Psg°i s the vapor pressure of pure mercury at the temperature, T, under study. Png is the mercury vapor pressure at the temperature, T, under study. The variations of the activity coefficient with the temperature are within the range of the precision of the measurements: ~1_2%)X "Hg / The values of 7Hg are indicated in Table II. For the solid liquid phase, we used the liquidus curve given by Ito et al. ( 5). The activity coefficient of mercury in the presence of indium can be considered as independent of the temperature in the range of temperature studied. On the other hand, the dependence as regards the concentration of indium is important and the mercury-indium amalgams deviate negatively from ideality.

Isobarlc vapor-liquid equilibrium data lor the systems ethyfbenzene-dlmethylformamlde and p-xytene-dimethylformamlde were obtained at 760 mmHg pressure by using a vapor recirculating type of equilibrium still. Both the systems form minimum-boiling azeotropes. The activity coefficient data were tested for thermodynamic consistency by the methods of Herrington, Black, and Norrlsh and Twlgg and correlated by the van Laar, Wilson, and Redllch-Kleter equations.

The infinite-line-charge theory (20) gives the dependence of 0V on In c at extreme (but not infinite) dilution (d0v/d In c) = (azp Vm/2zcX)(d In c/d In P) =

Experimental vapor-liquid equilibrium data have been obtained for the system propionic acid-m-xylene at 760 mmHg pressure using a recirculating type equilibrium still. The system formed a minimumboiling azeotrope. The activity coefficients were calculated from experimental data taking into consideration vapor phase imperfection. NothnageFs correlation based on chemical theory of vapor imperfection was used to estimate second virial coefficients. The data have been tested for thermodynamic consistency and correlated by Wilson equation as modified by Katayama and Tsuboka.

Vapor-liquid equilibria for the systems, propionic acidisopropylbenzene and propionic acid-o-xylene, were obtained at 760 mmHg using a vapor recirculatory type of still. The activity coefficients were obtained by taking into consideration vapor phase association. Nothnagel's correlation based on chemical theory of vapor imperfections was used. The data satisfied the Herington criterion of thermodynamic consistency and were correlated by the Wilson equation.