Thermochemical investigations of associated solutions: calculation of solute--solvent equilibrium constants from solubility measurements.
A simple solution model that has lead to successful predictive equations for the partial molar excess properties of a solute in simple binary solvent mixtures containing only nonspecific interactions is extended to include association between the solute and one of the solvent components. An expression is derived and tested for its ability to describe anthracene solubilities in binary solvent mixtures containing benzene. The best description of the experimental solubilities requires the formation of a 1:1 anthracene-benzene complex, with a molarity-based equilibrium constant of KcAC approximately equal to 0.107 M-1. In comparison, a stoichiometric complexation model which attributes all solubility enhancement to the formation of anthracene-benzene complexes requires a somewhat larger equilibrium constant (KcAC approximately equal to 0.228 M-1) to describe the solubility behavior of anthracene in the benzene-n-heptane system. The results of these calculations illustrate that the determination of solute-solvent equilibrium constants from solubility data depends on the theoretical model used and the manner in which nonspecific interactions are incorporated into the model.
Solubility of polar organic solutes in nonaqueous systems: role of specific interactions.
The changes in solubility of several polar organic solutes when polar organic solvents are added to a relatively inert solvent such as isooctane were determined. The relative changes in solubility predicted from regular solution theory using solubility parameters often did not agree with the observed results. However, the solubilities could be rationalized mathematically by assuming the formation of specific solute-solvent complexes. Agreement of the thermodynamic data reported here with such models provides further evidence that specific interactions, when they occur, are more important than the bulk properties of the pure components in determining drug solubilities in nonaqueous systems. Specific examples demonstrate the relationship between the solubility and molecular structure of the solute and solvent. For example, solubility can be related to the hydrogen-donating and hydrogen-accepting abilities of the solute and solvent. Steric factors also appear to play a role in solubility, while structural modifications in a solute or solvent molecule far removed from the interactive functional group have little influence on molar solubility changes with the added polar cosolvent.
The effect of family size on parents' labor supply and occupational prestige: Evidence from Taiwan and Mainland China
Abstract This paper studies the effect of family size on parents' labor supply and occupational prestige, using the censuses of both Taiwan and Mainland China. We rely on the exogenous increase in child quantity that results from having twins at the first birth. Our results indicate that an increase in family size has negative effects on the labor supply of mothers, but not of fathers, in both Taiwan and Mainland China. In addition, we find that in Taiwan fathers tend to switch to occupations with lower prestige scores in response to an increase in family size. However, the negative effect of family size on occupational prestige is not observed in Mainland China, where the occupational mobility is low.