Henry’s law, solubility coefficient

CrystallinitY, Fillers, and Morphology. The solubility of low molecular weight compounds is extremely small in the crystallites of polymers in comparison to that in the amorphous regions of the same polymer (15). Thus, equilibrium sorption in semicrystalline polymers is less than that for corresponding completely amorphous ones. For the same reasons crystalline polymers are more chemical resistant than amorphous ones. As a good approximation for gases, the Henry s law solubility coefficient of a semicrystalline polymer is related to that for the same polymer in the amorphous state, S, by the following ... 

In the relation (1), k m the Henry s law solubility coefficient for molecular hydrogen in the crystal. Experiment showed (12) that equation (1) was correct, so that hydrogen is both dissolved as molecules and diffuses as molecules. The derived value for D was 2-3 x 10 " cm. sec. at 680° C. 

C -.Langmuir sorption capacity cm STP/cm polym. kp Henry s law solubility coefficient cm STP/ (cm polym. cmHg). b affinity constant of Langmuir site cmHg... 

De Bruyn, W. J., E. Swartz, J. H. Hu, J. A. Shorter, P. Davidovits, D. R. Worsnop, M. S. Zahniser, and C. E. Kolb, Henry s Law Solubilities and Setchenow Coefficients for Biogenic Reduced Sulfur Species Obtained from Gas-Liquid Uptake Measurements, . /. Geophys. Res., WO, 7245-725 f (f995). 

The large S02 mass accommodation coefficient (7 - 0.11) indicates that interfacial mass transport will not limit the rate of S02 uptake into clean aqueous cloud and fog droplets. Either gas phase diffusion, Henry s law solubility, or aqueous reactivity will control the overall rate of aqueous S(IV) chemistry. This conclusion is demonstrated by modeling studies of S02 oxidation in clouds by Chamedies (3) showing that the conversion time of S(FV) to S(IV) is independent of the mass accommodation coefficient for 1 7 > 10 2 Schwartz (1 ) has also shown that, with 7 as large as our measured value, the interfacial mass transport is unlikely to inhibit the oxidation of SC by or Ho02 in cloud droplets for gas concentrations typical of non-urban industrialized regions. 

Laplace transform of C axial dispersion coefficient, m /s Henry s law solubility constant, Cl/Cq. adsorption equilibrium constant radial distance in the catalyst particle, radius of the catalyst particle Laplace transform variable t ime, s. 

Stem and coworkers have shown that deviations from constant diffusion coefficient behavior generally occur in rubbery polymers before the onset of deviations from Henry s Law solubility behavior. In either case, substitution of Eq. (20.4-6) along with the appropriate isotherm form into Eq. (20.3-2) permits graphical or analytical integration to obtain the permeability in terms of the upstream and downstream penetrant volume fractions or concentrations. Even for the case in which Henry s Law applies, the resulting expression is rather complicated and is not reproduced here in its general form. 

The uptake coefficient need not be constant with time. A heterogeneous interaction on a solid surface could result in the adsorbate or its reaction products accumulating on the surface. This could lower the number of available surface sites and thereby decrease the net uptake coefficient. On liquid surfaces, solubility limitations can lead to time-dependent uptake coefficients. As the surface layer of the liquid saturates with gas, re-evaporation starts to compete with adsorption and the net uptake coefficient decreases with time. The time-dependence of the uptake coefficient can be analyzed to yield the effective Henry s law solubility. 

DJD is the ratio of the diffusion coefficients of the two molecules and can be viewed as the mobil-ity or diffusivity selectivity, reflecting the different sizes of the two molecules is the ratio of the Henry s law sorption coefficients of the two molecules and can be viewed as the sorption or solubility selectivity of the two molecules. The balance between the solubility selectivity and the diffusivity selectivity determines whether a membrane material is selective for molecule A or molecule B in a feed mixture. Either the diffusivity or the solubility needs to be enhanced to increase membrane selectivity however, polymers that are more permeable are generally less selective and vice versa [19]. The schematic diagram of polymer membrane is given in Figure 6.1. The driving force behind the transport process which involves sorption, diffusion and permeation is the concentration difference between the two phases [21]. 

