Yizhak Marcus

EFFECT OF IONS ON THE STRUCTURE OF WATER: STRUCTURE MAKING AND BREAKING

4. Structure of Ionic Hydration Shells 1351 4.1. Results from Diffraction Experiments 1351 4.1.1. X-ray Diffraction 1351 4.1.2. Neutron Diffraction 1351 4.2. Results from Computer Simulations 1352 4.3. Results from Spectroscopic Measurements 1354 4.3.1. Vibrational Spectroscopic Measurements 1354 4.3.2. EXAFS Spectroscopy 1354 4.3.3. NMR Relaxation Studies 1355 4.3.4. Dielectric Relaxation Studies 1355 4.4. Summary of the Structure of Ionic Hydration Shells 1355

Solubility and solvation in mixed solvent systems

Au cours de ce congres, des aspects theoriques et experimentaux sur la solubilite ont ete abordes

Thermodynamics of ion hydration and its interpretation in terms of a common model

The relationship between the conventional standard molar thermodynamic quantities of hydration of an ion and the correspon— ding quantities of solvation, that are due entirely to its inter— actions with its aqueous environment, is presented. The TATB assumption, i.e., that quantities pertaining to the tetraphenyl— arsonium cation equal those pertaining to the tetraphenylborate anion, is applied to the standard enthalpy, entropy, and Gibbs energy of hydration of ions, and to the standard partial molar heat capacity and volume of aqueous ions. A model of the hydrated ion, consisting of a layer of completely immobilized water molecules surrounded by a dielectric continuum affected by the field of the ion and water the structure of which is modified, is presented. The thickness of the first layer and the number of water molecules in it is proportional to the radius of the ion. The model is shown to be compatible with all these thermodynamic quantities.

Effect of ions on the structure of water

Water is a highly structured liquid, as indicated by its stiffness (cohesive energy density) and being ordered (large entropy of vaporization), its three-dimensional hydrogen-bonded network being its most outstanding feature. The extent of this network depends on the definition of the hydrogen bond, and both computer simulation and thermodynamic data yield a consistent picture. The effects of ions on this network in dilute aqueous solutions have been studied from dynamic, thermodynamic, spectroscopic, and computer simulation aspects. A classification of ions from those that are highly water-structure-breaking ions through borderline cases to those that are highly water-structure-making ions results from such studies.

Transfer of ions between solvents: Some new results concerning volumes, heat capacities and other quantities

Abstract Standard molar Gibbs free energies, enthalpies, and entropies of transfer between solvents have been reported by many authors for a large number of cations (mainly uniand divalent) and anions (univalent). These quantities could be related to properties of the ions and the solvents, permiting predictions of such quantities. Also the transfer Gibbs free energies of divalent anions (sulfate and others) predicted on this basis agree with reported values. Only recently have the author and coworkers been able to extend this approach to the partial molar volumes and heat capacities of ions in various non-aqueous sol-!ents using a multivariate statistical treatment, based, however, on a much more modest database. For these structure-related quatities the electrical properties of the solvents (permittivities, dipole moments) are not relevant, whereas their hydrogen bonding abilities are.

On the solubility of non-ionic organic solutes in seawater

Abstract Given the solubilities of non-ionic organic solutes in water, their solubilities in seawater are obtained by correlation expressions involving two descriptors for the constituent ions (or salts) of seawater and two descriptors of the solutes. The former are the standard partial molar volumes and the intrinsic molar volumes and the latter are the molar volume (the Le Bas variant of it) and either the Hildebrand solubility parameter δH or the Kamlet–Taft solvatochromic π*.