C critical micelle concentration

Test Methods. Surface tension (y) measurements were taken by Wil-helmy method (25+0.1°C). Critical micelle concentrations (cmc) were obtained from Y logC curves. Contact angle. Type GI, Japan. Wetting test. Canvas disk method, CIS,HG-2-380-66. Foam test, Ross-Miles lather method. Emulslbillty was determined by mixing 20 ml of 2.5%... 

Methods. All experiments were performed at 25°C. Critical micelle concentrations were determined using the maximum bubble pressure method on a SensaDyne 6000 surface tensiometer. Dry nitrogen was used as the gas source for the process and was bubbled through the solution at a rate of 1 bubble/sec. Cmc s measured using the Wilhemy plate method were in agreement with those obtained from the bubble tensiometer however, the bubble pressure method was used since it is less susceptible to error due to impurities and the nitrogen environment makes pH control easier. 

Critical micelle concentration (Section 19 5) Concentration above which substances such as salts of fatty acids aggre gate to form micelles in aqueous solution Crown ether (Section 16 4) A cyclic polyether that via lon-dipole attractive forces forms stable complexes with metal 10ns Such complexes along with their accompany mg anion are soluble in nonpolar solvents C terminus (Section 27 7) The amino acid at the end of a pep tide or protein chain that has its carboxyl group intact—that IS in which the carboxyl group is not part of a peptide bond Cumulated diene (Section 10 5) Diene of the type C=C=C in which a single carbon atom participates in double bonds with two others... 

P. Mukerjee and M. J. Mysels, Critical Micelle Concentration ofMqueous Suf actant Systems, NSROS-NBS 36, U.S. Dept, of Commerce, Washiagton, D.C., 1971. 

K is K, just below the collectors critical micelle concentration, C,. Ko is Ki at some higher cohector concentration, C,. E is the relative effectiveness, in adsorbing cohigend, of surface cohector versus micehar collector. Generally, E > 1. F, is the surface excess of collector. More about each K is avahable [Lemhch, Adsubble Methods, in Li (ed.). Recent Developments in Separation Science, vol. 1, CRC Press, Cleveland, 1972, pp. 113-127 Jashnani and Lemlich, Ind. Eng. Chem. Process Des. Dev., 12, 312 (1973)]. 

One of the most important characteristics of the emulsifier is its CMC, which is defined as the critical concentration value below which no micelle formation occurs. The critical micelle concentration of an emulsifier is determined by the structure and the number of hydrophilic and hydrophobic groups included in the emulsifier molecule. The hydrophile-lipophile balance (HLB) number is a good criterion for the selection of proper emulsifier. The HLB scale was developed by W. C. Griffin [46,47]. Based on his approach, the HLB number of an emulsifier can be calculated by dividing... 

Figure 20 shows the plot of the surface tension vs. the logarithm of the concentration (or-lg c-isotherms) of sodium alkanesulfonates C,0-C15 at 45°C. In accordance with the general behavior of surfactants, the interfacial activity increases with growing chain length. The critical micelle concentration (cM) is shifted to lower concentration values. The typical surface tension at cM is between 38 and 33 mN/m. The ammonium alkanesulfonates show similar behavior, though their solubility is much better. The impact of the counterions is twofold First, a more polarizable counterion lowers the cM value (Fig. 21), while the aggregation number of the micelles rises. Second, polarizable and hydrophobic counterions, such as n-propyl- or isopropylammonium and n-butylammonium ions, enhance the interfacial activity as well (Fig. 22). Hydrophilic counterions such as 2-hydroxyethylammonium have the opposite effect. Table 14 summarizes some data for the dodecane 1-sulfonates.

The poor solubility of higher sodium alkanesulfonates cited above is reflected in the surface tension vs. concentration plots of sodium pentadecane 4-sulfonate (Fig. 26). Because below the critical micelle concentration the solubility limit is reached, a break in the a-c plot occurs. The problem of solubility properties of alkanesulfonates below the point at which the hydrated crystals or solid... 

Sanchez et al. [61,62] studied the stability of sodium decyl, dodecyl, and tetradecyl sulfates and sodium lauryl ether (3 EO) sulfate in acid media (pH 1) at different temperatures and concentrations above and below the critical micelle concentration. Sodium decyl sulfate was shown to be relatively stable for several hours at temperatures up to 90°C. Sodium dodecyl and tetradecyl sulfates were only stable for short periods of time at temperatures above 40-50°C. As expected, sodium lauryl ether sulfate was less stable to hydrolysis than the corresponding lauryl sulfate. 

Table 17 shows the CMCs of sodium alcohol propoxysulfates at 20°C determined from surface tension measurements by the maximum bubble pressure [127] and Table 18 shows the critical micelle concentrations of sodium pro-poxylated octylphenol and propoxylated nonylphenol sulfates. Surface tension... 

As an even more explicit example of this effect Figure 6 shows that EPM is able to reproduce fairly well the experimentally observed dependence of the particle number on surfactant concentration for a different monomer, namely methyl methacrylate (MMA). The polymerization was carried at 80°C at a fixed concentration of ammonium persulfate initiator (0.00635 mol dm 3). Because methyl methacrylate is much more water soluble than styrene, the drop off in particle number is not as steep around the critical micelle concentration (22.) In this instance the experimental data do show a leveling off of the particle number at high and low surfactant concentrations as expected from the theory of particle formation by coagulative nucleation of precursor particles formed by homogeneous nucleation, which has been incorporated into EPM. 

An amphiphilic molecule has a single positively charged head group and is in solution with a concentration of 10 mM. If the critical micelle concentration of the molecule is 25 mM and the Krafts temperature is 25°C ... 

Table 2 Critical Micelle Concentration of Some Surfactants (aqueous solutions at 25°C)...

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