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similarly closed. All outlets to the room—ventilators, registers, 
pipe openings, and the like, as well as cracks in the floors, ceilings, 
and walls—should be stuffed with waste and covered with paper. 
As carpenters' glue is difficult to remove, a good flour paste may 
he substituted for it where this is a matter of importance. 
Hydrocyanic acid gas is produced by the reaction of cyanide of 
potassium, sulphuric acid, and water, the gas coming off with a 
more or less violent bubbling of the mingled fluids. The gas 
evolved is one of the most prompt and powerful poisons in com¬ 
mon use, and the residue left after the reaction is sufficiently poison¬ 
ous to make it necessary that it should be carefully disposed of 
by burying. The cyanide used should be in lumps, and 98 percent 
pure. To insure this strength a reliable brand should be bought 
in its original sealed package. That manufactured by Merck & 
Company, of New York, is of standard quality and can be de¬ 
pended on. Commercial sulphuric acid is of sufficient purity, but 
it should have a specific gravity of about 1.83 (66° Beaume). 
Cyanide should be protected from moisture and kept in sealed ves¬ 
sels, as it is otherwise liable to decompose. Gloves should be worn 
while handling either of these chemicals. 
To determine the amount of the ingredients needed for fumiga¬ 
tion, one must first find the cubic contents of the containing room, 
making no allowances for furniture or other objects in it. An 
ounce, by weight, of cyanide, and a fluid ounce of commercial acid 
are needed for every hundred cubic feet of space in the room. 
Three-gallon earthenware jars make suitable generators, and 
these should be provided at the rate of one for every five thousand 
cubic feet of space to be fumigated. As, for the best effect, the 
gas must be held at least eighteen hours, the importance of tight 
construction is manifest. If, however, this is impracticable, the 
strength of the gas—the amount, that is, of the ingredients per 
hundred cubic feet—must be increased according to the judgment 
of the operator. In some cases even twice the above quantities 
may be found necessary to a successful operation. 
The containers should then be distributed thruout the room or 
rooms and the proper amount of water should be poured into each. 
The sulphuric acid should next be measured out and gently poured 
into the water. The cyanide of potash should be prepared for use 
by breaking it into lumps somewhat smaller than an egg. This 
should be done in the open air. It should then be carefully weighed 
out and placed in thin paper bags in quantity sufficient for each of 
the containers. One of these should be placed by the side of each 
jar, and then the sacks should be dropped carefully in quick suc ¬ 
cession into their corresponding jars in such an order that the 
operator shall not be exposed to the evolving vapors. When all 
is done the exit should be closed and locked, and a conspicuous 
label should be placed outside as a warning. 
