Nov. 26 ,1917 
Hydrocyanic-Acid Gas as a Soil Fumigant 
425 
effect (not shown in Table III) was the more rapid growth of the seed¬ 
lings and their deeper color in the dilution immediately adjacent to 
where the definite retarding action ceased. A diagram of the heights is 
shown in figure 1. 
The maximum height of the alfalfa seedlings was reached at a dilution 
of 0.0022 gm. of sodium cyanid per liter (equivalent to 0.0006 per cent 
of hydrocyanic acid over the solution). 
EFFECT OF HYDROCYANIC-ACID GAS ON CUTTINGS AND SEEDLINGS 
I. PLANTS IN SOIL WATERED WITH HYDROCYANIC-ACID GAS SOLUTIONS 
Seedlings of lettuce and turnip and six weeks' old turnips and beets 
were planted in tumblers containing soil, and watered with hydrocyanic- 
acid gas solutions, 1 ounce of the solution being used to the tumbler. 
1 3 
r 
Fig. i.—D iagram showing the relative heights of the alfalfa seedlings grown in hydrocyanic-add gas solu¬ 
tions produced by adding sulphuric add to sodium cyanid in solution. 
The first solution contained 18.779 gm. of sodium cyanid per liter, with 
a proportionate amount of acid as in the germinating experiments, giv¬ 
ing approximately a 5.6 per cent of hydrocyanic-acid gas over the solu¬ 
tion, the amount of sodium cyanid being reduced one-half each time 
through a series of 12 graduations, the thirteenth culture being a con¬ 
trol of pure water. One or more plants were placed in each tumbler 
and sealed with paraffined paper held in place with a rubber band. The 
covering paper was slit to the center, the plant inserted in the opening 
and the edges of the paper drawn together and sealed with melted 
paraffin close up to the stem of the plant. In this way the roots were 
exposed to the hydrocyanic-acid solution and to a sodium-sulphate solu¬ 
tion, but the gas did not come in contact with the leaves. 
All the plants in the first five containers were killed and only in the 
soil watered with the ninth solution which contained 0.0733 gm. of 
sodium cyanid per liter (equivalent to 0.0219 per cent of hydrocyanic 
acid over the solution) did the plants remain normal. 
