Nov. 26, 1917 
Hydrocyanic-Acid Gas as a Soil Fumigant 
429 
soil; into the open end of this tubing a rubber stopper (through which a 
short piece of glass tubing is inserted) is forced, effectually sealing the 
soil tube. The glass tubing in the stopper is the outlet through which 
the soil air is drawn. These tubes will be spoken of as “sampling tubes,” 
in order to distinguish them from the “soil tube” used later on in the ex¬ 
periment for studying the diffusion of gas in the soil. 
Experiments were begun in a clay-loam soil. In this the sampling 
tubes were sunk to a depth of 30 inches, and sodium cyanid in four differ- 
* ent forms was introduced into the soil at the same depth. 
1. Lump sodium cyanid was placed in the ground, and double the 
amount of sulphuric acid necessary to free the gas was poured on it, but 
the acid soaked into the ground before the sodium cyanid was dissolved. 
2. An aqueous solution of sodium cyanid without acid was poured 
down one of the tubes and air drawn off from a second tube 1 foot distant 
from the first and at the same depth, the air being aspirated through 25 
c. c. N/100 iodin; no trace of hydrocyanic-acid gas was shown in several 
trials. 
3. An aqueous solution of sodium cyanid was poured into a pipe as 
before, followed with the usual amount of acid necessary to release all the 
gas, likewise without recovering the gas by aspiration through an adjacent 
tube. 
4. Various forms of apparatus for generating gas on the surface and 
forcing it into the soil were used, the first one being known as the “ Babo 
generator,” in which only enough pressure was generated to force the 
gas out of the generator. A modified form of this apparatus was then 
prepared, in which large quantities of gas were generated, with slightly 
more pressure, but with no apparent advantage. Another style of 
generator was devised by Prof. Woodworth, giving a pressure of over 
100 pounds per square inch; but, on trial, results similar to those in the 
other experiments were obtained, there being no apparent advantage 
in generating gas in quantity or at a considerable pressure. These 
were the most promising forms of apparatus used in generating gas on 
the surface, but all were so unsatisfactory that attention was turned to 
generating gas in the soil. 
The actual generation of gas in the soil must be delayed during the 
operation long enough to allow for the covering of the generator with 
soil to a depth sufficient to prevent any loss of gas. Provision must 
also be made to prevent the filling of the generator with soil or the loss 
of acid before the reaction is complete. 
A pasteboard box, paraffined on the inside to resist the action of the 
acid, or a tin can with a tight-fitting lid, may be used for the generator. 
In order to delay the action of the acid on the sodium cyanid until the 
preparations are completed, we wrapped the cyanid in paper or placed 
it in pasteboard boxes and then dropped it into the acid solution. Table 
VI gives the result of an experiment in a dry clay-loam soil. 
