Chemical Equilibrium and Critical Phenomena: Solubility of Indium Oxide in Isobutyric Acid + Water Near the Consolute Point

Abstract

We have determined the solubility, s, of indium oxide in the liquid mixture isobutyric acid + water along the critical isopleth at temperatures above the upper critical solution temperature near 299 K. When plotted in van’t Hoff form with ln s vs 1/T, the measurements of solubility lie on a straight line for values of the absolute temperature, T, which are sufficiently in excess of the critical solution temperature, T c. The sign of the slope, (∂ ln s/∂(1/T)), indicates that the enthalpy of dissolution is endothermic. When the temperature is within 1 K of T c, however, the slope departs from its constant value and appears to diverge toward negative infinity. The principle of critical point universality predicts that a divergence in (∂ ln s/∂(1/T)) is to be expected for T near T c in those cases where the stoichiometry of the dissolution reaction involves both components of the solvent; moreover, the Gibbs−Helmholtz equation predicts that if the enthalpy of solution is endothermic, the sign of the divergence should be negative. Both of these predictions are confirmed by the experimental data.

Phase Rule and the Universality of Critical Phenomena in Chemically Reacting Liquid Mixtures

“…The dissolution of metal oxides by acid/base reaction in IBA/H 2 O produces mixtures having at least six chemical components. We will show that F = 3 in every case where a solubility critical effect has been reported. ,− Nonetheless, we should not neglect the fact that solubility critical effect can be anticipated even in the absence of reaction, as has recently been demonstrated in the case of the dissolution of excess phenolphthalein in a mixture of nitrobenzene + dodecane . This system consists of three components, and the phase rule calculation shows F = 3 …”

Chemical Equilibrium and Critical Phenomena: The Solubilities of Iron(III) Oxide and Cobalt(II,III) Oxide in Isobutyric Acid + Water Near the Consolute Point

“…The solvent power of these liquids permits them to be used to study the effect of the critical point on the net rate of reaction [23][24][25][26][27][28][29][30][31][32][33] and also on the position of chemical equilibrium [11,34,35].…”

“…Like Fe 2 O 3 and Co 3 O 4 , MnO 2 [11] and In 2 O 3 [35] both dissolve endothermically in isobutyric acid + water, and the van't Hoff slope, (∂ ln s/∂(1/T )) P, G=0 , is observed to tend toward negative infinity as T approaches T c . In contrast to these three, Al 2 O 3 [11] dissolves exothermically, and the van't Hoff slope tends toward positive infinity in the critical region.…”

Kinetics of two redox reactions in 2‐butoxyethanol and water near its critical point of solution

“…The dynamic property, such as mutual diffusion coefficient, exhibits vanishing as the temperature approaches to critical temperature . The chemical reaction rate exhibits interesting critical behaviors in the liquid–liquid critical binary solutions resulting from critical fluctuation …”

“…Snyder and Eckert measured the rate of the Dieles–Alder reaction of isoprene with maleic anhydride in critical binary solutions (binhexane/nitrobenzene, hexane/nitroethane) and found that the reactions accelerated 30–40% near the critical point. Baird et al . investigated the rates of various reactions in different critical binary solutions.…”