92 BIOLOGY AND TECHNIQUE 



lets of paraform and unslaked lime are together laid into a pan and 

 warm water is poured over them. 



A very simple method is the potassium permanganate method of 

 Evans and Russell. 1 This method depends upon the active reaction oc- 

 curring when formalin and potassium permanganate are mixed. Per- 

 manganate is placed into a bucket and the formalin poured over it. The 

 bucket should be large enough to prevent overflowing when the mixture 

 foams. Special galvanized iron pails are made with funnel-shaped tops, 

 and pails should be placed on a piece of iron sheeting or bricks to prevent 

 overheating of the floor; 500 c.c. of commercial formalin and 250 grams 

 of potassium manganate should be used for every 1,000 cu. ft. 



The room in which formaldehyd has been liberated is kept sealed, in 

 the manner already described, for at least twelve hours, after which the 

 windows and doors are opened. The odor which remains after formalde- 

 hyd fumigation may be removed by sprinkling with ammonia, or by 

 the use of some one or another of the various sorts of apparatus de- 

 vised for the liberation of ammonia. 



For the destruction of rodents, hydrocyanic acid gas is used in the 

 fumigation of ships and houses. This is of especial importance in con- 

 trolling such diseases as plague. Recently Creel, Faget, and Wrightson, 

 of the United States Public Health Service, have studied this method. 

 They found hydrocyanic acid gas is more penetrating, more toxic, and 

 more easily applied than either sulphur dioxid or carbon monoxid. 5 oz. 

 of powdered potassium cyanid per 1,000 cu. ft. of space was sufficient to 

 kill rodents. The gas is produced by dropping the potassium cyanid into 

 sulphuric acid of a specific gravity of 1.84, or commercial grade 66B. 

 The gas is as effective for insects as it is for rodents. The element of 

 danger to human life must be always considered in carrying out such 

 fumigation, but the writers referred to believe that there is no danger 

 to men entering a place fumigated in this way 30 minutes or longer after 

 the apertures have been opened. For the fumigation of the hold of a 

 ship, Creel, Faget, and Wrightson 2 use an ordinary wooden barrel, into 

 the top of which is placed a large galvanized iron funnel. The cyanid, in 

 5-gal. tins with top removed, may be attached to the funnel and dumped 

 into the sulphuric acid by means of a rope attached to the tin, after the 

 barrel has been lowered. 



1 Evans and Russell, Rep. State Bd. Health, Maine, 1904. 



2 Creel, Faget, and Wrightson, United States Public Health Reports, Vol. 30, No. 

 39, Dec. 3, 1915. 



