Regular solution constant

These expressions can be simplified since the activity coefficient in the particular case of a regular solution can be expressed by the regular solution constant 2 through eqs. (3.84) and (3.85) ... 

Here Q is the regular solution constant and xSiB the fraction of Si atoms in silicon state B. By noting that xSiA =1 - xSi B, equation (5.31) becomes... 

Regular Solution Theory. The key assumption in regular-solution theory is that the excess entropy, is zero when mixing occurs at constant volume (3,18). This idea of a regular solution (26) leads to the equations ... 

This model is appropriate for random mixtures of elements in which tire pairwise bonding energies remain constant. In most solutions it is found that these are dependent on composition, leading to departures from regular solution behaviour, and therefore the above equations must be conhned in use to solute concentrations up to about 10 mole per cent. 

For a given reaction studied in a series of solvents, (8r- 8 f) is essentially constant, and most of the change in In k will come from the term — AV (8j — 8s)". If AV is positive, an increase in 8s (increase in solvent internal pressure) results in a rate decrease. If AV is negative, the reverse effect is predicted. Thus reactivity is predicted by regular solution theory to respond to internal pressure just as it does to externally applied pressure (Section 6.2). This connection between reactivity and internal pressure was noted long ago," and it has been systematized by Dack. -" ... 

The Flory-Huggins interaction parameter, x Is the sum of enthalpic (xH) and entropic (x ) contributions to the polymer-solute interactions (28). xs is an emPitical constant related to the coordination of the polymer subunits (29). Chiou et al. (20) have selected a value of 0.25 for xs of humlc matter. From regular solution theory, xq is given by... 

To the donor cell, 3 mL of the model drug solution was added, and to the receptor half-cell 3 mL of the solvent was added. Timing of the diffusion of the solute began as soon as both half-cells were filled. At regular intervals (i.e., 15, 30, and 60 minutes) the contents of the receptor cell were moved and replaced with fresh solvent, which in this case was pH buffer solution. To ensure constant temperature of the iimer cell solution, constant-temperature water was pumped through the outer half-cells. 

Fig. 4. 23 Application of the regular solution theory for correlation of distribution constants for ZnA2 and CuA2 with solvent properties (solubility parameters) the numbers refer to the solvents listed in Table 4.10. (From Ref. 22.)...

The interaction parameter, ft, is a fitting parameter in the regular solution model that can be found from liquid-solid equilibrium data (93). With the DLP model, the interaction parameter is calculated from the lattice parameters of the binary compounds. For a compound semiconductor AiJB C, ft is computed from the lattice constants aAC and aBC of the binary compounds from the following expression... 

The Chao-Seader and the Grayson-Streed methods are very similar in that they both use the same mathematical models for each phase. For the vapor, the Redlich-Kwong equation of state is used. This two-parameter generalized pressure-volume-temperature (P-V-T) expression is very convenient because only the critical constants of the mixture components are required for applications. For the liquid phase, both methods used the regular solution theory of Scatchard and Hildebrand (26) for the activity coefficient plus an empirical relationship for the reference liquid fugacity coefficient. Chao-Seader and Grayson-Streed derived different constants for these two liquid equations, however. 

Reduced parameters, 66-69 Refractive index (RI) detector, 206-207 Regular solution, 49 Relative retention, 20-21, 22, 77 Repeatability, see Precision Reproducibility, see Precision Resolution, 17-19, 55 Response factors (detector), 104, 125 Response time, 94 Retardation factor, Rf, 71 Retention index of Kovats, 78 Retention ratio, 11, 12, 71 Retention time, 6, 9 Retention volume, 9, 75 adjusted, 10, 75 corrected, 62-63, 75 net, 63, 75 specific, 110 Reverse phase LC, 158 Rohrschneider/McReynolds constants, 137-140... 

Related Calculations. The regular-solution model of Scatchard and Hildebrand gives a fair representation of activity coefficients for many solutions containing nonpolar components. This procedure is suggested for estimating vapor-liquid equilibria if experimental data are not available. The solubility parameters and liquid molar volumes used as characteristic constants may be obtained from Table 1.10. For substances not listed there, the solubility parameters may be calculated from heat of vaporization and liquid molar volume data as shown in step 4. 

According to the regular solution theory, the dimerization constant of copper(II) decanoate, ditn, described above can be written as follows (142, 151) ... 

It was found that the humic material ion exchange properties can be explained by a regular solution model similar to that of Truesdell and Christ (16) for clays. The thermodynamic constants for the exchange reactions studied were found to be different for each ionic strength. Changes in the configurations of the organic molecules could cause the observed variations. Other evidence (17,... 

Like van der Waals, Cahn and Hilliard also elaborated their theory. Close to the critical point they confirmed van der Waals 3/2 power in 2.5.29, but with a reinterpreted constant. Their profile also obeyed the tanh law 2.5.31 and they applied the regular solution theory (see sec. 1.2.18c) to obtain quantitative values for the surface tension. In table 2.1 some results are collected for simple liquids for which this theory is supposed to apply. These data give some feeling for the achievements. 

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