Temperature‐concentration oscillations of crystal‐solution phase equilibria in the presence of trace impurities of surface‐active agents

Abstract

AbstractUsing the examples of aqueous salt solutions NaNO3, KNO3, RbNO3, K2SO4, NaBr·2H2O, KBr, and NH4NO3, it was experimentally proven that the new phenomena, i.e. temperature‐concentration oscillations of crystal‐solution phase equilibria detected previously in the range of 15–45 °C remain in the presence of trace impurities (10‐4–10‐3 wt. %) of ion‐active organic matters. The signs of breaks transformation into pair oscillations of “maximum‐minimum” type are established for the K2SO4, NaBr, KBr solutions. The efficiency of influence of trace impurities on phase equilibria sharply rises in the areas of the temperature‐concentration oscillations (the saturation temperature ranges up to 10 K). The impurity efficiency is promoted by the presence of the amides in its content (as compared with the sulphates) and an increase in length of the hydrocarbon radical. The phenomenon is absent in case of an addition of ion‐inactive compounds. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)