Molar water solubilities, correlations partition coefficients

The binding constants of a number of compounds were measured using dialysis, solubility and sorption techniques. The solubility technique was used for compounds which were not radiolabeled. All data was collected at pH = 8.3. The binding constants were then compared to the octanol/water partition coefficients for the compounds and the molar solubilities of the compounds. The data is presented in Table II. The Kow values were taken from the literature.18 22-2 The solubility values were determined in this research with the exception of DDT and Lindane, which were taken from the literature. A plot of log Kc vs. log Kow is presented in Figure 5. The slope of this line is 0.71, the intercept is 0.75 and the value of the correlation coefficient is 0.9258. The regression is highly significant... 

In the multimedia models used in this series of volumes, an air-water partition coefficient KAW or Henry s law constant (H) is required and is calculated from the ratio of the pure substance vapor pressure and aqueous solubility. This method is widely used for hydrophobic chemicals but is inappropriate for water-miscible chemicals for which no solubility can be measured. Examples are the lower alcohols, acids, amines and ketones. There are reported calculated or pseudo-solubilities that have been derived from QSPR correlations with molecular descriptors for alcohols, aldehydes and amines (by Leahy 1986 Kamlet et al. 1987, 1988 and Nirmalakhandan and Speece 1988a,b). The obvious option is to input the H or KAW directly. If the chemical s activity coefficient y in water is known, then H can be estimated as vwyP[>where vw is the molar volume of water and Pf is the liquid vapor pressure. Since H can be regarded as P[IC[, where Cjs is the solubility, it is apparent that (l/vwy) is a pseudo-solubility. Correlations and measurements of y are available in the physical-chemical literature. For example, if y is 5.0, the pseudo-solubility is 11100 mol/m3 since the molar volume of water vw is 18 x 10-6 m3/mol or 18 cm3/mol. Chemicals with y less than about 20 are usually miscible in water. If the liquid vapor pressure in this case is 1000 Pa, H will be 1000/11100 or 0.090 Pa m3/mol and KAW will be H/RT or 3.6 x 10 5 at 25°C. Alternatively, if H or KAW is known, C[ can be calculated. It is possible to apply existing models to hydrophilic chemicals if this pseudo-solubility is calculated from the activity coefficient or from a known H (i.e., Cjs, P[/H or P[ or KAW RT). This approach is used here. In the fugacity model illustrations all pseudo-solubilities are so designated and should not be regarded as real, experimentally accessible quantities. 

Physical-Chemical Properties of Chlorinated Dibenzo-p-dioxins Reported and experimental data for aqueous solubility, octanol-water partition coefficient, vapor pressure, and Henry s law constant are compiled and correlated with molar volumes and chlorine number. 

All that which has been said about empirical models based on the 1-octanol/water partition coefficients is also true for models based on the water solubilities (a) the measured water solubility data are of low precision (see TABLE 4), (b) there exists a wide variety of quantitative linear models correlating soil sorption coefficients and water solubility (Wijayaratne and Means 1984 Chiou et al. 1983 Banwart et al. 1982 Means et al. 1982 Briggs 1981 Kenaga and Goring 1980 Karickhoff etal. 1979), and (c) the statistical requirements for linear regression models are violated by the large errors in the experimental water solubility data. That some quantitative models (Wijayaratne and Means 1984 Banwart et al. 1982 Means et al. 1982) use non-molar units ( ig mL ) for water solubility data, further impedes their use. 

Chlorinated aromatic hydrocarbons, congeneric series, chlorobenzenes (CBs), polyclorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs), solubility, vapour pressure, octanol/water partition coefficient, Henry s law constants, correlations, chlorine number, molar volume. 

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