Phase rule investigations of the three component systems phenol-water-salt at 25 degrees centigrade

by N. A. Brown

Institution: University of Canterbury
Department: Chemistry
Year: 1937
Record ID: 1316084
Full text PDF: http://hdl.handle.net/10092/7779


The phenol – water systems and the effect of the addition of a third component on the mutual solubilities have been the subject of much investigation during the last twenty or thirty years. The aspect usually considered has been the so-called “salting out” effect of an added salt on the phenol water solutions. The method of investigation for the most part has been the quantitative effect of the added salt on the critical solution temperature. This method has been criticised by Bailey, (J.C.S. 123, 2579, 1923). He states that it is no more satisfactory for two liquid layers than it would be if applied to the saturation curve of the three component system; a number of isolated points are obtained which lie on the surface separating the region of heterogeneity from the rest of the figure, and the comparison of results is difficult. He maintains that the most satisfactory treatment of such systems is a complete phase rule study. Bancroft (J. Phys. Chem. 1897 I) showed that the phenomena observed in such systems could be theoretically predicted from considerations of the phase rule. If a given system is represented by the usual triangular method, for any given temperature one has normally a saturation curve, and a binodal curve, and the many complications which may arise are due to a combination of the two. It is obvious that if the theoretical aspect of the various cases of salt addition to phenol water systems is to be studies, the phase rule method is most satisfactory. It shows clearly the general effect on the critical solution temperature; it indicated any formation of compounds; and the general form of the curve in the case of “salting-in” shows whether this is due to solubility of the substances in both liquids or to abnormal behaviour such as the formation of complexes in solution. Finally, by comparing the actual curves obtained for the different systems studied the various possibilities can be clearly distinguished without reference to numerical figures.