HYDROCYANIC ACID FUMIGATION 



385 



steamlike gas arises. If preferred, however, the paper bag may 

 be suspended by a string passing through a screw eye in the 

 ceiling and through the key hole of the door (Fig. 170). The 

 operator may then lower the bag into the jar after leaving the 

 room. When stringing a room in this manner, care should be 

 taken not to place the acid jar under the bag until everything is 

 ready. The fumigation should extend over a period of five or 

 six hours at least, a good method being to start the operation 

 toward evening and let it run 

 all night. Better results will 

 be obtained at a temperature 

 of 70° F. or above, than at 

 a lower temperature. 



Two or three hours after 

 the doors and windows have 

 been opened the gas will have 

 disappeared sufficiently to 

 allow safe entrance into the 



,1 u 'J- u ij J. Fig. 170. A room "strung" for hydro- 



room, though it should not <,y^„i„ ^.ij g^, fumigation from outside. 



be occupied until the char- The bag of cyanide can be lowered into the 

 , • , . 1 . rrni crock of sulphuric acid and water by means 



acteristlC odor is gone. The „f t^e string. (After Herrick.) 



contents of the generating 



jar should be dumped in some safe place and the jar washed 

 before being used again. When a whole house is to be fumigated 

 each room should be made ready as described above and then 

 set off in regular order beginning on the upper floor and working 

 downward, since the gas is lighter than air and therefore rises. 

 Herrick describes clearly and in detail the method which he 

 has successfully used in the fumigation of large dormitories. 

 For this account the reader is referred to Herrick's " Insects 

 Injurious to the Household," pages 448 to 452. 



The effectiveness of this method of fumigation against bedbugs 

 was proven by experiments conducted by Herrick. Bugs were 

 placed in perforated pill boxes and wrapped in various manners, 

 some with three inches of excelsior, some in two folds of a thick 

 comforter, some in two inches of cotton batting and others in two 

 folds of a woolen blanket. Others were placed in a cork stop- 

 pered vial, the cork of which was punched twice with a pair of 

 curved forceps. In each box several newly laid eggs were en- 

 closed to determine the effect of the gas on their hatching. In 



