THE ADSORPTION OF ALIPHATIC ACIDS FROM AQUEOUS SOLUTIONS BY POROUS CARBONS

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Abstract
The maximum adsorptions of the lower members of the mono- and di-carboxylic acids from aqueous solutions were determined for coconut charcoals of different degrees of activation. Based on these results, a method for estimating pore size was applied to the more finely porous charcoals. To corroborate the pore sizes estimated from acid adsorption, pore size – area distributions were calculated from measurements of the water vapor sorption isotherms of the charcoals. An alternation in the maximum amounts of adsorbed acids was observed with the more active charcoals. Acids with an even number of carbon atoms had larger adsorptions than acids with an odd number. The alternation was much more marked for the di- than for the mono-carboxylic acids. A remarkable correlation between the alternation of adsorptions and of melting points of both acid series was observed. An explanation for the general phenomenon of alternation based on rotational motion of molecules in the solid state is given as an alternative to the widely held one based on tilting of molecular chains.