THE ABSORPTIVE PROPERTIES OF SOILS 367 



271. Absorption of nitrogen and oxygen. — Nitrogen 

 is absorbed by soils to a greater degree than is oxygen. 

 The latter probably is of greater importance to soil fer- 

 tility, as its absorption is accompanied by oxidation of 

 other absorbed gases. Because of their absorptive prop- 

 erties and their great surface area, soils have strong 

 oxidizing power. 



The absorption of gases by soils is largely an absorp- 

 tion phenomenon, the gases being condensed on the 

 surface of the particles. Von Dobeneck^ has shown 

 that the absorption is greater, the finer the particles 

 of soil; but this increase is not directly proportional 

 to the increase in surface, large particles apparently 

 having a greater adsorptive power than their surface 

 area would indicate. 



272. Relation of temperature to gas absorption. — 

 The temperature of the soil influences its absorptive 

 properties for vapors. As the temperature increases the 

 absorption becomes less. Hilgard ^ does not find this 

 to be the case (par. 136). He exposed soils to a moisture- 

 saturated atmosphere and found that they absorbed 

 more moisture at high than at low temperatures. In 

 his conclusions, however, he is doubtless in error. All 

 the work previous to his gave a directly contrary result, 

 and a more recent investigation by Patten and Gallagher ^ 

 confirmed the work of the earlier investigators. 



^Von Dobeneck, A. F. UntersueliungeD. liber das Adsorp- 

 tionsvermogen und die Hygroskopizitat der Bodenkonstit- 

 uenten. Forseb. a. d. Agri.-Pbysik., Band 15. Seite 163-228. 

 1892. 



2 Hilgard, E. W. Soils, pp. 196-198. New York, 1906. 



3 Patten, H. E., and Gallagher, P. E. Absorption of Gases 

 and Vapors by Soils. U. S. D, A., Bur. Soils, BuL 51, pp. 31- 

 35. 1908. 



