CTA+ ions

First of all, let ns make the assnmption that the overall solntion con-dnctivity (k) is entirely due to the free Br ions present in solution. That is, we assume that the conductivity due to the much larger CTA ions and the even larger micelles is negligible because of the size of these species (and hence large viscous drag). Thus we assume that... 

The reaction of Bromopyrogallol Red (BPR) (formula 4.21) with Mo(Vl) is not suitable for analytical use because the absorption maxima of the binary complex and of the reagent itself are too close. However, in the presence of cationic surfactants, bathochromic and hyperchromic effects are observed. These ternary systems allow a sensitive determination of molybdenum the absorbance of the reagent at the absorbance maximum of the ternary complex is insignificant [63-65]. The best results are obtained with the use of CTA ions. 

In our study (2) of the penetration of hexadecyltrimethylammonium bromide, CTAB, in egg-lecithin monolayers, we measured An and the surface density of the penetrating CTA+ ions. An was separated into its ideal and excess parts, and only the excess component was considered... 

Lecithin spread on CTAB solutions after equilibrium of CTA+ ions was achieved. 

Figure 1. Decrease of surface density of the CTA+ ions, as a function of...

Surface density of adsorbed CTAB. This was measured under the conditions as described above for surface tension using 14C labeled CTAB. Figure 1 represents the decrease in surface density of the CTA+ ions, Si, adsorbed from a given CTAB solution with the increase of the egg-lecithin surface density S2. The rate of this decrease was higher when the egg—lecithin molar fraction in the mixed film was below 0.34. 

Figure 4. Model of the mixed films of CTA+ ions and lecithin...

Figure 5. Surface pressure, n, of the mixed films, CTA+ ions + lecithin vs. the surface pressure, n2, of the pure lecithin monolayers...

Figure 6. Effect of CTA+ ions on the surface pressure of the lecithin monolayers. Surface pressure increase, AII2 vs. surface pressure, Ii2, of the pure lecithin monolayers.

Figure 7. Relative surface density of CTA+ ions, Sj/Sj0 X 100 vs. lecithin surface density y S2. Concentration of CTAB salt in bulk = 2 X 10 5M.

Curve 1 measured surface density of CTAB+ ions Curve 2 calculated surface density of CTA+ ions according to Equation 7... 

A related research concerns the competition of the n-type and type nucleophilic centers of CH3F for gaseous CTa ions (21). 

Based on the NMR and UV-Vis spectrophotometric results, the following models can be proposed for the four systems investigated (Fig. 8). Both Co(II) and Ni(II) atoms are retained at the interface in the different systems. More than one hexanol molecule enters the first coordination shell of Ni(II) ions. Co(II) interacts with one hexanol molecule in the CTAB-hexanol-water microemulsions, whereas both decanol and Triton X-100 molecules enter its first coordination shell. The Fe(III) ions are strongly hydrated in the inner water cores, and no hexanol molecules are able to replace the strongly held water molecules with this highly charged ion. Finally, the CTA ions interact indirectly only with the positively charged complexes. 

Fig. 11. (a) Isotherms for adsorption of cetyl trimethyl ammonium (CTA) ions onto -------------polystyrene, and-------O--------polystyrene latex particles. Abscissa log molar conc n CTA. Ordinate log... 

The values of potentials of adsorption of CTA ions and of parameter m were determined comparing the data shown in Fig. 37 with Eq. (44) using a computer procedure that ensures the best fit of the experimental and... 

Figure 20.16. Effect of increasing cetyltriammonium bromide (CTAB) concentration on the surface interactions of two glass surfaces. At low concentrations, there is a negative charge and double-layer interactions which decrease as the cationic CTA adsorbs. At higher concentrations, the double-layer force reappears due to a positive surface charge resulting from overcompensation by the CTA ions. Around the CMC, a barrier is observed corresponding to contact of head-groups from the two opposing surfaces (156)...

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