Abstract
Tannic acid is taken up by gelatin and casein from aqueous solution according to the adsorption isotherm. The temperature coefficient of this sorption is negative. From aqueous alcohol and aqueous acetone solution, the sorption obeys Henry's law. The sorption of tannic acid by hide powder was measured together with the swelling of the latter and the two found to vary in a parallel manner. The same relation was found for the sorption of tannic acid by hide powder with varying alkalinity. The sorption of sodium hydroxide on hide powder obeys the adsorption isotherm. When various acids are used to adjust the system to constant pH, the sorption of tannic acid on hide powder varies essentially as the degree of swelling of the adsorbent. Relations are shown between the viscosities of ethyl alcohol-water mixtures and the sorption of tannic acid on hide powder from corresponding solutions. No lyotropic effect is obtained upon the addition of electrolytes to the sorption system tannin-gelatin. The results obtained are discussed from the point of view of the mechanism of vegetable tanning, and it is concluded that the amount of sorption depends to a great extent upon the degree of swelling of the adsorbent.
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