Selected X-ray diffraction and differential scanning calorimetry investigations of the binary system K-palmitate/glycerol

Three mole fractions of the binary system K-palmitate/glycerol (KC16/Gl) x( KC16) = 0.30, 0.37 and 0.50 have been investigated as a function of tempera ture by small- and wide-angle X-ray diffraction investigations and differen tial scanning calorimetry (DSC) measurements. The existence of a gel-like r egion. named G(1) in the preliminary binary phase diagram [4], could not be confirmed. Consequently, a corrected version of the phase diagram of the K C16/Gl system is established. According to this corrected phase diagram at low K-palmitate concentrations, x(KC16) < 0.25, the transitions crystalline phase (C) <----> hexsagonal phase, chains fluid (H-alpha) <----> isotropic , micellar phase (S) occur with rising temperature. At x(KC16) > 0.25 the t ransitions C <----> gel phase (G) <----> lamellar phase, chains fluid (L-al pha) were observed. X-ray diffraction and DSC measurements provided concord ant results. Only differences in the phase transition temperatures from DSC curves obtained at rising and falling temperatures were observed. The phas e transitions C <----> G, G <----> L-alpha and G <----> H-alpha correlate w ith a sharp shift in the d value of the first small-angle reflection. The o ccurrence of the G phase is accompanied by a distinct split of the first sm all-angle reflections. Simultaneously, the wide-angle reflections change an d the peak intensity is reduced.