers, &c. In air-tight 

 compartments it is used at the rate of 1 pound per 1,000 cubic 

 feet. For ants, a teaspoonful poured into the opening of the nest 

 will usually destroy all the ants in the nest. For root forms, 

 5 ounces per plant are necessary, and usually several successive 

 applications. 



