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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 
required 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 larze ones. 
The materials employed 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 capacity for each 
5,000 cubie 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 by 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 directly 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 
similarly 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 13 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 fioor to catch any acid that may possibly 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 
potassium the result is the formation of sulphate of potash, which 
remains in the jar, and the hydrocyanie 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 supporting 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 
