CONTROL OF HOUSEHOLD INSECTS 43 



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, accom- 

 panied by frequent 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 two 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 news- 

 papers in order to avoid possible injury from splashing acid. Pre- 

 cautions should be observed, if the building is in contact with 

 others in a row, to see that parties in adjacent dwellings are warned 

 and arrangements made so that the rooms next the treated building 

 will be kept well aired during the fumigation. It is unsafe to 

 attempt to fumigate individual rooms in a house or a building in 

 a row, unless one can be certain that there will be good aeration 

 on all sides of the apartment or building. The deadly character 

 of this gas is shown by the destruction of sparrows resting upon 

 the eaves of a building during fumigation. One should not attempt 

 to fumigate a building or a room alone, because an accident under 

 such conditions is very likely to result fatally. Since hydrocyanic 

 acid gas is lighter than air, operations should commence at the 

 top of the building and proceed successively from floor to floor. 

 Better still, place the requisite amount of the cyanide of potassium 

 in thin bags, suspend each over its generator in such a manner 

 that when a string near the exit is loosened, all will drop into the 

 jars. The poison should not be in a thick paper bag, as the action 

 of the acid may be seriously hindered if not almost prevented. 



Under no conditions should any one be allowed to enter the 

 building prior to the completion of the fumigation and its thorough 

 aeration. At least 30 minutes and preferably an hour or more, 

 depending somewhat upon the means of A T entilation, should be 

 allowed for this latter process. It is unsafe to enter any recently 

 fumigated building until all the odor of the gas, resembling that of 

 peach kernels, has disappeared. The contents of the fumigating 

 jars should be carefully disposed of together with any remaining 

 cyanide. These substances can either be buried deeply in the 

 soil, or if in a city, may be poured into the sewer. 



