Solvation constant

The electrical conductivities of electrolyte solutions and the ion-pair association constant are both very sensitive to ion solvation and permit the calculation of solvation constants. 

Once the water-rich region is passed, the B values all rise strongly. The interpretation of this rise in terms of the change in hydrodynamic volume of the ions seems reasonable. The extraction of a preferential solvation constant from it is perhaps a bit shaky in each individual case, but taken together they tend to confirm the original expectation. The values of K and corresponding values of AG°, derived from the B coefficients, are recorded in Table III. They are sufficiently uncertain that they all must be considered equal within experimental error, i.e., K = 0.5 0.2, AG° = 1.6 0.8 J mol"1. That is, all these salts appear to show a slight preference for water over methanol. 

Figure 6 Log (rate constant for dissolution) plotted versus log (solvation constant). Dissolution rates at pH 2 or rate constants at pH 0 are plotted for different compositions of orthosilicate as indicated. References cited in text.

Clearly, the adhesion community should consider the LSER approach when IGC characterization of material surfaces is concerned. The price to pay, however, is to use a large number of solutes, at least 20-30 probes (parameters are available for 2000 organic molecules [133]), to derive accurately five solvation constants for the sorbents under test. 

A further discrepancy was noted in 5.5.3.2, where we saw that some of the solvation constants evaluated from surface tension data did not agree closely with the corresponding numbers found in solubility studies. 

The curvature correction factor g is dimensionless, as are the solvation constants K, andK. The parameter gA is expressed in molecule by giving the surface tension the units J (where 1 erg em = 1 x 10 J... 

The effect of asphaltenes on the physical properties of heavy oils and bitumen has been studied extensively. It has been demonstrated that the viscosity of petroleum is significantly influenced by the presence and concentration of asphaltenes. Storm et al. demonstrated that when the relative viscosity of heavy oils was plotted versus asphaltenes concentration in both toluene (at room temperature) and vacuum residue (at 93°C), a straight line resulted. Thus, it was concluded that toluene is as good a solvent for asphaltenes as for vacuum resid. However, the amount of solvation is temperature dependent. By analyzing the temperature dependency of solvation. Storm et al. showed that the forces holding asphaltenes in the resid are very weak. Moreover, the fact that the solvation constant is the same for toluene at 25 °C as in a vacuum resid at 93°C implies that the forces between asphaltene colloidal particles and toluene are weaker. 

Values of 5x (,j>0, that is, when A is enriched in the environment of P with respect to its bulk composition, mean that the ion is preferentially solvated by A and its negative values denote the preferential solvation of P by B. A further way to express the preferential solvation is by means of the preferential solvation constant ... 

Table 8.2.3. Empirical relationships for estimating solvation constants...

In this theory the general medium and solvation effects are coupled through the solvation exchange constants K, and K2, which determine the composition of the solvation shell surrounding the solute, and thereby influence the surface tension in the solvation shell. But the situation is actually more complicated than this, for if surface tension-composition data ate fitted to eq. [8.2.26] the resulting equilibrium constants are not numerically the same as the solvation constants Kj and K2 evaluated from a solubility study in the same mixed solvent. Labeling the surface tension-derived constants K j and K 2, it is usually... 

---