The Entropy of Deep Eutectic Solvent Formation.

The standard entropies of deep eutectic solvents (DESs), which are liquid binary mixtures of a hydrogen bond acceptor component and a hydrogen bod donor one, are calculated from their molecular volumes, derived from their densities or crystal structures. These values are compared with those of the components-pro-rated according to the DES composition-to obtain the standard entropies of DES formation Δ. These quantities are positive, due to the increased number and kinds of hydrogen bonds present in the DESs relative to those in the components.

A relationship between the effect of uni-univalent electrolytes on the structure of water and on its volatility.

The effect of ions on the structure of water in dilute solutions, whether they are structure-makers or structure-breakers, is manifested also in the volatility of the water. For more than 40 uni-univalent electrolytes, there is a linearly increasing relationship between 2φ(m = 0.4) - φ(m = 0.

Solubility Parameter of Carbon Dioxide-An Enigma.

The solubility of gaseous carbon dioxide in a variety of solvents has been extensively studied, the solute interacting with most solvents via dispersion forces. Hence, its Hildebrand solubility parameter, δ, may be used to predict its dissolution in liquids. The usual definition of δ involves Δ , the molar enthalpy of vaporization, strictly applicable to liquids.

Effects of Solvent Properties on the Anion Binding of Neutral Water-Soluble Bis(cyclopeptides) in Water and Aqueous Solvent Mixtures.

In this study, the anion-binding bis(cyclopeptide) is introduced, which dissolves freely in water, affording up to 10 mM concentrations, thanks to triethylene glycol-derived substituents in the cyclopeptide subunits and the linker connecting them. Binding studies provided evidence that the anion affinity previously demonstrated for less-soluble analogs of this compound is retained under highly competitive aqueous conditions. The highest affinity in water was observed for iodide, closely followed by sulfate anions, whereas binding of soft and weakly coordinating anions could not be observed.

Structure of Mixtures of Water and Methanol Derived from Their Cohesive Energy Densities and Internal Pressures from Subambient Temperatures to 473 K.

The cohesive energy densities, ced, and the internal pressures, P, of aqueous methanol mixtures are calculated from literature data for the entire composition range over a temperature range of 273-473 K, at saturation pressures up to 373 K and at 7.0 MPa above this temperature. Ratios P/ced are measures of the "structuredness" of the studied fluids, and the small values noted signify "tight" structures, due to hydrogen bonding.

Electrostriction of Several Nonaqueous Solvents under Ambient Conditions and Solvation Numbers of Ions in Them.

The diminution of the mean molar volume on electrostriction, ΔelVS, in the large electrical field of ions solvated by several solvents that are useful for the dissolution of electrolytes is presented. The solvents dealt with are ethanol, trifluoroethanol, 1,2- and 1,3-propanediols, glycerol, 2-butanone, 1,1- and 1,2-dichloroethane, pyridine, benzonitrile, nitromethane, nitrobenzene, formamide, and dimethylformamide. The inverse dependence of the relative molar electrostriction volume on the dipole moment of the solvents is suggestive of the fact that the larger the polarity of the solvents, the more they are able to withstand the compressive effect of the electrical field.

Concentration dependence of ionic hydration numbers.

Isothermal compressibility data of 23 aqueous electrolyte solutions at 25 °C from the literature are used to calculate their hydration numbers, which diminish as the concentration increases. Their limit at very high concentration is near the "number of adsorption sites" of water molecules on the ions, obtained by the BET method. On the contrary, hydration numbers obtained from ultrasound speed measurements yielding isentropic compressibilities cannot be valid, being much too large at infinite dilution.

The molar volumes of ions in solution, part 7. Electrostriction and hydration numbers of aqueous polyatomic anions at 25 °C.

The standard partial molar volumes of 16 polyatomic more-or-less globular anions in aqueous solutions at 25 °C were calculated as the sum of the intrinsic and (negative) electrostrictive volumes and compared with the experimental values. The intrinsic volumes used an empirical additive to the bare ionic radius to account for void spaces near the ions. The volume shrinkage due electrostriction was calculated according to the shell-by-shell electrostatic method.

The compressibility and surface tension product of molten salts.

