Modern Aspects of Electrochemistry / Modern Aspects of Electrochemistry Bd.35 (PDF)

thermodynamic and transport properties, for example water vapor pressure, heat of vaporization, viscosity, electrical conductance..., as well as the influence of water concentration, temperature... on these properties, over the ranges of anticipated operating conditions, are essential in the design and operation of technical systems in which they are utilized.

With regard to scientific interest, the suggestion was made, now and then,1-8 that more progress in the understanding of very concentrated aqueous solutions could come from the consideration of solutions obtained by adding water to fused electrolytes rather than concentrating dilute aqueous solutions. Reciprocally, one would expect the structure of solutions where water plays the role of the solute, its mole fraction being less than about 0.5, be akin to that of the anhydrous molten electrolytes so that in the limit of vanishing water mole fraction the properties of the solutions would tend to those of the anhydrous electrolytes. From this point of view, any theoretical bringing-in regarding those solutions could contribute to more progress concerning the anhydrous electrolytes themselves.

Recently, electrolyte-water systems were investigated in the liquid phase over practically the whole water concentration range. Since these systems bridge the gap between anhydrous electrolytes and dilute aqueous solutions, they are designated by the expression "bridging electrolytewater systems", the electrolyte being a single one or a mixture of several components. Bridging systems lie at the heart of the present chapter. Electrolyte-water systems which do not cover the entire concentration range will also be examined or taken into account inasmuch as they cover a sufficiently large water mole fraction region, starting especially near the anhydrous electrolyte, so that they can give information on the transition of properties between those at the two extremes of the concentration scale.