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The solution and diffusional extraction of solid materials from porous membranes is investigated theoretically and experimentally.

A method has been suggested for determining mass transfer coefficients at the liquid-liquid interface through the substance absorption in the attenuated total reflection (ATR) spectrum. The aim was achieved with a cuvette where one of the liquid phases was reduced to a 10–15 μm thick layer incorporated in a teflon membrane stuck to the optical prism and so immobilizing the liquid. The thickness indicated allows to consider the diffusion processes in both phases as one-dimensional. The mathematical model applied differs from that of A. Vignes [19] by the fact that the coupled diffusion system refers to domains with final sizes. The experimental data processing was done by computer on the basis of orthogonal expansion terms. The mathematical treatment includes the observation of the mass transfer coefficient at the interface simultaneously with that of the partition coefficient between both liquid phases. Compared with the existing direct physical methods the one suggested by us resorts to simple experimental tools and leads to quantitative results.