Emulsifying action

Detergent. A substance that reduces the surface tension of water. It works at oil/water interfaces and has an emulsifying action, enabling it to... 

A water-soluble blue can be manufactured by adding pepticizing agents (the latter improve the water solubility via an emulsifying action). This forms a transparent colloidal solution in water without the use of high shear forces [3.180],... 

While the variability has been assessed for LAS, little is known for other surfactants. However, the variability of the log Kow-values of LAS indicates that Kow measurements yield conditional partition ratios rather than well defined partition coefficients. On thermodynamic grounds, the partition ratio for ionic surfactants is a parameter depending very much on the electrolyte composition of the aqueous medium and therefore cannot be viewed as a partition coefficient in the sense of Henry s law (Schwarzenbach et al. 1993). In addition, experimental determination of Kow of surfactants could yield erroneous results, due to the emulsifying action of the surfactants in the octanol-water system (Morall et al., 1997). 

M. J. Groves and de D. A. Galindez, The self-emulsifying action of mixed surfactants in oil, Acta. Phartn. Suec. 13 361-372 (1976). 

Partially hydrolyzed lecithins exhibit enhanced oil-in-water emulsifying properties, particularly in the presence of calcium and magnesium ions. They do not lose their emulsifying action in the presence of calcium and magnesium ions as rapidly as do the unmodified types. Enzymatically modified lecithins have been used in calf milk replacement formulations to improve the emulsification and digestibility of fats (56). 

Nonionic detergents stimulated growth on hexadecane Emulsifying action permits effective contact between cells and substrate 30... 

Enhanced rate of biodegradation of PCBs in ligninsulfonate emulsion Emulsifying action overcomes interfacial area limitation 31... 

Increased rate of hydrocarbon degradation Emulsifying action increases interfacial area 32... 

Problems can arise when "hard" water is used for cleaning because the high concentrations of Ca"+ and Mg"+ in such water cause fatty acid salts to precipitate. Not only does this interfere with the emulsifying action of the soap, it also leaves a hard scum on the surface of sinks and tubs. 

The degree of hydrolysis of poly(vinyl alcohol) influences the emulsion polymerization of vinyl acetate. The lower the degree of hydrolysis, the better the emulsifying action of the protective colloid and the faster the rate of polymerization [146]. In coimection with this statement we must point out that the terminology a poly(vinyl alcohol) of low degree of hydrolysis is widely... 

Although small amounts are used, emulsifiers that act as surface-active agents or surfactants can have a significant effect on the surface behavior of the system in which they are placed. The chemistry of the emulsifying action generally involves the use of a material that has a molecule, or ion, that contains a hydrophific group at one end and a hydrophobic group at the other end. 

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). 

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. 

Cationic surfactants such as dodecylammonium chloride (DAC), cetyltrimethylammonium bromide (CTAB), and dodecyltrimethylam-monium bromide (DTAB) are much less frequently used than anionic surfactants due to their relatively inefficient emulsifying action or adverse effects on initiator decomposition. In addition, the cationic surfactants are much more expensive than anionic surfactants. 

The emulsifying effect of whole egg or egg yolk alone is utilized, for example, in the production of mayonnaise and of creamy salad dressings (cf. 14.4.6). Phospholipids, LDLs and proteins are responsible for the emulsifying action of eggs. 

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