Abstract
The modified pore model for diffusion, which was proposed in our previous paper by taking into account the reduction of pore radius by the bulkiness of diffusants, has been applied to the diffusion of small simple compounds having -SO-3, -COO- or -OH group through water-swollen cellophane. Diffusion coefficient, D'p (0), of each compound in the water-filled pore in cellophane has been obtained from the data of steady state permeation, on this model. By comparison of D'p (0) with the diffusion coefficient, Db, in the bulk water, obtained by capillary method, the following information has been obtained:
1) D'p (0) of small inorganic compounds, such as HCl and KCl, depends on the larger size of the component ions, while that of the other organic, relatively long compounds, depends on the slightly larger length than the radius of minimum cross-section of the diffusant molecule as was found for the diffusion of several dyes.
2) For the compounds having -COO- group, D'p (0) is generally smaller than Db, while for the compounds having -SO-3, D'p (0) is considerably larger than Db. These facts were explained by invoking to the difference in the effects of -COO- and -SO-3 on the water structure: the former acts as structure maker and the latter as structure breaker.
3) For alkyl sulfonic acids, an additional flux due to the considerably large amount of the diffusant adsorbed weakly on the pore wall has been observed.
4) Alcohols and phenols are considered to behave as molecular aggregates of two or three molecules in water. D'p (0) of these compounds seems to depend on the radius of these aggregates.
