18 BULLETIN 872, U. S. DEPARTMENT OF AGRICULTURE. 



Proportion of Chemicals. 



Hydrocyanic-acid gas is generated by mixing in proper proportion 

 sodium cyanid, sulphuric acid, and water. These should be com- 

 bined as follows : 



1 ounce, by weight, of sodium cyanid. 



1J ounces, liquid measure, of sulphuric acid. 



2 ounces, liquid measure, of water. 



This is known as the 1-1^-2 formula. Slightly varying formulas 

 have been recommended, but this 1-1J-2 formula yields good results. 



Equipment for Generating Gas. 



The equipment for generating gas may be very simple and should 

 include the following : 



Containers for generating the gas. — For mill fumigation, 4-gallon 

 earthenware stone crocks, well glazed, such as may be purchased at 

 any hardware store, have proved very satisfactory. Four-gallon 

 crocks (see figs. 8 to 14) will receive a charge containing a maxi- 

 mum of 4 pounds of cyanid. Fumigation does not injure them for 

 other purposes provided they are properly cleaned. Where very 

 large spaces are to be fumigated strong water-tight wooden barrels 

 have frequently been used. Untreated oil barrels in good condition 

 have served for several fumigations without marked deterioration, 

 where care is taken to add the acid slowly and to rinse thoroughly 

 after using. A 50-gallon barrel will accommodate with ease a charge 

 of 20 to 30 pounds. Containers holding larger quantities of solution 

 are more difficult to remove and empty than smaller ones, and this is 

 an important item. Good barrels sufficiently small to fit easily into 

 an ordinary galvanized-iron washtub (fig. 7) and receive charges 

 of 15 to 30 pounds of cyanid are very satisfactory when buildings 

 are so arranged that they can be easily removed and emptied. If 

 the tubs are partly filled with water to which have been added sev- 

 eral handf uls of ordinary salsoda, there is no danger that the acid 

 will spill out onto the floor during the chemical reaction which pro- 

 duces the gas, and the handles of the tub make it easy for two men 

 to remove the tub and barrel at the same time after fumigation. 



Measuring and carrying equipment. — Scales are needed for weigh- 

 ing cyanid. Glass graduates of 16 or 32 ounce capacity should be 

 used for measuring acid and water. One or two gallon granite ware 

 cups and pitchers are very convenient and safe for carrying acid. 

 Ordinary granite ware buckets in good condition can be used 

 very satisfactorily in carrying acid from carboys to generators, 

 though these should be carefully washed immediately after use and 

 not allowed to stand with acid in them. Containers of tin must 

 not be used. 



