12 



CIRCULAR 3 69, U. S. DEPARTMENT OF AGRICULTURE 



Chemicals Required 



Sodium cyanide (96 to 98 percent, containing 54 percent HON), a 

 commercial grade of sulphuric acid (66° B.), and water are the only 

 materials required. Sodium cyanide is a white crystalline substance, 

 which for fumigation purposes is prepared in egg-shaped lumps 



weighing approxi- 

 mately y 2 to 1 ounce 

 each. It is a violent 

 stomach poison, and 

 can also cause seri- 

 ous poisoning by be- 

 ing absorbed through 

 open cuts on the 

 hands. For this rea- 

 son it is best handled 

 with a scoop or 

 shovel or with gloved 

 hands (fig. 14). It 

 can be purchased in 

 100-pound lots for 

 from 16 to 22 cents 

 per pound, and in 

 smaller lots at a 

 proportionally high- 

 er price. 



Pure sulphuric 

 acid is a heavy, 

 colorless liquid, but 

 the commercial acid 

 used in large-scale 

 fumigation work is 

 slightly discolored, 

 or murky, owing to 

 impurities. It is 

 highly corrosive and 

 will cause injury if 

 it is spattered on the 

 clothing or body of 

 the operator or upon 

 the floor. It can be 

 purchased in 11 -gal- 

 lon carboys for about 

 1 cents per pound. 

 When large quan- 

 tities of acid are required, a tilting frame will be found convenient 

 in pouring the acid from the carboys.Workmen should learn to 

 pour acid slowly and with caution (fig. 15), 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. 



Figuee 13. — Crock for the generation of hydrocyanic acid 

 gas by the pot method, set in small galvanized-iron tub 

 to prevent injury to floors in case the crock cracks. 



