Liquid crystal boundary definition

The polyphasic region contains a three-phase zone surrounded by three two-phases zones. Systems whose composition lies in the three-phase zone separate into an amphi-phUe-rich phase (m), which is in the middle of the diagram at the boundary of the single-phase region, and two excess phases, which are essentially pmre aqueous phase and pure oil. This amphiphile-rich phase, which is found to obey, in most cases, the definition proposed for a bicontinuous microemulsion or a liquid crystal, has been called a middle phase because its intermediate density makes it appear in between the oil and water phases in a test tube. Because the middle phase is at equilibrium with both excess phases, it cannot be diluted either by water or oil, and it is thus neither water nor oil-continuous. This is another hint of the bicontinuous nature of this phase, as conductivity and viscosity measurements and other experimental evidences have shown [20-22,37-40]. 

Pure, simple substances separate from solution on cooling as crystals. These crystals have a sharp melting point, which marks precisely the boundary between the liquid and solid states. They also have a definite and consistent shape. This shape is due to the pattern in which the atoms, ions or molecules are arranged. Thus crystals of common salt are always cubic. The arrangement of the Na+ and Cl ions is in a cubic pattern (Fig. 8), which extends in all directions to fill and form the shape of a single crystal. 

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