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Activation Energy for Ion Movement in Thin Water Films on Montmorillonite
Author(s) -
Oster James D.,
Low Philip F.
Publication year - 1963
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1963.03615995002700040006x
Subject(s) - relative humidity , montmorillonite , adsorption , desorption , chemistry , activation energy , conductance , ion , water content , humidity , analytical chemistry (journal) , thermodynamics , environmental chemistry , geology , physics , organic chemistry , mathematics , geotechnical engineering , combinatorics
Desorption isotherms were determined for Li‐, Na‐ and K‐ montmorillonite at several temperatures. Relative partial molar entropies of the adsorbed water were calculated from these isotherms. The specific conductance of each clay was determined as a function of temperature at water contents corresponding to one layer, two layers and several layers of adsorbed water. Also, the d 001 spacings were determined at the two lower water contents by X‐ray analysis. For the determination of specific conductance, the clays were packed into porous glass conductance cells which allowed them to equilibrate with an atmosphere of controlled relative humidity. The relative humidity was changed with the temperature in order to maintain the desired water content. Then the specific conductance of each clay was plotted against the reciprocal of the absolute temperature to obtain the activation energy for the movement of the adsorbed ion. The resulting activation energies were interpreted in terms of ion‐oxygen interaction at the mineral surfaces and in terms of the orderliness of the adsorbed water as indicated by the entropy data.