SOIL GASES. 



By J. WALTER LEATHER, \ .D., F.I.O. 



{Imperial Agricultural Chemist, Agricultural Research Institute, 

 Pusa, Bengal). 



At page 5 of their recent comnumication on tlie composition of soil 

 gases^ Messrs Russell and Appleyard give some data regarding gas which 

 was extracted from portions of soil which had been placed in flasks, 

 the air pnmpcd out and the soil then allowed to stand for one or more 

 days. The authors state that "the total amount of gas given up is 

 not great." As a matter of fact a little consideration shows that the 

 volume of this gas was indeed comparatively very large. 



This gas may be compared with that originally included in the soil 

 mass. Judging from the data given on page 44, the "free air"' varied 

 from 8 to 18 c.c. per Gl-8 c.c. or (61-8 x 2-31) = 11.'5 grams soil, or from 

 5-6 c.c. to 12-G c.c. per 100 grams dry soil. Reference to Table 111 

 shows that the gas which was obtained from the several ])ortions of 

 soil, subsequent to the removal of the air of the Masks, was considerably 

 greater than the "free air" of the soil. 



Considering secondly the composition of this gas, it is evident that 

 its origin is certainly not accidental. The authors state that it consists 

 "mainly of carbon dioxide with some nitrogen." Here again the 

 figures hardly support such a definition, for the nitrogen exceeds the 

 carbon dioxide in a number of the samples. Again, although to a 

 certain extent the carbon dioxide could be assumed as having been 

 derived from calcium bicarbonate solution in the soil, its cjuautity is 

 very far greater than could be present in this form. The water present 

 could only hold a certain amount of calcium bicarbonate in solution, 

 and it is from this item that the above deduction can be made. Lastly 

 the volume of nitrogen obtained is very far in excess of what could be 

 assumed to be condensed or dissolved on soil jjarticles. 



> This .Journal, Vol. vii. pp. 1-48. 



