Ion partition coefficient

Negative decadic logarithm of the relative activity of H3O+ ions Partition coefficient... 

Omitted from this elementary theory are effects of plasticizer and ion pairing. Ion pair formation constants in the organic phase increase with decreasing dielectric constants of the plasticizer, in the absence of specific bonding effects. In the more general theory the single ion partition coefficients are replaced by the product of partition coefficient and ion pair formation constant. 

On a brighter side, the model of Kretz (1982) for the partitioning of cations between calcite and dolomite has shown impressive correlations between observational data and predicted partition coefficients (see Table 3.2). He proposes, based on the earlier work of Jacobsen and Usdowski (1976), that different partition coefficients exist for a trace cation at Mg and Ca sites in dolomite, which are principally influenced by the size differences between the trace cation and calcium or magnesium. He has made a number of predictions of metal ion partition coefficients in dolomite. It will be interesting to see if future work bears them out. 

The geometry of real polymer membranes still induces some problems with quantitative application of model calculations, and calibration procedure remains more or less empiric. However, the model systems imitating membranes, the interfaces of two immiscible electrolyte solutions (ITIES), are free from this shortcoming. Various types of LJP behavior for ITIES dependent on the ratios of ion partition coefficients are considered in ref. [95] remarks in ref. [96] are also useful. The effect of initial concentration distribution on the temporal LJP behavior is considered in ref. [97] self-consistently for the limiting cases of thick membranes (assumed to operate as ion-selective electrodes) and thin membranes (assumed to imitate biological membranes). 

Thus equation (26) relates the measured ion partition coefficient and the free solution concentration to the charge concentration in the gel. 

If the ions are ordered from the highest to lowest values of the single ion partition coefficients a series can be derived for both the cation and anions describing their affinity for the interface. For the anions the series is CIO4 = SCN > CIO3 > Acetate > I > NO3 > Br > Cl > F > CO > With the exception of acetate, this series... 

Fig. 9. Comparison of measured surface tension gradients for equimolar mixtures of pairs of electrolytes with calculated values of the surface tension gradient using the ion partition coefficients of Pegram and Record.

Also, as the ion partition coefficients apply to mixed electrolyte systems and the behavionr of mixed electrolyte systems is not predicted by measurements of the surface tension, we can state that the partitioning of the ions at the interface controls bubble coalescence through a mechanism other than the surface tension. 

The influence of electrolytes on bubble coalescence in both aqueous and non-aqueous systems is ion specific. The available evidence suggests that ion specific effects at the air-water interface are strongly correlated with the partitioning of ions in the interfacial region. Ion partition coefficients determined from surface tension data correlate well with the empirically assigned a and parameters used to predict bubble coalescence inhibition. Bubble coalescence is inhibited when there is an accumulation of both ions at the interface or a removal of both ions from the interface, though the precise mechanism of inhibition remains elusive. 

The ion partition coefficients are also correlated with the Hofmeister series (with some exceptions such as acetate). Therefore, there is now a substantiated link between the ion specific effects observed at the air-water interface and the more ubiquitous Hofmeister-type specific ion effects. It is clear that specific ion effects are manifested at the surface and determined by the relative affinity of different ions for an interface. 

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