Gas and vapour movements in the soil: II. The diffusion of carbon dioxide through porous solids

Apparatus for measuring the rate of diffusion of carbon dioxide through granular solids is described and the results obtained with it are shown to conform to the curve connecting D/D0 and S previously obtained for carbon disulphide and acetone. The equation D/D0 = 0·66S, which it is suggested should replace Buckingham's equation D/D0=S2, is applied to a discussion of soil aeration, and it is shown that at all porosities the rate of diffusion of carbon dioxide from the soil is sufficient to account for normal respiration without invoking the assistance of meteorological changes. A further application of the equation to water vapour movement in soils is briefly discussed.