Membranes of solid and glassy materials

A membrane can be either a liquid or a solid. Its electrical properties arise when it allows transport of an ion of one charge but not that of another. Membranes are usually sufficiently thick that one can distinguish an inside region and two outer boundary regions which are in contact with electrolyte solutions. Two types of membranes are considered here (1) membranes of solid and glassy materials (2) liquid membranes with dissolved ion-exchanging ions or neutral ion carriers (ionophores). In fact all of these membranes are involved in ion exchange. It is important to understand how this process affects the potentials which develop in the system at both sides of the membrane. 

The use of ISEs in non-aqueous media(for a survey see [125,128]) is limited to electrodes with solid or glassy membranes. Even here there are further limitations connected with membrane material dissolution as a result of complexation by the solvent and damage to the membrane matrix or to the cement between the membrane and the electrode body. Silver halide electrodes have been used in methanol, ethanol, n-propanol, /so-propanol and other aliphatic alcohols, dimethylformamide, acetic acid and mixtures with water [40, 81, 121, 128]. The slope of the ISE potential dependence on the logarithm of the activity decreases with decreasing dielectric constant of the medium. With the fluoride ISE, the theoretical slope was found in ethanol-water mixtures [95] and in dimethylsulphoxide [23], and with PbS ISE in alcohols, their mixtures with water, dioxan and dimethylsulphoxide [134]. The standard Gibbs energies for the transfer of ions from water into these media were also determined [27, 30] using ISEs in non-aqueous media. 

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