Surface tension depression

Gramicidin decreases the surface tension of aqueous solution77. The bactericidal and hemolytic properties of gramicidin were destroyed by heat but the surface tension depression was not changed. 

This brief review has attempted to discuss some of the important phenomena in which surfactant mixtures can be involved. Mechanistic aspects of surfactant interactions and some mathematical models to describe the processes have been outlined. The application of these principles to practical problems has been considered. For example, enhancement of solubilization or surface tension depression using mixtures has been discussed. However, in many cases, the various processes in which surfactants interact generally cannot be considered by themselves, because they occur simultaneously. The surfactant technologist can use this to advantage to accomplish certain objectives. For example, the enhancement of mixed micelle formation can lead to a reduced tendency for surfactant precipitation, reduced adsorption, and a reduced tendency for coacervate formation. The solution to a particular practical problem involving surfactants is rarely obvious because often the surfactants are involved in multiple steps in a process and optimization of a number of simultaneous properties may be involved. An example of this is detergency, where adsorption, solubilization, foaming, emulsion formation, and other phenomena are all important. In enhanced oil recovery. 

Additions of substances for surface tension depression (ocenol, PEG, CMC TS.20, see Table 1 of Part I) induced a significant reduction of the mass transfer coefficient (by... 

Bioaccumulation All classes of surfactant are active surface tension depressants. At the critical micelle concentration (CMC) abrupt changes occur in the characteristic properties of surfactants such that surface and interfacial tensions in an aqueous system are at their minimum while osmotic pressure and surface detergent properties are significantly increased. The CMC for most surfactants is reached around 0.01% (18, 19). These effects have an impact on the potential for bioaccumulation of the pesticide, and in the organisms monitored the presence of Dowanol and nonylphenol increased the accumulation of fenitrothion and aminocarb at least 20-300% respectively, over the accumulation obtained in their absence (20). In effect, these adjuvants... 

Therefore, in a liquid system, a diffusion of gas takes place from the small bubbles into the large bubbles, resulting in the disappearance of the small bubbles, while the large bubbles grow in size with time. It is also apparent that low values of y, e.g. by addition of a surface-tension depressant such as a silicone surfactant, reduce the pressure differences between bubbles of different sizes and hence lead to better bubble stability and small average cell size. 

Still, other researchers explained the discrepancy between theoretical and experimental bubble-points with surface tension depression. It is true that most manufacturers treat their membranes with wetting agents. It is conceivable that these surfactants can dissolve in the test fluid and lower the surface tension. 

W. P. Larson, H. O. Halvorson, R. D. Evans, and R. G. Green, The effect of surface tension depressants upon bacterial toxins, in Third Colloid Symposium Monograph, 1925, pp. 152-157. 

Uses Detergent surface tension depressant wetting agent in textiles. 

Extensively studied nonionic surfactants are PDMS / polyether block copolymers [31] and poly(ethylene oxide) substituted trisiloxanes [32-35]. They are able to achieve a maximum surface tension depression to about 21 mN/m and a low critical micelle concentration (CMC) [36], These siloxane surfactants can self-assemble into a variety of... 

Disodium nonoxynol-10 sulfosuccinate surface tension depressant, textile emulsions Disodium nonoxynol-10 sulfosuccinate surface tension reducer Cyclomethicone Tyloxapol surface tension reducer, agric. 

Accordingly, after high-speed mixing, vacuum or dryers are used to release air. The purpose of the defoamer or air release agent is to speed up and optimize the removal of air. Some can help prevent air entrapment. The agents also serve as lubricants for the fillers, as wetting agents, and as surface tension depressants —-all of which contribute to the air release function. 

Control means other than ventilation. Tank covers, foams, beads, chips, or other materials floating on the tank surface so as to confine gases, mists, or vapors to the area under the cover or to the foam, bead, or chip layer or surface tension depressive agents added to the liquid in the tank to minimize mist formation, or any combination thereof, may all be used as gas, mist, or vapor control means for open-surface tank operations, provided that they effectively reduce the concentrations of hazardous materials in the vicinity of the worker below the limits set in accordance with paragraph (i)(2) of this section. 

Good wetting agent and surface tension depressant. 

Surfactants, by definition, are substances which lower the surface tension of liquids in which they are dissolved or the interfacial tension between two or more mutually immiscible phases. It has long been recognised that the most effective surface tension depressants contain highly water-attracting (hydrophilic) and highly water-repellent (hydrophobic) groups, joined together in the same molecule. 

Measurements of surface tension depression in aqueous extracts of collected aerosol particles [25-31], fogwater [27,28, 32], and rainwater [33] have in general shown decreasing surface tensimi with increasing organic concentration, with increased surface tension depression in samples collected in more polluted regions. The results of several studies are summarized in Fig. 4. 

The surface tension of rainwater, melted snow, and atmospheric particles was sampled 1979-1981 in Frankfurt/Main by Seidl and Hanel [195]. They found that concentrations of both soluble and insoluble organic material were too small (normalized to 2 x 10 and 2.5 x 10 mol L respectively) to affect both water uptake and loss, but that there was slight surface tension depression. They suggested that in areas with higher urban pollution, these effects might be enhanced. 

Capel et al. collected urban area fog water in Diibendorf, Switzerland (near Zurich) over a period of 6 nights in November-December 1986-1987 [196]. The samples (tested at 20 °C) showed increasing surface tension depression with increasing organic concentration. Most of the organic material remained unspeciated however, alkanes, biphenyls, alkylbenzenes, formate, and acetate were detected. 

Moore et al. measured the surface tension of oceanic dissolved organic matter (DOM) from Atlantic Ocean samples off the coast of Georgia, USA [197]. Using pendant drop tensiometry at 24 C they saw clear surface tension depression from surface-active organics, which followed the Szyszkowski-Langmuir equation, = ffo — 2.9527 In (1 -i- 2 x 10 C), where C is in units mg L . Surface tension as inferred using KTA also showed excellent agreement with the direct measurements. 

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