Fish-cuts, phase prisms

Figure 3.3 Two types of bidimensional cuts through multidimensional phase prisms, (a) Cut through a phase prism at a 1 1 water-to-oil ratio as a function of the temperature (7) and the surfactant concentration (y), the so-called fish diagram, (b) Cut through a phase prism at constant 7 and y as a function of the ethoxylation degree EON) and the water-to-oil ratio (WOR), the so-called x diagram. ...

The easiest way to represent the changes in the phase behavior of these systems is to monitor the changes in a so-called fish diagram. This specific cut through the phase prism is schematically shown in Fig. 12. 

Eigure 3a shows a section through the phase prism as a function of temperature and surfactant concentration. The ratio of the volume fractions of water and oil is fixed. Because of its characteristic fishlike shape, this section is called a fish cut [57]. The phase diagram is to a good approximation mirror symmetrical with respect to the phase inversion temperature T, where the value for T depends only on the choice of components and takes the value T = 305.6 K for... 

To determine complete ternary phase diagrams, in particular at a number of different temperatures, is a lengthy process, and has been carried out for only for a few systems. Rather, one often reduce the number of composition degrees of freedom by one and studies a planar section through the phase prism. The section defined by 0vv = 0o ( fish-cut ) is shown schematically in Figure 17.3. In this section, one can determine 7] and Tu and the minimum amount of surfactant necessary to solubilize equal amounts of water and oil, which we here denote as 0. The lower 0, then the more efficient is the surfactant. We see also that the microemulsion at higher surfactant concentrations is in equilibrium with a lamellar phase (L ), a typical feature of long-chain surfactants. 

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