Products of the isothermal compressibility, κT, and the surface tension, σ, that have been discussed in the literature for liquids in general are shown for over 60 molten salts. The applications of the scaled particle theory of Mayer and the simplified corresponding states correlation of Harada et al. [Ind.

Individual ionic surface tension increments in aqueous solutions.

Surface tension increments by aqueous electrolytes, kE = [γ(cE) - γ(W)]/cE, can be split into the ionic values, ki (kE = Σνiki), on an arbitrary but plausible manner, notwithstanding the effects of counterions on the behavior of specific ions. Values for 41 ions, mono- and polyatomic and uni- and multivalent, are presented in conjunction with some other ionic properties. The surface potential increments of electrolytes, ΔΔχ = ΔχE (at cE = 1 M) - ΔχW, depend linearly on the kE values for four anion series with common cations and on the differences between cation and anion ki values.

Volumes of aqueous hydrogen and hydroxide ions at 0 to 200 °C.

The electrostriction of aqueous hydrogen and hydroxide ions at infinite dilution was calculated by the shell-by-shell method over the temperature range 0 to 200 °C. The calculation required an estimate of the ionic radius of these ions, and comparison with data for aqueous lithium, sodium, and fluoride ions provided values for the nominal sizes of the hydrogen and hydroxide ions in solution. From the volumetric standpoint, these sizes are surprisingly smaller than the size of a water molecule.

The standard partial molar volumes of ions in solution. Part 5. Ionic volumes in water at 125-200 °C.

The standard partial molar volumes, V(∞)(i,T), of 12 univalent ions (alkali metal, ammonium, halide, nitrate, and perchlorate) and five divalent ions (alkaline earth and sulfate) in water at 125, 150, 175, and 200 °C and at 2 MPa were derived from the data of Ellis. Similar data for NH(4)(+) and NO(3)(-) at 0-100 °C, not included in Part 4, were added, derived from his data too. The (negative) electrostrictive volumes, ΔV(elstr)(i,T), of these ions at infinite dilution were obtained from the shell-by-shell calculation of the electrostriction according to Marcus and Hefter that takes into account the mutual dependence of the relative permittivity of the water around the ion and the electrical field strength at it.

The standard partial molar volumes of ions in solution. Part 4. Ionic volumes in water at 0-100 degrees C.

The standard partial molar volumes of 10 univalent and 5 divalent ions in water over the temperature range of its existence as a liquid at ambient pressure (0-100 degrees C) are fitted as the sum of their (negative) electrostrictive volumes and intrinsic volumes, including disordered water. The former are obtained from the shell-by-shell calculation of the electrostriction according to Marcus and Hefter that takes into account the mutual dependence of the relative permittivity and the electrical field strength of the water around the ion. This calculation yields also the spatial extension of the dielectrically saturated region around the ions.

Electrostriction, ion solvation, and solvent release on ion pairing.

The theoretical mean molar electrostriction volume of electrolytic solvents, DeltaVel(solvent), was calculated from their properties: the relative pressure derivatives of the density (the compressibility) and permittivity and their second pressure derivatives. The molar electrostriction caused by ions at infinite dilution was taken as the differences of their standard partial molar volumes in the solution and their intrinsic volumes: DeltaVel(ion) = Vinfinity(ion) - Vin(ion). The ratio ninfinity = DeltaVel(ion)/DeltaVel(solvent) then represents the solvation number of the ion in the solvent at infinite dilution.

Ionic volumes in solution.

The volumetric properties of electrolytes in solutions indicate the interactions of the constituent ions with their environment: the solvent and other ions. The interactions with the solvent alone are manifested at infinite dilution by the standard partial molar volume, V(infinity)(salt), obtained from density measurements. To study the interactions, it is necessary to split V(infinity)(salt) into the additive ionic contributions, V(infinity)(ion), using an extra-thermodynamic assumption.

The connection between in vitro water uptake and in vivo skin moisturization.

Background/purpose: Humectancy or hygroscopy is the water absorption tendency of a substance from the surroundings. Our interest, from the clinical point of view, consists of correlating this tendency in vitro and its effect in vivo for the development of drugs and formulations for the treatment of dry skin syndrome or diseases accompanied by dry skin.

Method: In vitro, water absorption was measured using the comparative isopiestic method.