150 FUMIGATION METHODS 



acid was then dropped in and the door quickly closed. 

 The vials were dropped in with the mouths down, and 

 the contents drained out gradually, avoiding a puff of 

 the gas by too rapid generation. The box was kept 

 closed for ten minutes, or as long as desired. Both 

 doors were then thrown open and the trays lifted out, 

 so that the plants were thoroughly aired. 



The cyanide solution should be secured from a 

 druggist, put up in homeopathic vials, one dose in each 

 vial. The solution consists of* 100 grammes 98 per cent, 

 potassium cyanide dissolved in water to make 200 

 cubic centimeters solution. The amount necessary for 1 

 each dose is easily computed: multiplying the cubic 

 contents of the box by 0.4 will give the number of 

 cubic centimeters of the solution to be used, this giving 

 a strength of o. 2 gramme potassium cyanide per cubic 

 foot. Use an equal amount of sulphuric acid, which 

 can be readily measured into empty vials. Thus for a 

 box 2 x 2 x 2^ feet, or 10 cubic feet, 4 cubic centi- 

 meters of the solution, or a two- drachm vial half full, 

 and an equal amount of sulphuric acid (best grade 

 commercial, 1.85 specific gravity) would be used for 

 a strength of 0.2 gramme potassium cyanide per cubic 

 foot, or the same vial three-quarters full for a strength 

 of 0.3 gramme potassium cyanide per cubic foot. 



Small plants in the field. For individual plants, 

 such as melon, cucumber, cabbage, etc. , a small cover 

 is needed. In many cases where only a few plants are 

 to be treated, a two-gallon wooden pail or other simi- 

 lar vessel will do. Paper or canvas covered boxes, one 

 or two feet square at the base, and fifteen to twenty 

 inches high, can be made cheaply and used to good 



