83 



of potassium for any purpose, and if it be found practicable to treat 

 buildings in general for the extermination of insects the work should 

 be done under the direction of competent officials. Our experiments 

 have shown that a smaller dose and a shorter period of exposure are 

 reauired to kill mice than for roaches and household insects gener- 

 ally^, and it readily follows that the larger animals and human beings 

 would be more quickly overcome than mice, since a smaller supply of 

 pure air would be required to sustain life in mice, and small openings 

 are more numerous than large ones. 



The materials emplo3^ed and the method of procedure are as follows : 

 After ascertaining the cubic contents of the inclosure, provide a glass 

 or stone ware (not metal) vessel of 2 to 4 gallons capacit}^ for each 

 5,000 cubic feet of space to be fumigated. Distribute the jars accord- 

 ing to the space and run a smooth cord from each jar to a common 

 point near an outside door where they may all be fastened ; support the 

 cord above the jar b}^ means of the back of a chair or other convenient 

 object in such a position that when the load of cyanide of potassium is 

 attached it will hang directl}^ over the center of the jar. Next weigh 

 out upon apiece of soft paper 500 grams (about 17.1 ounces) of 98 

 per cent pure cyanide of potassium, using a large pair of forceps for 

 handling the lumps, wrap up and place in a paper bag, and tie to the 

 end of the cord over the jar. After the load for each jar has been 

 similarl}^ provided, it is well to test the working of the cords to see 

 that they do not catch or bind. Then remove the jar a short distance 

 from under the load of cyanide and place in it a little more than a 

 quart of water, to which slowly add 1| pints of commercial sulphuric 

 acid, stirring freely. The action of the acid will bring the tempera- 

 ture of the combination almost to the boiling point. Replace the jars 

 beneath the bags of cyanide, spreading a large sheet of heavy paper 

 on the floor to catch any acid that may jiossibly fly over the edge of 

 the jar when the cyanide is dropped, or as a result of the violent 

 chemical action which follows. Close all outside openings and open 

 up the interior of the apartment as much as possible in order that the 

 full strength of the gas may reach the hiding places of the insects. 

 See that all entrances are locked or guarded on the outside to prevent 

 persons entering, then leave the building, releasing the cords as you 

 go. The gas will all be given off in a few minutes and should remain 

 in the building at least three hours. 



When the sulphuric acid comes in contact with the cyanide of 

 Ijotassium the result is the formation of sulphate of potash, which 

 remains in the jar, and the hydrocyanic acid is liberated and escapes 

 into the air. The chemical action is so violent as to cause a sputter- 

 ing, and frequently particles of the acid are thrown over the sides of 

 the jar. This may be prevented by sup]3orting a sheet of stiff paper 

 over the jar by means of a hole in the center, through which the cord 

 supporting the cyanide of potassium is passed, so that when the cord 



