Light Scattering and Pseudospinodal Curves: The Isobutyric-Acid-Water System in the Critical Region

1969 ◽  
Vol 185 (1) ◽  
pp. 219-226 ◽  
Author(s):  
B. Chu ◽  
F. J. Schoenes ◽  
Michael E. Fisher
Keyword(s):  
Light Scattering ◽  
Critical Region ◽  
Water System ◽  
Isobutyric Acid ◽  
Acid Water

Excess partial molar enthalpies in the water-rich region of the isobutyric acid – water system

1991 ◽  
Vol 69 (7) ◽  
pp. 1065-1069 ◽  
Author(s):  
William W. Y. Siu ◽  
Terrance Y. H. Wong ◽  
Lisa C. F. Chao ◽  
Yoshikata Koga
Keyword(s):  
Phase Separation ◽  
Water System ◽  
Isobutyric Acid ◽  
Acid Water ◽  
Rich Region ◽  
Two Phase ◽  
Fourth Derivative ◽  
Mixing Schemes ◽  
Partial Molar Enthalpies ◽  
Structure Enhancement

The excess partial molar enthalpies of isobutyric acid (IBA), HmE(IBA), and those of H2O, HmE(H2O), were measured in aqueous solutions of IBA. The temperature dependence of HmE(IBA) at the infinite dilution suggested that the structure enhancement of the solvent H2O by IBA is weaker than those by tert-butanol (TBA) or 2-butoxyethanol (BE). The concentration dependence of HmE(IBA), and that of the enthalpic IBA–IBA interaction, N{∂HmE(IBA)/∂nB}, shows that there are two distinct mixing schemes bounded at about xB = 0.03, before reaching the two phase separation. Namely, the IBA–IBA interaction is repulsive below this boundary, while above this boundary it becomes attractive leading eventually to phase separation at a higher concentration. The transition between the two schemes is associated with a peak(negative) anomally in the fourth derivative of the free energy, N2 {∂2HmE(IBA)/∂nB2}.Key words: excess partial molar enthalpies, isobutyric acid – water, transition in mixing scheme.

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