par Huet, Joëlle 
;Philippe, Roger ;Bono, D.
Référence Bulletin des Sociétés chimiques belges, 62, 7-8, page (436-447)
Publication Publié, 1953
;Philippe, Roger ;Bono, D.Référence Bulletin des Sociétés chimiques belges, 62, 7-8, page (436-447)
Publication Publié, 1953
Article révisé par les pairs
| Résumé : | Considering an associated binary solution, e. g. alcohol + carbon tetrachloride, as a system of single molecules („monomers”) and associated complexes in equilibrium with one another, it has been shown in the first paper of this serie, by using the principle of detailed balancing of elementary processes, that the relation fA /fB = α (1.) holds between the activity coefficients if the deviations from the laws of perfect solutions can be entirely ascribed to the presence of the complexes. α denotes the fraction of molecules of the associated constituent which appear as single molecules. Equation (1.) implies that unassociated molecules A („monomers”) and molecules of solvent B play equivalent roles in the solution. This relation, which is completely independent of any hypothesis about the mode of association, can be checked by comparing thermodynamic measurements of fA and fB with values of α obtained from the spectroscopic study of the intensity of the OH vibration band. In the preceding paper, relation (1.) has been verified for a certain number of associated solutions. Yet small deviations have been observed. In order to understand the origin of these residual deviations we have studied the thermodynamic and spectroscopic properties of the systems ethyl alcohol‐carbon disulphide and ethyl alcohol‐dioxan. In both systems we expected important deviations from formula (1). The first system presents an upper critical mixing temperature at −23° 5 C. In the second case there is a strong interaction between the oxygen atoms of dioxan and the hydroxyl group of ethyl alcohol. The interaction between a monomer of alcohol and dioxan is certainly much stronger than the interaction between two molecules of dioxan either the non polar interaction of two monomers (the polar interaction is taken account separately by the presence of complexes). The experimental results have entirely confirmed this point of view. The difference between α and the ratio fA/fB may be expressed by a residual excess free energy which is found to be positive in the system ethylalcohol‐carbon disulphide and negative in the system ethyl alcohol‐dioxan. The order of magnitude of this residual excess free energy is discussed. Copyright © 1953 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim |
