HYDROCYANTIC-ACID GAS AGAINST HOUSEHOLD INSECTS. 3 
In the use of sodium cyanid the grade known) as “98 to 99 per 
cent’! should be procured, and combined with the other materials 
according to the following formula :? 
NOCTUM Cy anige melee as Seale 2: i Te eee avoirdupois ounce__ all 
SCHLTR EN CIEL re) Cl et ere ee eS ee ae fluid ounces__ 13 
AVE Sy OE ca ee TN 7 Ed Se ee ee ee dO ao 
In this combination sufficient sulphuric acid is added to liberate 
completely the excess hydrocyanic acid in the sodium cyanid, since 
in the use of this chemical a greater amount of sulphuric acid is 
necessary for the complete exhaustion of the cyanid. 
For loosely constructed frame houses the foregoing amounts may 
be doubled for each 100 cubic feet. The cyanid costs from 25 to 50 
cents a pound, and the sulphuric acid (thick or more sirupy com- 
mercial brand) about 4 cents a pound. 
The purity of the cyanid and sulphuric acid to the degree indicated 
is essential to the success of the fumigation. 
Druggists and cther retail dealers generally have in stock only 
impure grades of sodium cyanid, used for other technical purposes 
but unsuitable for fumigation on account of the greater or less per- 
centage of sodium chlorid (common salt) and other adulterants 
contained. The presence of salt, as noted in relation to potassium 
eyanid (see footnote”, p. 2), greatly reduces the amount of hydro- 
eyanic-acid gas given off, and it is therefore highly important to 
insist on the best commercial grade of sodium cyanid, known as 
98-99 per cent, containing 51 per cent cyanogen, such as is manu- 
factured especially for fumigation purposes. The greater amount of 
eyanogen (available hydrocyanic-acid gas) in cyanid of sodium 
necessitates the use of a correspondingly greater amount of acid, as 
indicated in the formula for sodium eyanid. 
DIRECTIONS FOR FUMIGATION. 
Before beginning the fumigation the house must be vacated. It is 
not necessary to remove any of the furniture or household belongings 
unless of polished nickel or brass, which may tarnish a little. Liquid 
or moist foods, as milk, meats, or other larder supplies that are not 
dry and might absorb the gas, should be removed from the house. 
All fires should be put out; for while the gas will not burn at the 
dilution employed in fumigation, it is as well to take no risks. 
The cubic contents of each room on each floor should be carefully 
computed and a tabular statement prepared, such as the one given 
1This grade was formerly known as 128-130 per cent cyanid, since an equal amount 
by weight of chemically pure sodium cyanid liberates 35 per cent more hydrocyanic-acid 
gas than does pure potassium cyanid, and this was expressed by designating the pure sodium 
eyanid as 133 per cent. 
2 For rapid work it may be stated that in either of the foregoing formulas, where the 
eyanid is weighed out in pounds avoirdupois, the same proportions may be used as 
expressed in the formulas, the acid and water being measured in pints. 
