58 BULLETIN 137, U. S. DEPARTMENT OF AGRICULTURE. 



enameled dipper has been found convenient in placing the cyanid 

 in the generators. The reaction of the chemicals is extremely rapid, 

 and the generation of the deadly gas begins at once. In fumigating 

 large buildings, where a considerable number of generators are re- 

 quired, the operator should have several assistants. In such cases 

 it is best to have the proper amount of cyanid in paper sacks placed 

 beside the jars holding the acid and water. Begin dropping the 

 cyanid in the jars farthest from the door first, going from one jar 

 to the next as rapidly as possible. 



TEMPERATURES FAVORABLE FOR EFFECTIVE FUMIGATION. 



In using fumigants for the control of the tobacco beetle, best re-" 

 suits have been secured in warm weather and at temperatures above 

 70° F. Under 60° or 65° F. the beetles are more or less dormant 

 and while in this condition are considerably more resistant to the 

 action of the gas. 



DOSAGES TO USEa. 



Sodium cyanid (NaCn). — This substance when pure liberates 

 nearly one-third more hydrocyanic-acid gas per pound than does 

 potassium cyanid and at present it is more generally used for fumi- 

 gation. 



Sodium cyanid should be combined with acid and water to gen- 

 erate the Ivydrocyanic-acid gas according to the following formula: 



Sodium cyanid (grade guaranteed to contain not less than 



51 per cent cyanogen) avoirdupois ounce 1 



Sulphuric acid (commercial) fluid ounces 1% 



Water fluid ounces 3 



Use multiples of the formula given above to secure the dosage 

 desired. Fumigate for 24 hours. The dosage to use will depend upon 

 the penetration required. For general use 4 ounces of the cyanid 

 to 100 cubic feet will be found satisfactory. (This dosage requires 

 4 ounces of the cyanid, 6 fluid ounces of acid, and 12 fluid ounces of 

 water.) For baled or closely packed tobaccos a somewhat heavier 

 dosage may be used, or the time of exposure increased. An increase 

 of the amount of cyanid above 4 ounces per 100 cubic feet, however, 

 has not greatly increased the effectiveness of the treatment in many 

 instances. 



• Potassium cyanid. — Should potassium cyanid be used in place of 

 the sodium cyanid, it should be combined with the sulphuric acid 

 and water according to the following formula : 



Potassium cyanid (98-99 per cent) avoirdupois ounce__ 1 



Sulphuric acid (commercial) fluid ounce — 1 



\Ynr<>r fluid ounces — 3 





