THE THERMODYNAMIC PROPERTIES OF MIXTURES OF WATER AND SODIUM-MONTMORILLONITE

JOSEPH LAWRENCE OLIPHANT, Purdue University

Abstract

Heats of immersion for mixtures of Na-montmorillonite and water at different initial water contents were measured calorimetrically and the results were used to calculate the relative partial specific enthalpy of the water at various water contents. From the relationships between free energy, enthalpy, entropy, and swelling pressure, along with swelling pressure data obtained previously in this laboratory, the partial specific entropy of the water was calculated. Then the swelling pressure was divided into enthalpic and entropic terms. These terms were compared separately to the same terms calculated theoretically by assuming that ions dissociated from the surfaces of the clay particles were the cause of swelling. It was found that dissociated cations could not account for the experimental results. Other mechanisms that might explain the experimental results were discussed. The isothermal compressibility of water mixed with Na-saturated montmorillonite was measured. It was found that the interparticle water was less compressible than pure bulk water. It was also shown that dissociated cations could not account for the entire decrease in compressibility of the water. The structure of the water close to clay surfaces was discussed in light of these compressibility data. Finally, the compressibility data were combined with previously determined data for the isobaric thermal expansibility and the isobaric heat capacity to yield the necessary data for the determination of the first derivative properties of the common thermodynamic variables of the system by means of the Bridgman relations.

Degree

Ph.D.

Subject Area

Agronomy|Cartography

COinS