Henry’s law and

Substances at high dilution, e.g. a gas at low pressure or a solute in dilute solution, show simple behaviour. The ideal-gas law and Henry s law for dilute solutions antedate the development of the fonualism of classical themiodynamics. Earlier sections in this article have shown how these experimental laws lead to simple dieniiodynamic equations, but these results are added to therniodynaniics they are not part of the fonualism. Simple molecular theories, even if they are not always recognized as statistical mechanics, e.g. the kinetic theory of gases , make the experimental results seem trivially obvious. 

Fugacity in Liquid Mixtures Raoult s Law and Henry s Law Each component in a liquid mixture has an equilibrium vapor pressure, and hence, a vapor fugacity. These fugacities are functions of the composition and the nature of the components, with the total vapor fugacity equal to the sum of the fugacities of the components, That is,... 

The kinetics of transport depends on the nature and concentration of the penetrant and on whether the plastic is in the glassy or rubbery state. The simplest situation is found when the penetrant is a gas and the polymer is above its glass transition. Under these conditions Fick s law, with a concentration independent diffusion coefficient, D, and Henry s law are obeyed. Differences in concentration, C, are related to the flux of matter passing through the unit area in unit time, Jx, and to the concentration gradient by,... 

These relationships are alternative expressions of Raoult s and Henry s laws. Raoulhan and Henrian behaviours of a component in a solution, in terms of activity, are shown schematically in Figure 3.7. 

Physical data important for describing environmental behavior (Koc, Kow, vapor pressure, water solubility, and Henry s law constant) are incomplete. In general, hydraulic fluids have relatively low water solubilities. 

The log Kow, water solubilities, and Henry s law constants of several of the components that are present in the organophosphate ester hydraulic fluids included in this profile have been measured and are presented in Tables 3-4, 3-5, 3-8, and 3-9. In general, chemicals with low Kow (log Knw <1) tend to have high water solubilities, do not sorb to sediments, and do not bioconcentrate chemicals with high Kow tend to have low water solubilities, partition to sediments and soil, and bioconcentrate in fish (Lyman et al. 1982). Most of the values presented above are for mixtures and are the average values for all of the components in the mixture. 

FIGURE 24.3 Relative solubility and Henry s law constants for selected fuel oxygenates. (Adapted from U.S. EPA, Technologies for Treating MTBE and Other Fuel Oxygenates, EPA 542-R-04-009, United States Environmental Protection Agency, Washington, DC, May 2004.)... 

Accordingly, plots are presented at the end of each chapter for solubility, vapor pressure, Kow, and Henry s law constant versus Le Bas molar volume. 

The calculation is illustrated in Table 1.5.5 for pentachlorophenol. The experimental aqueous solubility is 14.0 g/m3 at a pH of 5.1. The environmental pH is 7. Higher environmental pH increases the extent of dissociation, thus increasing the Z value in water, increasing the apparent solubility, decreasing the apparent KqW and Henry s law constant and the air-water partition coefficient, and decreasing the soil-water partition coefficient. 

Dunnivant, F. M., Elzerman, A. W., Jurs, P. C., Hansen, M. N. (1992) Quantitative structure-property relationships for aqueous solubilities and Henry s law constants of polychlorinated biphenyls. Environ. Sci. Technol. 26, 1567-1573. 

Tse, G., Orbey, H., Sandler, S. I. (1992) Infinite dilution activity coefficients and Henry s law coefficients for some priority water pollutants determined by a relative gas chromatographic method. Environ. Sci. Technol. 26, 2017-2022. 

Reported vapor pressures and Henry s law constants of ethylcyclohexane at various temperatures and the coefficients for the vapor pressure equations... 

Reported aqueous solubilities and Henry s law constants of 1,2,3-trimethylbenzene at various temperatures... 

FIGURE 3.1.1.7.1 Logarithm of mole fraction solubility and Henry s law constant versus reciprocal temperature for 1,2,3-trimethylbenzene. 

De Maagd, P.G.-J., ten Hulscher, T.E.M., Van den Heuvel, H., Opperhuizen, A., Sijm, D.T.H.M. (1998) Physicochemical properties of polycyclic aromatic hydrocarbons aqueous solubilities, n-octanol/water partition coefficients, and Henry s law constants. Environ. Toxicol. Chem. 17, 252-257. 

Passivirta, J., Sinkkonen, S., Mikkelson, P., Rantio, T., Wania, F. (1999) Estimation of vapor pressures, solubilities and Henry s law constants of selected persistent organic pollutants as functions of temperature. Chemosphere 39, 811-832. 

In the following, the Raoultian and Henrian standard states will be presented. These two are the far most frequent standard states applied in solution thermodynamics. Before discussing these standard states we need to consider Raoult s and Henry s laws, on which the Raoultian and Henrian standard states are based, in some detail. 

Organic compounds released into the vadose zone exist in four closely interrelated forms free-phase NAPL, attenuated to surface of soil grains, dissolved in water retained on and between the soil particles, and present as a gaseous phase. The mass distribution of each of these phases is controlled by such factors as concentration gradients, distribution coefficients, and Henry s law constants. 

Yoo KP, Lee SY, Lee WH. 1986. Ionization and Henry s Law constants for volatile, weak electrolyte water pollutants. Korean J Chem Eng 3 67-72. 

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