DISPERSION MORPHOLOGY DIAGRAMS FOR 3-PHASE, MICROEMULSION EMULSIONS .2. DISAPPEARANCE OF MORPHOLOGY-TRANSITION LINES

The limits over which the oil-rich top phase (T) middle-phase microemu lsion (M), or water-rich bottom phase (B) is the continuous phase in s teady-state, three-phase macroemulsions have been determined by means of electrical conductivity measurements for the amphiphile/oil/''water '' system C6H13(OC2H4)(2)OH/n-tetradecane/aqueous 10 mM NaCl. Measurem ents were made at three different temperatures and apparent wettabilit y conditions: (a) 45 degrees C, wetting middle phase; (b) 25 degrees C , no wetting phase; and (c) 12 degrees C, wetting bottom phase. The re sults at 25 degrees C were in accord with expectations from previous p redictions and experiments; but for both two-phase and three-phase :em ulsions no abrupt, ''first-order'' transitions between M- and T-contin uous emulsions at 45 degrees C or between M- and B-continous emulsions at 12 degrees C were found. Instead, these changes of continuous phas e appeared to occur smoothly and continuously between their respective single-phase and two-phase limits. It is not yet clear if the ''disap pearance'' of first-order morphology transitions correlates with phase wettability transitions; the phenomenon suggests the possibility of b icontinuous two-phase and three-phase macroemulsions.