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Gas and vapour movements in the soil: I. The diffusion of vapours through porous solids

  • H. L. Penman (a1)

The dependence of the coefficient of diffusion, D, upon the porosity, S, of a granular solid is investigated experimentally. For steady state conditions, using carbon disulphide and acetone vapours, it is shown that a curve connecting D/D0 and S can be drawn which is independent of the nature of the solid, its moisture content and, within limits, its texture. For a limited range of values of S (0·0 < S < 0·7) a good approximation is D/D0 = 0·66S and over this range the diffusion coefficients are larger than those found by Buckingham for carbon dioxide.

Investigation of the non-steady state shows that in soils the attainment of pressure equilibrium is retarded by adsorption, and it is suggested that Buckingham's low values for steady-state conditions can be attributed to premature observations of the diffusion rates; the steady state had probably not been attained when his measurements were made.

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Cabman, P. C. (1939). J. agric. Sci. 29, 262.
Chapman, S. (1928). PUl. Mag. 5, 630.
Higgins, J. C. & Pollard, A. G. (1937). Ann. appl. Biol. 24, 895.
I.C.T. (International Critical Tables) (1929). 5, 62. New York.
Keen, B. A. (1931). The Physical Properties of the Soil, chap. 10. London.
Melloe, J. W. (1925 a). Comparative Treatise on Inorganic and Physical Chemistry, 6, 99. London.
Melloe, J. W. (1925 b). Comparative Treatise on Inorganic and Physical Chemistry, 6, 109. London.
Romell, L.-G. (1922). Medd. Stat. Skogsforsoks. 19, 125.
Smith, F. B. & Brown, P. E. (1933). Soil. Sci. 35, 413.
Trautz, M. & Müller, W. (1935). Ann. Phys., Lpz., 22, 313.
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The Journal of Agricultural Science
  • ISSN: 0021-8596
  • EISSN: 1469-5146
  • URL: /core/journals/journal-of-agricultural-science
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