8 
CHEMICALS AND OTHER SUPPLIES. 
In the fumigation of mills, warehouses, elevators, and other struc- 
tures and inclosures infested by insects, especially the Mediterranean 
flour moth and some other soft-bodied insects, in stored cereals, with 
hydrocyanic-acid gas two chemicals are used, both poisonous and 
dangerous to handle. They are cyanid of potassium, called also 
potassium cyanid and cyanid of potash, of a high grade or chemically 
pure (98-99 per cent), concentrated sulphuric acid having a specific 
gravity of about 1.83 or 1.84 (equivalent to 66° Baumé), and water. 
The standard commercial sulphuric acid will answer. 
Cyanid of potash (KCN or KCy), the first ingredient, is a white 
crystalline salt, permanent in dry air, but rapidly decomposable or 
deliquescent in a moist atmosphere, when it gives off an odor of 
hydrocyanic or prussic acid. It is readily soluble in water, has a 
bitter taste, and is extremely poisonous. 
Sulphuric acid (H,SO,), the chemical used in liberating the gas, is 
so well known as scarcely to require description at this point. It 
might be well, however, to state that it is known commercially also 
as oil of vitriol or simply ‘vitriol,’ and is a dense, oily-looking fluid, 
colorless when pure, having when concentrated a specific gravity of 
about 1.8, and containing about 90 per cent H,SO,. It is nearly 
twice as heavy as water, and in action it is powerful, being corrosive 
to both animal and vegetable substances. 
Hydrocyanic acid (HCN or HCy), the resultant gas liberated by 
combining cyanid of potash and sulphuric acid, is one of the most 
energetic poisons known to science. A single drop of the pure acid 
placed inside of the eye causes instant death. When taken internally 
it causes paralysis of the heart, of the respiratory center, and of the 
vasomotor region of the medulla. The immediate cause of death in 
most cases is due to obstruction of the respiration or to stoppage of 
the heart’s action. 
The purity of the cyanid of potash and sulphuric acid to the 
degree indicated above is essential to the success of fumigation, 
and efforts should be made to obtain these chemicals through thor- 
oughly reliable firms, and if there is any doubt as to their strength 
they should be submitted to analysis. Many of the disappointments 
and failures in fumigation have come from the employment of impure 
cyanid of potash or acid below the standard strength. These two 
agents are, however, now in such common use for fumigation pur- 
poses that with ordinary care in their purchase there is little risk in 
this direction. 
[Cir. 112] 
