Bockris and Saluja

Bockris and Saluja applied these equations derived by Debye to a number of electrolytes and, using data that included information provided by Conway and by Zana and Yeager, calculated the difference of the solvation numbers of the ions of salts. The relevant parameters are given in Table 2.6. 

Swift and Sayne used concepts similar to those of Bockris and Saluja if a molecule stays associated with an ion for more than the time needed for a diffusional jump, it counts as a primary hydration number. This approach yields approximately 4 solvation molecules for and Ca ", and 5 for Ba and Sr", whereas nonspectroscopic methods for these systems yield values that are two to three times larger. Does NMR measure only water arranged in a first, octahedral layer in the first shell near the ion and is it insensitive to the rest of the water structure near an ion ... 

The entropy of solvation values reflect solvational structure near an ion. The following discussion of models that are more in agreement with the experimental values of solvational entropies follows the seminal treatment due to Bockris and Saluja in 1982. Models for the region near an ion are shown in Fig. 2.37. The entropy of hydration from the model with no SB region was 170 to 250 J mol" lower (more negative) than the experimental values, and was therefore not pursued further. 

Bockris and Reddy, and the structure of the solvation shell, 119 Bockris and Saluja... 

In the 1970s Bockris and Saluja developed models incorporating and extending ideas proposed by Eley and Evans, Frank and Wen, and Bockris and Reddy. Three basic models of ionic hydration that differ from each other in the structure in the first coordination shell were examined. The features of these models are given in Table 2.16. The notations chosen for the models wo-e lA, IB, 1C 2A, 2B, 2C and 3A, 3B, 3C, where 1, 2, and 3 refer to three basic hydration models, and A, B, and C refer to the subdivision of the model for the structure-broken (SB) region. These models are all defined in Table 2.16. A model due to Bockris and Reddy (model 3 in Table 2.16 and Fig. 2.37) recognizes the distinction between coordination number (CN) and solvation number (SN). 

Gusev assumed that the point of intersection indicates the absence of free (i.e., non-solvating) water, so there is minimal proton transport through the solution. The water cation mole ratio at that point is presumably the hydration number of the cation, including both primary and secondary solvation. This method gave a value of h = 20 for Th(IV) which can be compared to the value of 22 obtained from compressibility measurements (Bockris and Saluja 1972a, b, 1973) based on the lower compressibility of solvated solvent molecules (Passynski 1938) as a result of electrostriction. 

Another consequence of the ionic electric field is the large compressive pressure that it exerts on the solvent near the ion. Bockris and Saluja [62] calculated the effective pressure in the middle of the first hydration shell of aqueous ions, the numerical coefficient being valid at 25°C with the radii in nanometer ... 

J. O M. Bockris and P. P. S. Saluja, Hydration Numbers for Partial Molar Volumes and Vibrational Potentials from Solutions, J. Phys. Chem. 76 2140 (1972). 

---