USE OF GASES AGAINST HOUSEHOLD INSECTS 445 



per pound retail in small quantities. In large quantities 

 it should be purchased for much less. 



The crude form of sulfuric acid may be used. It is a 

 thickish brown liquid and should test about 1.84 sp. gr. or 

 66° Beaume. It should not cost more than four or five 

 cents a pound. If a room is made tight, one ounce of 

 the cyanide for every one hundred cubic feet of space has 

 been shown to be sufficient. In cases of loosely con- 

 structed buildings that cannot be tightly calked double 

 this amount may be used. The ingredients (Fig. 151) are 

 combined in the following proportions : — 



Potassium cyanide 1 ounce 



Commercial sulfuric acid 1 fluid ounce 



Water 3 fluid ounces 



Method of procedure. — It will be simpler to take a 

 single room as an example. Suppose the room to be 12 by 

 15 by 8 feet. It will contain 12 X 15 X 8, or 1440 cubic 

 feet. For convenience, the writer always works on the 

 basis of complete hundreds, and in this case he would 

 work on the basis of 1500 cubic feet, preferring to err on 

 the side of too much than too little. The room, then, would 

 require 15 ounces of cyanide, 15 ounces of sulfuric acid, 

 and 45 ounces of water. 



First of all, the room should be made as tight as possible 

 by stopping all the larger openings, like fireplaces and 

 chimney flues, with old rags or blankets. Cracks about 

 windows or in other places should be sealed with narrow 

 strips of newspaper thoroughly soaked in water. Strips 

 of newspaper two or three inches wide, that have been 

 thoroughly wet may be applied quickly and effect- 

 ivelv over the cracks around the window sash and 



