18 



The Philippine Journal of Science 



191< 



If it is desired to insure complete fumigation of a compartment 

 of the dimensions described under "Fumigation" containing 32.4 

 cubic meters, then the following quantities should be used : 



Potassium cyanide, 98 per cent 1 kilogram. 



Sulphuric acid, commercial, 93 per cent 1 liter. 

 Water 2 liters. 



If a greater proportion of water is used than described, the 

 yield of gas is decreased by about 4 per cent for each additional 

 liter until 7 liters of water are used, when the yield of gas begins 

 to drop off even more rapidly as shown by Table IX : 



Table IX. 



-Percentage of available hydrocyanic-acid gas given off when 

 different quantities of water are used. 



Relative proportion by weight 

 of— 



Proportion 



of available 



gas given 



off. 



Potassium 

 cyanide. 



Acid. 



Water. 



1 

 - 



'■ 



1 



2 

 3 



4 



e 



6 



7 

 8 



Per cent. 

 87.84 

 93.76 

 89.95 

 86.25 

 81.68 

 79.65 

 73.47 

 43.27 



Potassium cyanide can be obtained at any drug store or pur- 

 chased in large quantities in Germany and in the United States ; 

 98 per cent pure sells for 1.29 pesos per kilogram, delivered 

 in Manila. 



DIRECTIONS FOR FUMIGATING WITH HYDROCYANIC-ACID GAS 



The compartment should always be filled to its full capacity 

 with tobacco when fumigating. Hydrocyanic-acid gas is lighter 

 than air and should be liberated at the bottom of the compart- 

 ment. Earthenware jars should always be used for generators; 

 sulphuric acid attacks metal, and glass is too fragile. When 

 all is ready, mix the water and sulphuric acid in the generator, 

 always by pouring the acid into the water; then, while the 

 solution is still hot, add the cyanide. Better results are obtained 

 with a hot solution. Never reverse the order of mixing. When 