Sorption of solvents through the membrane depends much more on Langmuir sorption than on Henry s Law. Solubility of solvent in membrane is usually very small (less than 1%). The permeability coefficients of solvents correlate with the longest molecular dimension of solvents. The permeation flux through the film is given by the following equation ... 

Principles of Rigorous Absorber Design Danckwerts and Alper [Trans. Tn.st. Chem. Eng., 53, 34 (1975)] have shown that when adequate data are available for the Idnetic-reaciion-rate coefficients, the mass-transfer coefficients fcc and /c , the effective interfacial area per unit volume a, the physical solubility or Henry s-law constants, and the effective diffusivities of the various reactants, then the design of a packed tower can be calculated from first principles with considerable precision. 

As most organotins decompose, boiling points of 250 °C were assumed in the absence of a "true boiling point. The values for Henry s law constant and organic carbon/water partition coefficient were all derived from EUSES unless otherwise indicated. The chlorides were chosen as soluble salts in this table toxicity is independent of salt (see section 8), and soluble salts maximize likely environmental exposure, giving worst case in modelling environmental fate. 

Adsorption of a fluid quantified by the surface solubility coefficient according to Henry s law... 

The interrelationships of the various coefficients associated with fluid uptake (Section 23.4.2) mean that it should be possible to estimate a rate for one of the uptake phenomena from test data for another of them. Campion proposed using this approach to estimate permeation coefficient Q from solubility coefficient s. The form of a liquid absorption plot (Figure 23.6, Section 23.4.4.1) is such that s should be obtainable from it, and inspection showed that this link was via Henry s law with concentration corrected by the polymer density p. The following expression was derived for s ... 

Many subtleties associated with ED, for instance, accompanying thermodynamic cooling issues, failure processes, and effects of localized stresses, are discussed in detail in the extensive review on this topic by Briscoe et al. Other workers have observed similar fracture effects arising from rapid temperature increases while maintaining pressure the connection with ED is via Henry s law linking dissolved gas concentration and solubility coefficient, and the fact that solubility coefficient decreases (in an Arrhenius fashion, as it happens) for readily condensable (i.e., less volatile) gases when temperature increases. 

DNAPLs have higher densities than water, most between 1 and 2 g/mL, some are near 3 g/mL, for example, bromoform, which has a density of 2.89 g/mL. They have limited water solubilities, and are usually found as the free-phase immiscible with water or as residuals trapped by soil. Most DNAPLs are volatile or semivolatile Pankow82 has listed information on their physical and chemical properties, such as molecular weight, density, boiling points, solubility in water, vapor pressure, sediment/water partition coefficient, viscosity, Henry s law constant, and so on (see Tables 18.8 and 18.9). 

The solubility of gases varies widely. Gases with a low solubility (e.g. N2, O2) have large values of the Henry s Law coefficient. This means that the liquid-film resistance in Equation 7.6 is large relative to the gas-film resistance. On the other hand, if the gas is highly soluble (e.g. CO2, NH3), the Henry s Law coefficient is small. This leads to the gas-film resistance being large relative to the liquid-film resistance in Equation 7.6. Thus,... 

If a2/ax = gim2lgxmx m2/mx (a = activity, g = molal activity coefficient, m = molality) if Henry s law is obeyed and a = gm, mh and m2 are the molal solubilities of the polymorphs, and if the standard molar enthalpies and standard molar entropies of solution are, respectively,... 

Physical and Chemical Properties. Most of the important physical-chemical properties of acrylonitrile have been determined (see Chapter 3). However, the partitioning of acrylonitrile between the air and water has been evaluated by using an estimated value for a Henry s law constant. This general approach assumes that the concentration of the chemical in water is low. Because acrylonitrile is relatively soluble in water, this approach may not be accurate. Experimental measurement of the partition coefficient for acrylonitrile at water-air interfaces would be useful in refining models on the behavior of acrylonitrile in the environment. 

When solubility and vapor pressure are both low in magnitude and thus difficult to measure, it is preferable to measure the air-water partition coefficient or Henry s law constant directly. It is noteworthy that atmospheric chemists frequently use Kwa, the ratio of water-to-air concentrations. This may also be referred to as the Henry s law constant. 

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. 

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