Empirical Setschenow Constant Data

Empirical expressions have been reported for presenting the Setschenow constants for a large variety of solutes and ions. Weisenberger and Schumpe [63] presented an expression for gaseous solutes that do not interact chanicaUy with the solvents (excluding, e.g., NHj, HCl, and CO in aqueous solutions)  

The summation extends over all the ionic species present in the (aqueous) solution, including cases of electrolyte mixtures, is an ion-specific parameter, relatively 

Because of the proportionality in Equation 7.37, the values are valid down to infinite dilution, hence should be additive with respect to the individual ions. Conventional ionic values of based on the convention that (H, aq) = 0 and on the basis that also k (O ) = 0, have been reported [63], as weU as values of and for several gases. The values of pertaining to the salting of at 25°C, are reproduced in Table 7.6 and are approximately proportional to the charge numbers of the ions—for 19 cations =0.080 0.002 (Na and Ba are outliers) and for 

25 anions k i/z = -0.072 0.007. Mthin this approximate proportionality, the diminish with increasing sizes of the ions. The values of generally increase with 

Xie et al. [66] reported the salting constants for benzene in aqueous electrolyte solutions, g, and on the basis of the convention that (H, aq) = 0 ionic values could be obtained from the data, as shown in Table 7.6. It is noted that several ions have a salting-in effect iodide and perchlorate mildly and tetraalkylammonium ions strongly. Similar constants have also been reported by Xie et al. [64, 66] for other organic compounds, and several theories have been explored in order to systematize these constants. 

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