Activity coefficients, at infinite dilution

If the mutual solubilities of the solvents A and B are small, and the systems are dilute in C, the ratio ni can be estimated from the activity coefficients at infinite dilution. The infinite dilution activity coefficients of many organic systems have been correlated in terms of stmctural contributions (24), a method recommended by others (5). In the more general case of nondilute systems where there is significant mutual solubiUty between the two solvents, regular solution theory must be appHed. Several methods of correlation and prediction have been reviewed (23). The universal quasichemical (UNIQUAC) equation has been recommended (25), which uses binary parameters to predict multicomponent equihbria (see Eengineering, chemical DATA correlation). 

Hquid-phase activity coefficient (eq. 6) terminal activity coefficient, at infinite dilution constant in Wilson activity coefficient model (eq. 13)... 

J. Gmehling, J. Menke, M. Schiller, Activity Coefficients at Infinite Dilution DECHEMA, Frankfurt, 1994. 

It can be immediately seen that for components exhibiting Raoultian behaviour, the activity coefficient is equal to unity. The Henry s law constant k is nothing but the activity coefficient Yj. Noting that Henrian behaviour is exhibited when the component i is present in very low concentrations, the constant is also expressed in this case as y and is known as the activity coefficient at infinite dilution. Henry s law may now be stated as... 

The constants in any of the activity coefficient equations can be readily calculated from experimental values of the activity coefficients at infinite dilution. For the Wilson equation ... 

Relatively simple experimental techniques, using ebulliometry and chromatography, are available for the determination of the activity coefficients at infinite dilution. The methods used are described by Null (1970) and Conder and Young (1979). 

Pieratti et ol. (1955) have developed correlations for the prediction of the activity coefficients at infinite dilution for systems containing water, hydrocarbons and some other organic compounds. Their method, and the data needed for predictions, is described by Treybal (1963) and Reid et al. (1987). 

Gruber, D., Langenheim, D., Gmehling, J. (1997) Measurement of activity coefficients at infinite dilution using gas-liquid chromatography. 6. Results for systems exhibiting gas-liquid interface adsorption with 1-octanol. J. Chem. Eng. Data 42, 882-885. 

The finite value of the slope when xB —>0, yB, is the activity coefficient at infinite dilution defined earlier. In terms of activity coefficients eq. (3.46) becomes... 

A graphical integration of the Gibbs-Duhem equation is not necessary if an analytical expression for the partial properties of mixing is known. Let us assume that we have a dilute solution that can be described using the activity coefficient at infinite dilution and the self-interaction coefficients introduced in eq. (3.64). 

Activity coefficients at infinite dilution are in general very important and frequently used in thermodynamic analyses. Examples are analyses of trace element... 

Straver, E.J.M. and de Loos, T. Determination of Henry s law constants and activity coefficients at infinite dilution of flavor compounds in water at 298 K with a gas-chromatographic method, / Chem. Eng. Data, 50(4) 1171-1176, 2005. 

For very hydrophobic compounds, when is very high (10 ), fhere is evidence from field studies involving fish, birds, and animals fhaf fhere is a bioaccumulation or bioconcentration up to food chain [114]. The pesticide DDT is an example of bioaccumulating chemical with a Kqw of —10 . The thermodynamic model for air/water and 1-ocfanol/wafer acfivify coefficients and the importance of the activity coefficient at infinite dilution measurements have been presented as well [114]. 

Activity coefficients at infinite dilution, of organic solutes in ILs have been reported in the literature during the last years very often [1,2,12,45,64, 65,106,123,144,174-189]. In most cases, a special technique based on the gas chromatographic determination of the solute retention time in a packed column filled with the IL as a stationary phase has been used [45,123,174-176,179,181-187]. An alternative method is the "dilutor technique" [64,65,106, 178,180]. A lot of y 3 (where 1 refers to the solute, i.e., the organic solvent, and 3 to the solvent, i.e., the IL) provide a useful tool for solvent selection in extractive distillation or solvent extraction processes. It is sufficient to know the separation factor of the components to be separated at infinite dilution to determine the applicability of a compound (a new IL) as a selective solvent. 

In many publications, the activity coefficients at infinite dilution / j have been determined for alkanes, alk-l-enes, alk-l-ynes, cycloalkanes, aromatic hydrocarbons, carbon tetrachloride, and methanol in the IL at different temperatures. Figure 1.15 presents a plot of the activity coefficients, xrs against chain length, n of hydrocarbons n-alkanes, alk-l-enes, alk-l-ynes, and cycloalkanes for [C6CiIm][Tf2N] [183]. 

Heintz, A., Kulikov, D.V., and Verevkin, S.R, Thermodynamic properties of mixtures containing ionic liquids. 1. Activity coefficients at infinite dilution of alkanes, alkenes, and alkylbenzenes in 4-methyl-M-butylpyridinium tetrafluo-roborate using gas-liquid chromatography, /. Chem. Eng. Data, 46,1526,2001. 

Krummen, M., Wasserscheid, R, and Gmehling, J., Measurements of activity coefficients at infinite dilution in ionic liquids using the dilutor technique, /. Chem. Eng. Data, 47, 1411, 2002. 

Letcher, T.M. et al.. Activity coefficients at infinite dilution measurements for organic solutes in the ionic liquid l-butyl-3-methylimidazolium 2-(2-methoxyethoxy)ethyl sulfate using glc at T = (298.15, 303.15 and 308.15) K, /. Chem. Thermodyn., 37, 587, 2005. 

Letcher, T.M. and Reddy, R, Determination of activity coefficients at infinite dilution of organic solutes in the ionic liquid, trihexyl(tetradecyl)-phospho-nium tris(pentafluoroethyl)trifluorophosphate by gas-liquid chromatography. Fluid Phase Equilib., 235,11, 2005. 

Balyes, J.W., Letcher, T.M., and Moolan, W.C., The determination of activity coefficients at infinite dilution using GLC with moderately volatile solvents,... 

To determine the activity coefficient at infinite dilution, packed colunms were prepared containing the IL-coated chromosorb support [12-14]. The examined mixture of probe molecules was then injected under infinite dilution conditions. The value of y can be calculated from Equation 4.4, as defined by Cruickshank and coworkers [15] ... 

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