Molar volume solvent

The solvent triangle classification method of Snyder Is the most cosDBon approach to solvent characterization used by chromatographers (510,517). The solvent polarity index, P, and solvent selectivity factors, X), which characterize the relative importemce of orientation and proton donor/acceptor interactions to the total polarity, were based on Rohrscbneider s compilation of experimental gas-liquid distribution constants for a number of test solutes in 75 common, volatile solvents. Snyder chose the solutes nitromethane, ethanol and dloxane as probes for a solvent s capacity for orientation, proton acceptor and proton donor capacity, respectively. The influence of solute molecular size, solute/solvent dispersion interactions, and solute/solvent induction interactions as a result of solvent polarizability were subtracted from the experimental distribution constants first multiplying the experimental distribution constant by the solvent molar volume and thm referencing this quantity to the value calculated for a hypothetical n-alkane with a molar volume identical to the test solute. Each value was then corrected empirically to give a value of zero for the polar distribution constant of the test solutes for saturated hydrocarbon solvents. These residual, values were supposed to arise from inductive and... 

Solvent Molar volume saturation Solvent) Sb Iodine)... 

The parameters y, and K12 are independent of the solvent. Thus, for a molecule moving as a single unit, (Y 2 )/K12 should be a linear function of the molar volume of the liquid solvent at 0°K, V (0). An average value of the solvent molar volume at 0°K was calculated using the methods of Sudgen and Biltz (Table II). A graph of... 

Solvent Molar Volume Un/cm mor Enthalpy of Vaporization kJ mor Internal Pressure A/kJ dm ... 

The electroscatic terms AG°r,c are calculated in straightforward fashion via Eq. (5), as shown in column 5 of Table 6. In the calculation, one must assign the thickness r — r of the electrostricted layer. Following Abraham and Liszi [131], we equated the thickness to the average radius of a solvent molecule r.s, estimated from the solvent molar volume (Vs) ... 

Figure 1 Electrostatic and neutral contributions to the standard molar Gibbs energy of transfer of univalent cations from water to solvents having five different dielectric constants, calculated from the single-layer electrostatic model. Calculations are valid for 25°C and assume a hypothetical constant solvent molar volume of 100 cm /mol. Solid lines correspond to the electrostatic term AGtr.ii [from Eqs. (5) and (18)] and the dashed line corresponds to the neutral term A C r.m.-ui [Eq. (26)]. Radii of the alkali metal ions are indicated along the X-axis (Table 2).

Figure 2 shows the effect of the solvent molar volume on AG°,c for a single dielectric constant value, es = 10. It may be seen that becomes more positive when V,s is increased. Moreover, the bias toward large ions also increases. Negative values of AG°r,ci re mathematically allowed for solvent molar volumes smaller than that of water, an unexpected condition. 

In the preceding section, factors that were theoretically connected with ion-transfer processes included ion radius, solvent dielectric constant, and solvent molar volume. Failure to account totally for the standard molar Gibbs transfer energies led to the suggestion that donor-acceptor properties of the solvent could be used to augment the electrostatic approach. In this section, we briefly describe statistical approaches that have been employed to elucidate the major factors governing ion transfer. The approaches that will be treated here rely on linear solvation energy relationships of the form... 

Ratio of polymer molar volume to solvent molar volume Number of segments in the primitive path... 

Among the factors that determine the permeation of organic solvents, Bhanushali et al. [22] included the solvent molar volume, surface energy, and sorption. 

The value of /if of a solute is a function of its activity coefficients in the two phases and of the solvent molar volumes [Eq. (5)]. Thus, K depends on the type of the solvent system as well as the solute concentration and temperature. For a given solvent-water and temperature, K is constant for a solute only at low-solute concentrations when y and V approach constant values. The variation of y with the solute concentration for the two components of a binary solution may be characteristically described by van Laar equations (72, 102, 103) ... 

The temperature dependence may be evaluated by partial differentiation of Eq. (5) with respect to temperature. With dilute solute concentrations, the change of the solvent molar volume with a small temperature increment would be insignificant, and the variation of K with temperature is given as ... 

Figure .1.3. Parameter vs. solvent molar volume. 1 -methanol, 2 - acetone, 3 - methyl acetate, 4 - ethyl acetate, 5 - propyl acetate, 6 - benzene, 7 - toluene, 8 -ethylbenzene. [Adapted, by permission, from D Amauld, R L Laurence, Ind. Eng. Chem. Res., 31(1), 218-28(1992).]...

Reddy and Doraiswamy, 1967 (24] modified equation (1.18) by replacing the association factor in this equation for the square root of the solvent molar volume, they proposed... 

Here (f>i and 2 are the polymer and solvent volume fractions respectively, Vf and V2 are the polymer and solvent molar volumes, and x is the Flory-Huggins interaction parameter between polymer and solvent. 

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