384 BEDBUGS AND THEIR ALLIES 



poisonous not only to insects but also to other animals and to man, 

 its use must be accompanied by great care and precaution. A 

 few deep breaths of the gas is sufficient to cause asphyxiation. 

 On the other hand it has great advantages in that it is not in- 

 flammable or explosive, and, unlike sulphuric fumes, does no 

 damage to dry foods or to household goods, except to tarnish 

 nickel slightl3^ Wet foods may absorb some of the gas and 

 should be removed before fumigation. Care should also be 

 taken that there is no possible avenue of escape for the gas into 

 adjoining rooms or houses which are occupied. The character- 

 istic peach-kernel odor, however, makes its detection easy, thus 

 removing danger of asphyxiation without warning. 



The gas is generated by the action of sulphuric acid on potas- 

 sium cyanide. The procedure as advised by Herrick is as fol- 

 lows: Estimate the number of cubic feet in the room or house 

 to be fumigated, and allow one ounce of potassium cyanide to 

 every 100 cubic feet. Make the room or house as near air tight 

 as possible, stopping all the large openings such as fireplaces and 

 chimney flues with old rags or blankets. Seal cracks about win- 

 dows and doors with strips of wet newspaper. Such strips when 

 thoroughly wet can be applied quickly and effectively over cracks 

 and will stick tightly for several hours, and can be removed easily 

 after the operation. While the room is being made tight some- 

 one should measure out the required ingredients for fumigation, 

 allowing one fluid ounce of crude sulphuric acid and three fluid 

 ounces of water to each ounce of potassium cyanide. The water 

 first should be poured into a stone crock holding two gallons or 

 more, i.e., large enough so that the reacting fluid will not spatter 

 on floors or carpets. The crock had best be placed on several 

 thicknesses of newspaper or on an old rug or burlap sack. The 

 required amount of sulphuric acid should then be poured slowly 

 into the water. Never pour the water into the acid. The cyan- 

 ide should be weighed out and put into a paper bag beside the 

 jar. All articles which might suffer from the gas or which will 

 be needed before the operation is over should be removed from 

 the room. When everything is ready the operator, holding his 

 breath, should drop the paper bag of cyanide gently into the 

 acid jar, and walk out shutting the door behind him. The time 

 required for the acid to eat through the paper bag in order to 

 reach the cyanide gives ample time to leave the room before the 



