Nov. 26, 1917 
Hydrocyanic-Acid Gas as a Soil Fumigant 
433 
These requirements show the wide range of absorptive power of 
different soils, varying approximately from 3,030 pounds of sodium 
cyanid for a clay loam to 483 pounds for a gravelly soil. The figures 
given of the cost for the lighter soils indicate that the use of sodium 
cyanid, while comparable with fumigation with carbon disulphid, is not 
within the range of economy except in small areas, even when the value 
of the gas as a nitrogenous fertilizer is considered. The fumigation of 
heavy soils is very much more expensive. 
From the difficulties encountered while working with the generators 
it seemed necessary to study more carefully the rate of diffusion and 
absorption of hydrocyanic-acid gas through the various soil media 
and the effect of soil moisture on this movement. Five experiments 
were made covering different types of soil and varying amounts of soil 
moisture. After introducing the hydrocyanic-acid gas into the soil, 
tube readings were taken at intervals ranging from a few minutes to 120 
hours. 
1. Heavy clay soil—Readings taken following the introduction of 
the hydrocyanic-acid gas and 48 hours later. 
2. Wet clay-loam soil containing considerable humus—Readings 
taken immediately after charging the tube. 
3. Very sandy, beach soil, containing about 5 per cent of broken shell 
slightly moist—First reading taken immediately, the next 16 hours later. 
4. Clean river sand washed and dried at a temperature of 200° 
C. to remove the soil, organic matter, and moisture—Readings taken 
immediately after charging with gas and 5 days later. 
5. Sand washed and dried as above and afterwards saturated with 
water—Readings taken immediately. 
For this purpose a copper soil testing tube 36 inches long and 2 inches 
in diameter was made. One end of the testing tube is closed with the 
exception of a ^-inch tube, the opposite end is closed with a rubber 
stopper through which is inserted a >^-inch glass tube; at intervals of 6 
inches along the sides ^-inch tubes are inserted; to all of these small 
tubes a short piece of rubber hose is attached which may be closed with 
clamps. Air from a standard solution of hydrocyanic-acid gas was 
drawn in through the tube inserted in the stopper, by applying a vacuum 
at any of the tubes along the sides or at the opposite end of the testing 
tube, all the openings being closed except the ones where the air was 
admitted. Then by detaching the tube from the acid solution and draw¬ 
ing in pure air at the same point the amount of gas in that section of the 
tube could be measured, and also the amount lost could be calculated. 
On account of the small amounts of gas present in the different sections, 
qualitative tests only with silver nitrate (AgNo 3 ) was substituted for 
the iodin method. This overcomes the error from volatilization of 
