Concentrated Aqueous Electrolyte Solutions: and Approach From the Glassy State and the High Concentration Limit. I. Temperature Studies of Electrical Conductance, Fluidity and Density. Ii. Low Temperature Dielectric Relaxation Studies
Abstract
Transport processes, electrical conductance and fluid flow, are investigated in a series of concentrated aqueous electrolyte solutions as a function of concentration and temperature. Advantage is taken of the ability of these solutions to readily supercool and form glasses to extend the temperature range examined beyond that normally studied. The results are interpreted in terms of current theory of glass forming liquids. "Ideal" glass transition temperatures are calculated by fitting the transport property, W(T) to the modified V.T.F. equation where A, D, and To are constants and T is the absolute temperature.Two distinct regions of solution transport behavior are suggested in addition to the well known Debye-Hückel dilute region. (i) a relatively simple high concentration region where there is effectively no "bulk" solvent water present and the cohesion as indicated by the glass temperatures is a simple linear function of mole percent concentration and (ii) a complex intermediate region where there is present both "bulk" and oriented (in the ion co-sphere) water and is subject to composition fluctions and ultimate phase separation into salt-rich and water-rich phases at lower temperatures.Dielectric and conductivity relaxation studies are carried out in several concentrated solutions in the frequency range 200 Hz - 2MHz in the temperature region at and just above the solution glass temperatures. The results are analyzed using the Macedo, Bose, Litovitz dielectric modulus notation.Results of both of these studies indicate the presence of an added protonic conductivity in these solutions arising out of the basicity of the electrolyte anions. This effect is most pronounced at low temperatures near the glass transition where the normal ionic mobility approacheszero.
Degree
Ph.D.
Subject Area
Physical chemistry|Chemistry
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