A phase-rule study of multiple-phase formation in a model emulsion system containing water, n-octanol, n-dodecane and/a non-ionic surface-active agent at 10 and 25°

Abstract

A four‐component emulsion system containing the non‐ionic surfactant C8H17 (O·CH2·CH2)6OH has been investigated, particularly in regions in which liquid crystal or more than two condensed phases are formed. Liquid crystal does not exist in the binary surfactant‐water system at 25° but extensive regions form when the organic liquids octanol and dodecane are present, although these are not joined to the main two‐liquid regions of the emulsion system. The surfactant is almost completely dissolved in the aqueous phase in water‐dodecane mixtures but when substantial amounts of octanol are also present the partition coefficient is reversed in favour of the organic phase. At certain intermediate compositions three liquid phases are present. The significance of these results to the system as an emulsion are briefly discussed.

Effect of micelle formation and the nature of the oil-phase on the distribution of a non-ionic surfactant in three- and four-component emulsions

“…Furthermore, practical difficulties made it impossible to maintain exactly the same ratios of water, octanol and dodecane, which may have led to some variation in the composition of the phases and therefore to the partition of surfactant. Another possibility is that the triangular plane selected (see variation in ratios recorded in the experimental section) may have infringed the boundaries of the three-liquid region (Marland & Mulley, 1971) with which it closely borders. (During equilibration several mixtures appeared to consist initially of three phases before eventually changing to form two phases.…”

“…The assumption that all the tie lines in this region lie in triangular planes having the water-C8E6 axis of the model tetrahedron used to represent the system (Marland & Mulley, 1971) as a common side, is only approximately true (Marland, 1970). Furthermore, practical difficulties made it impossible to maintain exactly the same ratios of water, octanol and dodecane, which may have led to some variation in the composition of the phases and therefore to the partition of surfactant.…”

“…The preparation and purity of the components have been described previously (Marland & Mulley, 1971). …”

“…Previously Marland & Mulley (1971) noted that the surfactant (3,6,9,12,15,18-hexaoxahexacosan-1-01 ; C,,H,, [O-CH,.CH,],OH) was dissolved mainly in the water in water-dodecane mixtures but in the 'oily' phase when octanol was substituted for dodecane. The plait points in both cases were very close to one apex of the triangles used to represent the systems in that phase-rule study.…”

Pharmaceutical Sciences—1971: Literature Review of Pharmaceutics

“…The liquid crystalline phase did not exist in the binary surfactant-water system but was formed only in the presence of the organic liquids. The results were discussed with respect to their significance in the emulsion systems (963). The presence of a liquid crystalline layer at the interface of a stable emulsion was verified, and its role in the emulsion stabilization was discussed (964).…”