40 
THE COLORADO EXPERIMENT STATION 
hold down the fumes. Allow the blanket to remain for a half hour 
at least, and the ants will be dead. If the hill is a very large one 
it would be well to make two or three holes for the carbon bisul¬ 
fide. 
To kill prairie dogs, pour three or four ounces of the liquid 
on a ball of cotton and roll the latter down the prairie dog hole and 
quickly fill the mouth of the hole with dirt. Dry horse droppings 
or pieces of gunny sacking may be used in place of the cotton. 
For the destruction of the woolly-louse of the apple, thrust a 
crow-bar or other sharp instrument into the ground to the depth of 
one foot or a little more, and at a distance of two feet from the 
crown of the tree and upon three sides of the tree. In each of 
these holes pour one ounce of the carbon bisulfide and close the 
holes quickly with damp earth. This is a cheap and effectual 
remedy and, if care is taken to have the holes made two feet from 
the tree and to have only about an ounce of the liquid put in a 
hole, there will be little or no danger of killing the trees. 
This substance is expensive when purchased in small quanti¬ 
ties at a drug store. It may be obtained quite cheaply if pur¬ 
chased in 50-pound lots, from Mr. Edward R. Taylor, Cleveland, 
Ohio. Write for prices. 
27. HYDROCYANIC ACID GAS. 
This gas has come into very general use, particularly in the 
orange growing sections of the country, for the destruction of scale 
insects. It may also be used for the destruction of insects in mills 
and in dwellings and in closed receptacles generally. Some of the 
best nursery men have adopted the excellent plan of fumigating all 
their nursery stock with hydrocyanic acid gas before shipping to 
their customers. This should always be done. 
The chemicals of which this gas is made are cheap and are 
used in the following proportions: 
Potassium cyanide (of 98 per cent, purity) — 1 ounce. 
Commercial sulfuric acid.1 ounce. 
Water.3 ounces. 
The above quantities are sufficient for a space of 100 cubic feet 
for the fumigation of dormant trees and plants (nursey stock). It 
may be used in the same strength, or even stronger, for the fumi¬ 
gation of mills, houses, clothing and the like. 
The tent, building or receptacle in which the fumigation is to 
take place, should be as tight as possible. The less wind there is 
the better, if the fumigating room is not very tight. 
The gas should be generated in an earthen jar, or wooden 
bucket or tub. The chemicals must be added hi the following 
order: First put in the water; then add the acid; and, after the 
