97—DIFFUSION OF SOME SULPHONIC ACIDS IN KERATIN IN THE PRESENCE OF WATER AND ALCOHOLS

Abstract

The transfer rates of a series of alkylbenzene-sulphonate ions between aqueous solutions and horn keratin have been measured by radio-tracer techniques. The rates are increased by the addition of n-propanol and n-butanol to the external solutions, the effect being greater for the larger alkyl groups and for higher concentrations of ion in the keratin. Evidence is presented that transfer rates (whether an alcohol is present or not) are governed by Fickian diffusion within the keratin. Butanol is prefereritially absorbed, and it appears that the resulting acceleration of organic ions is not due to swelling action. It is suggested that the explanation is to be found in terms of the hydrophobic interactions on which the affinity of an ion depends. When the solvent is water alone, these interactions immobilize the ion on the keratin structure, and the fraction of ions remaining free is inversely related to the affinity. With a mixed solvent, interactions are possible between the free ions and the alcohol; this increases the fractions of ions free.