HOUSEHOLD AND CAMP INSECTS 75 



phuric acid and their derivative, hydrocyanic acid gas, are among 

 our most active and deadly poisons. They should be handled with 

 extreme care and every precaution taken to avoid an accident, since 

 a slight mistake may result in one or more fatahties. 



One ounce of high-grade 98 per cent cyanide of potassium and 

 one fluid ounce of the 'best commercial sulphuric acid diluted with 

 2 fluid ounces of water should be used for every 100 cubic feet 

 of space. Pure sodium cyanide produces one-third more hydro- 

 cyanic acid gas to a pound than does the cyanide of potassium and 

 is a very satisfactory substitute. If this be used instead of the 

 potassium cyanide, i^ ounces of sulphuric acid and 3 ounces of 

 water are advised for each ounce of the poison. Its slightly greater 

 cost is balanced by the larger amount of gas. Sodium cyanide is 

 now being manufactured in special one ounce molds for fumigation 

 purposes. The amounts recommended above should be doubled for 

 poorly constructed houses. The fumigation should last at least 

 30 minutes and it would be preferable to have it continued 3 or 4 

 hours, or if convenient, all night. 



Rats and mice are also killed by this treatment and it is fortunate 

 that these animals rush out into the open before succumbing, so 

 that there is little or no danger of subsequent annoyance due to 

 dead animals in the walls or under the flooring. 



Prior to treatment all fluids, especially liquid or moist foods, 

 should be removed from the house. Arrangements should be made 

 to open the building from the outside after the fumigation is com- 

 pleted. Windows and doors should be sealed as tightly as possible, 

 either by stuffing damp paper in the crevices or pasting strips of 

 paper over cracks. Chimney places, ventilators and other orifices 

 should be closed tightly. The gas is generated by dropping the 

 cyanide of potassium, previously broken into lumps about the size 

 of a walnut and preferably placed in thin bags or wrapped loosely 

 in thin paper, into the requisite amount of diluted acid. The acid 

 should be carefully diluted by pouring it slowly, accompanied by fre- 

 quent stirring, into the necessary amount of water. This dilution 

 should be slow enough to avoid all danger of this very strong acid 

 splashing and perhaps causing dangerous burns. It will be found 

 advisable to have one or more jars or generators in each room or 

 hallway, since it is not wise to use more than 2 pounds of cyanide 

 in a generator. The large, preferably deep, earthenware vessels 

 used as generators should be placed near the middle of the room and 

 on a thick layer of newspapers in order to avoid possible injury 



