12 



CIRCULAR 369. U. S. DEPT. OF AGRICULTURE 



1 and 12) or some similar container (fig. 13). This method, while 

 more laborious than others, gives excellent results and is the safest 

 for the nse of other than professional fnmigators. It can be made 

 the cheapest method of fumigation. 



Chemicals Requiked 



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

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



materials required. 



Sodium cyanicte is a 

 white crystalline sub- 

 stance, which for fu- 

 migation purposes is 

 prepared in egg- 

 shaped lumps weigh- 

 ing approximately to 

 to 1 ounce each. It 

 is a violent stomach 

 poison, and can also 

 cause serious poison- 

 ing by being ab- 

 sorbed through open 

 cuts on the hands. 

 For this reason it is 

 best handled with a 

 scoop or shovel or 

 with gloved h a n d s 

 (fig. 14). It can be 

 purchased in 100- 

 pound lots for from 

 16 to 22 cents per 

 pound, and in smaller 

 lots at a proportion- 

 ally higher price. 



Pure sulphuric 

 acid is a heavy, col- 

 orless liquid, but the 

 commercial acid used 

 in large-scale fumiga- 

 tion 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-gallon carboys for about 

 4 cents per pound. "When large quantities of acid are required, a 

 tilting frame will be found convenient in pouring the acid from the 

 carbon's. Workmen should learn to pour acid slowly and with cau- 

 tion (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 



Figure 13. — Crock for the generation of hydrocyanic acid 

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

 to prevent injury to floors in case the crock crack?. 



