Soap-water systems

Potassium iodide, 20 634 Potassium ions, 20 597, 598, 641 in soap-water system, 22 727 Potassium isotopes, 20 598 Potassium magnesium sulfate, 20 626 Potassium manganate(V), 15 592 Potassium manganate(VI), 15 594-596 Potassium metal, 20 604 production of, 20 600 reducing power of, 20 599 Potassium muds, 9 4 Potassium niobate, 17 152-153 Potassium nitrate, 20 609, 634-636 solubility of, 20 636t uses of, 20 636... 

Soap making, 22 723 as industry, 22 723, 724 raw materials in, 22 732-736 ternary soap-water systems and, 22 727 Soap micelles... 

Soluble electrolytes, ternary soap-water systems and, 22 727 Soluble glass, 22 452 Soluble hydrophilic dyes, 9 190 Soluble microbial products (SMP) in biological wastewater treatment, 25 896. 897... 

A cubic phase in soap-water systems was described in the work by Luzzati and co-workers (1960) in which the lattice was then assumed to be face-centred. Cubic phases were also observed in other lipid systems (cf. Clunie et aL, 1965). A structure consisting of water spheres in a hydrocarbon chain matrix was then proposed by Luzzati and Reiss-Husson (1966). Soon afterwards Luzzati and Spegt (1967) analysed the structure of the cubic phase of strontium myristate which was reported to consist of two networks of rods formed by the polar... 

Wennerstrom (1981) and their calculation of stability regions of the different phases in soap-water systems and in the aerosol OT-water system are in good agreement with the experimental observations. A few additional aspects of structural relationships between phases will be considered here. 

The phase diagram show in Fig. 8.13 is characteristic for a soap-water system. The structures occurring and the phase relations were determined in the classical work by Luzzati et al (1960). Soaps of different chain lengths show an L -phase (termed neat in old soap literature) at low water content and at higher water content there is a large region where the //i-phase (termed middle in earlier literature) exists. Between the Hi and the L -phase Luzzati et al. (1960) described some complex liquid-crystalline phases which with present knowledge on amphiphile-water systems probably can be better... 

The phase described by Lutton (1966) as a middle phase, which is the term used in soap-water systems for the hexagonal phase Hi, is in fact the inverse structure, i.e. phase Hu. Furthermore the phase... 

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... 

The most important aspect of the emulsifier action appears to be its orientation at the interface between the two liquids. A soap consists of a long hydrophobic hydrocarbon chain (tail) and a hydrophilic polar end (head). In a oll-soap-water system, the polar head being strongly attracted to water will orient itself towards water and the non-polar tail will point towards the oil. By obeying the principle of minimal surfaces, the liquid which has a higher surface tension will tend to draw itself into spheres and will be surrounded by the liquid whose surface tension was more markedly lowered (see Figure 7.9). 

Abundance of sodium soap in a oll-soap-water system resulting in a oil-in-water emulsion... 

Abundance of calcium soap in a oil-soap-water system resulting in awater-in-oil emulsion... 

If in an oil-soap-water system, the proportion of calcium soap to sodium soap is varied, the emulsifying action of the combination of soaps will depend upon the ratio of metal ions. Clowes found out a critical ratio of calcium ion to sodium ion experimentally which produced no emulsion. This critical ratio was Ca Na = 1 4. If calcium is preponderant above this ratio, an emulsion with oil as the continuous phase results, while any preponderance of sodium soap 5delds emulsions of oil-in-water t3Tje. 

FIGURE 1.16. Phase diagram for a typical soap-water system. The dashed line shows the minimum concentration for micelle formation. 

Binary Soap-Water System Mixtures of soap in water exhibit a rich variety of phase structures (4, 5). Phase diagrams chart the phase structures, or simply phases, as a function of temperature (on the y-axis) and concentration (on the x-axis). Figure 2.1 shows a typical soap-water binary phase diagram, in this case for sodium pahnitate-water. Sodium palmitate is a fully saturated, 16-carbon chain-length soap. At lower temperatures, soap crystals coexist with a dilute isotropic soap solution. Upon heating, the solubility of soap increases in water. As the temperature is increased the soap becomes soluble enough to form micelles this point is named the Krafft point. The temperature boundary at different soap concentrations above which micelles or hquid crystalline phases form is named the Krafft boundary (5). 

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