Volumetric properties of the decylammonium chloride and cesium perfluorooctanoate from density measurements

Measurements of density of aqueous solutions of decylammonium chloride (DAC l) and cesium perfluorooctanoate (CsPFO) in the range of concentration from 0 to 50% by weight were carried out at 20, 30 and 40 degrees C. From these results the apparent molal volume of aqueous solutions of DACl and CsPFO h ave been determined as a function of concentration and temperature. On the basis of the apparent molal volume at concentration higher than the critica l micelle concentration (CMC), the apparent molal volume at the CMC and the volume change upon micellization (Delta V) have been determined. The Delta V has also been evaluated from the calculation of the partial molal volume s above and below the CMC. There is a good agreement between the average va lues of Delta V for DACl and CsPFO at a given temperature determined in bot h methods. However, Delta V for CsPFO depends on concentration, particularl y in the region of the highest concentration. It was stated that Delta V fo r DACl and CsPFO depends only slightly on the temperature and that Delta V for CsPFO is higher than for DACl. It was also found that the volume of DAC l and CsPFO molecules at the CMC is only barely higher than their volumes i n solid state, and at concentrations higher than the CMC their volume is cl ose to that calculated in an hypothetical liquid state. (C) 1999 Elsevier S cience B.V. All rights reserved.