Abstract

The object of the work presented in this thesis was to obtain quantitative values of the thermodynamic changes in water upon adsorption by silica. Two methods were used. The first was a determination of the differential entropy and heat of adsorption independent of any theory of adsorption. The second method included a new interpretation of the "c" constant of the Brunauer, Emmett, and Teller Theory in which c was expressed in terms of the standard free energy of adsorption. The experimental data gave satisfactory results in determining the differential heat and entropy of adsorption. The results obtained in determining the standard entropy and heat of adsoption of use of the B.E.T. equation were questionable. The standard entropy of adsorption as determined by the B.E.T. equation was less negative than the corresponding entropy of condensation. It is unlikely that water molecules adsorbed on silica would have more freedom than water molecules in the liquid state. The adsorption of water on silica appears to be a van der Waals type of adsorption, the heats of adsoption being only 1-4 k. cal. greater than the heat of condensation of water.

Degree

College and Department

Physical and Mathematical Sciences; Chemistry and Biochemistry

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