Middle soap

Middle soap phase, 22 726 Middlings, 16 603 Mid-ir lasers, 22 180 Mid-ir region, 14 234-236 MIDREX process, 14 513, 514 Midwest Research Institute, on PVC waste incineration, 25 681... 

A mesomorphic (liquid-crystal) phase of soap micelles, oriented in a hexagonal array of cylinders. Middle soap contains a similar or lower proportion of soap (e.g., 50%) as opposed to water. Middle soap is in contrast to neat soap, which contains more soap than water and is also a mesomorphic phase, but has a lamellar structure rather than a hexagonal array of cylinders. Also termed clotted soap . See Neat Soap. 

Isotropic solution (nigre lye). With these it must be noted that these solutions can be transformed into gels by addition of electrolytes, after which a separation into two layers can follow — the region of the coacervation of soap solutions studied later by Bungenberg de Jong and his pupils 2°. Middle soap, an anisotropic (polarising microscope) viscous solution which contains still rather a lot of water (about 50%). 

Neither neat soap nor middle soap is miscible with the isotropic solution. 

A Neat Soap B Middle Soap F Nigre J Brine (Lye)... 

K Neat Soap-Middle Soap L Nigre-Brine(Lye)... 

Besides the lamellar liquid crystals just described, others are known to exist. We shall discuss only one here namely, the nematic liquid crystals illustrated by the middle soap phase of a typical soap-water system. An unoriented sample made up of many micro-liquid crystals of this sort will give a series of concentric... 

Water can readily permeate the mass of the already porous product to give a slushy tablet. Hydrophobic or water-repellent substances are required. Soaps do not tend to be porous, and the water penetration is very slow owing to the formulation of the well-known middle soap that has a jell-like structure. 

Ekwall and Baltcheffsky [265] have discussed the formation of cholesterol mesomorphous phases in the presence of protein-surfactant complexes. In some cases when cholesterol is added to these solutions a mesomorphous phase forms, e.g. in serum albumin-sodium dodecyl sulphate systems, but this does not occur in serum albumin-sodium taurocholate solutions [266]. Cholesterol solubility in bile salt solutions is increased by the addition of lecithin [236]. The bile salt micelle is said to be swollen by the lecithin until the micellar structure breaks down and lamellar aggregates form in solution the solution is anisotropic. Bile salt-cholesterol-lecithin systems have been studied in detail by Small and coworkers [267-269]. The system sodium cholate-lecithin-water studied by these workers gives three paracrystalline phases I, II, and III shown in Fig. 4.37. Phase I is equivalent to a neat-soap phase, phase II is isotropic and is probably made up of dodecahedrally shaped lecithin micelles and bile salts. Phase III is of middle soap form. The isotropic micellar solution is represented by phase IV. The addition of cholesterol in increasing quantities reduces the extent of the isotropic... 

Figure 4.37 Phase diagrams of sodium cholate (NaC), water (W), lecithin (L). Systems (a) with no added cholesterol (b) with 0.5 % cholesterol (c) with 2 % cholesterol and (d) with 4% cholesterol. In the system without cholesterol the three paracrystalline phases are labelled I, II, and III. Phase I is analogous to neat soap of aqueous soap systems. Phase II is a cubic phase , and phase III is analogous to the middle soap phase of common soap systems. Phase IV is isotropic micellar system. X in diagram (b) represents the composition of normal human gall-bladder bile. From Small et al. [267, 268].

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