14 CIRCULAR 3 6 9, U. S. DEPARTMENT OF AGRICULTURE • 



will be found convenient in pouring the acid from the carboys. Work- 

 men should learn to pour acid slowly and with caution, for their 

 clothing or shoes will be damaged if a drop of acid falls on them. It 

 is well to have easily accessible a pail of water in which some washing 

 soda has been dissolved, for quickly washing away droplets of acid 

 that may spatter on face, hands, or clothing. A sulfuric acid pump 

 that can be attached to a carboy is somewhat slower but easier to 

 handle. 



All men handling the dry sodium cyanide and mixing the acid 

 and water should wear oiled gloves and tight-fitting goggles. The 

 workers who place the bags of sodium cyanide in the acid and 

 water mixture should also wear gas masks equipped with the 

 proper canister for this gas. 



For best results the chemicals should be mixed according to the 

 following formula : 3 



Sodium cyanide pound— 1 



Sulfuric acid pints iy 2 



Water do 3 



Proper Order of Placing Chemicals in Generator 



To generate hydrocyanic acid gas by this method, the operator 

 should first pour the water into the generator and then add the acid. 

 If the procedure is reversed, the reaction is so violent that the oper- 

 ator may be dangerously burned by the spattering of the acid-water 

 mixture. The sodium cyanide is not added to the mixture of water 

 and acid until everything is in readiness for the fumigation, as it 

 causes an immediate chemical reaction in which hydrocyanic acid 

 gas is given off (fig. 14). The pure gas is colorless, but when mixed 

 with steam produced by the chemical reaction it has the appearance 

 of a light bluish smoke. It has an odor resembling that of peach 

 kernels. 



Dosage 



The dosage is computed on the basis of the quantity of sodium 

 cyanide required. For general mill or factory fumigation where no 

 large quantities of materials are stored, 1 pound of sodium cyanide 

 will produce enough gas to fumigate 1.000 cubic feet of space, if 

 the building is of reasonably tight construction. If the building to 

 be fumigated is filled with merchandise, the dosage required will 

 vary according to the nature of the merchandise. Dosages have been 

 computed for the fumigation of the more important commodities and 

 will be discussed hi a later section of this circular. 



THE GENERATOR 



For large-scale fumigations a water-tight 50-gallon wooden oil 

 barrel (figs. 1, 12, and 14) is the most suitable generator to use. 

 Metal barrels are not satisfactory. Barrels in which paint, glue, 

 molasses, pitch, etc., have been stored should be avoided, for when the 

 acid is added it may eat out these materials from between the staves, 

 thus causing a barrel thought to be liquid-tight to leak. Barrels 



3 Chemical tests indicate that a 1—1 %-2 formula yields more gas than the 1—1 %-3 

 formula here recommended. The smaller quantity of water often results in a crystalliza- 

 tion of the residue which makes the emptying of the containers after fumigation more 

 difficult. In general large-scale work the authors have found the 1—1 %-3 formula more 

 practical and the results satisfactory. 



