Limiting activity coefficient

Two limiting activity coefficients can be obtained from Eq. (1.3.44) for each electrolyte ... 

Dohnal, V., Hovorka, S. (1999) Exponential saturator A novel gas-liquid partitioning technique for measurement of large limiting activity coefficients. Ind. Eng. Chem. Res. 38, 2036-2043. 

This shows that knowledge of the vapor pressure of A and its limiting activity coefficient allows us to calculate the Henry s law constant.7... 

Thus the free energy of solvation may be calculated from the Henry s law constant or from the vapor pressure of the pure substance and the limiting activity coefficient. Thus, if the deviation of the solution from Raoult s law behavior is known, calculation of the standard state free energy of solvation requires only the vapor pressure of the pure substance (in the standard state... 

Another way to obtain HENRY S constant H of undissociated acid is from high concentration vapor-liquid equilibria where dissociation is negligible. Using NRTL equation for the representation of the data of BROWN and EWALD (6) at high concentration in acetic acid (10 2 < x < 1), he finds the limiting activity coefficient of undissociated acid at 100°C... 

Bendova, M., Rehak, K.. Matous, J., and Novak, J.P. Liquid + liquid equilibrium in the ternary systems water + ethanol + dialkyl phthalate (dimethyl, diethyl, and dibutyl phthalate) at 298.15 K, /. Chem. Eng. Data, 46(6) 1605-1609, 2001. Benes M. andDohnal, V. Limiting activity coefficients ofsome aromatic and aliphatic nitrocompounds in water, / Chem. Eng. Data, 44(5) 1097-1102, 1999. 

Hovorka, S., Dohnal, V., Roux, A.H., andRoux-Desgranges, G. Determination of temperature dependence of limiting activity coefficients for a group of moderately hydrophobic organic solutes in water. Fluid Phase Equilib., 201(1) 135-164, 2002. 

From an environmental point of view, it is often of most interest to know the activity coefficient of an organic compound in dilute aqueous solution. This activity coefficient is commonly denoted as yZ, and is referred to as limiting activity coefficient or infinite dilution activity coefficient. 

Benes M., Dohnal, V. (1999) Limiting activity coefficients of some aromatic and aliphatic nitro compounds in water. J. Chem. Eng. Data 44, 1097-1102. 

Thomas, E.R., Eckert, C.A. Prediction of limiting activity coefficients by a modified separation of cohesive energy density model and UNIFAC. End. Eng. Chem. Process Des. Dev., 1984,23 194-209. 

Smiley191 has measured gas-liquid retention volumes to obtain values for the activity coefficients at infinite dilution for eight different five-carbon hydrocarbons in NMA. The activity coefficients were determined at 40, 70, and 100 °C and, from the temperature dependence, values for the partial molar heats of solution were calculated. Frost and Bittrich192) have reported limiting activity coefficients of benzene and cyclohexane in NMA at 25 and 50 °C. 

Li, J., Carr, P.W. (1993) Measurement of water-hexadecane partition coefficients by headspace gas chromatography and calculation of limiting activity coefficients in water. Anal Chem. 65, 1443-1450. 

C, calculated-limiting activity coefficient data, Dohnal Fenclova 1995)... 

Thomas, E.R, and Eckert, C.A. (1984). Prediction of Limiting Activity Coefficients by a Modified Separation of Cohesive Energy Density Model and UNIFAC. I EC.Process Des.Dev., 23, 194-209. 

BERGMANN ECKERT Limiting Activity Coefficients of Nonelectrolytes 219... 

The activity coefficient of a component in a mixture is a function of the temperature and the concentration of that component in the mixture. When the concentration of the component proaches zero, its activity coefficient approaches the limiting activity coefficient of th component in the mixture, or the activity coefficient at infinite dilution, y . The limiting activity coefficient is useful for several reasons. It is a strictly dilute solution property and can be used dir tly in nation 1 to determine the equilibrium compositions of dilute mixtures. Thus, there is no reason to extrapolate uilibrium data at mid-range concentrations to infinite dilution, a process which may introduce enormous errors. Limiting activity coefficients can also be used to obtain parameters for excess Gibbs energy expressions and thus be used to predict phase behavior over the entire composition range. This technique has been shown to be quite accurate in prediction of vapor-liquid equilibrium of both binary and multicomponent mixtures (5). 

The limiting activity coefficient is also of great theoretical interest At infinite dilution each solute molecule is surrounded by only solvent mol ules, and the most nonideal conditions are represented, yi is in fact an excess property, so like-pair interactions are normalized out. Since only unlike-pair interactions are involved, any composition dependence of the solute on the properties of the mixture are removed. 

Direct measurement of y would confirm whether or not the solution is infinitely dilute at saturation. Lobien and Prausnitz (23) have attempted to measure this effect in a few systems by comparing the solubility limit with measurements of y from differential ebulliometry. The systems they studied all had solubilities of a few percent, and for these systems they found significant deviations from yi = 1/xi. It would be useful to have measurements for more dilute solubilities, but in this case the limiting activity coefficient becomes very large, and ebulliometry is inapplicable for high relative volatilities. Perhaps such data could be taken by ebulliometry for systems where the solute is much less volatile than water, or by chromatographic methods. 

Limiting activity coefficient data fcr a few water solvent systems measured by various researches using the techniques discussed are shown in Table II. The y ... 

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