Activity coefficient of nonelectrolytes

Li, J., Dallas, A.J., Eikens, D.I., Carr, P.W., Bergmann, D.L., Hait, M.J., Eckert, C.A. (1993) Measurement of large infinite dilution activity coefficients of nonelectrolytes in water by inert gas stripping and gas chromatography. Anal. Chem. 65, 3212-3218. 

Long, F.A. McDevit, W.F. "Activity Coefficients of Nonelectrolyte Solutes in Aqueous Salt Solutions," Chem. Rev.,... 

Roughly half of the data on the activities of electrolytes in aqueous solutions and most of the data for nonelectrolytes, have been obtained by isopiestic technique. It has two main disadvantages. A great deal of skill and time is needed to obtain reliable data in this way. It is impractical to measure vapor pressures of solutions much below one molal by the isopiestic technique because of the length of time required to reach equilibrium. This is generally sufficient to permit the calculation of activity coefficients of nonelectrolytes, but the calculation for electrolytes requires data at lower concentrations, which must be obtained by other means. 

F.A. Long and W.F. McDevit, Activity coefficients of nonelectrolyte solutes in aqueous salt solutions, Chem. Rev. 51... 

BERGMANN ECKERT Limiting Activity Coefficients of Nonelectrolytes 219... 

Another complication which enters in more concentrated solutions is the salting-out effect (cf. p. 68). The activity coefficients of nonelectrolytes also depend upon the ionic strength of the solution ... 

Nonelectrolytes—dissolved gases, organic molecules, neutral ion pairs, and undissociated weak acids and bases—are also nonideal soiutes in water and are-common constituents of soil solutions. Their activities also vary nonlinearly with concentration, particularly at high concentrations. The activity coefficients of nonelectrolytes at low concentrations are approximated by... 

The activity coefficients of nonelectrolytes (uncharged molecules) can generally be considered equal to unity in ionic strengths up to 0.1, and deviations from this approximation are only moderate in ionic strengths as high as 1. Undissociated acids, HA, are honelectrolytes whose activity coefficients can be taken as unity. 

Note that the first of these is essentially the same as the equation derived in 12.4.5 (I = ln(l + 0.0180153m)) for the conversion of Henryan activity coefficients of nonelectrolytes from the molality scale to the mole fraction scale, the only difference being the introduction of u. 

The theory for predicting the activity coefficients of nonelectrolytes in aqueous solution is not as well developed as for electrolytes. An empirical equation of the form... 

Long, F. A. and McDevit, W. F., 1952, Activity coefficients of nonelectrolytes in aqueous electrolyte solutions. Chem. Rev., 51 119-69. 

In 1952, F.A. Long and W.F. McDevit (S15) presented the results of their extensive study of the activity coefficients of nonelectrolytes in aqueous salt solutions. Their results for the molar activity coefficients of undissociated nonelectrolytes in salt solutions were based mainly on solubUity, distribution and vapor pressure measurements. They noted that since the activity coefficient for any species i could be expressed as a power series to show the effects the concentrations of all solutes j in the solution ... 

This section describes several methods by which activity coefficients of nonelectrolyte substances may be evaluated. Section 9.6.3 describes an osmotic coefficient method that is also suitable for electrolyte solutes, as will be explained in Sec. 10.6. 

Group interaction models have achieved remarkable success in the description of activity coefficients of nonelectrolyte solutions. Notable in this development are the pioneering work by Pierotti, Deal and Derr (] ), Wilson and Deal ( ), and subsequent contributions by Scheller ( 3), Ratcliff and Chao W, Derr and Deal ( 5), and Fredenslund, Jones, and Prausnitz ( ). 

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