Aqueous surfactant solutions values

Values given for 1.0% aqueous surfactant solutions. value in pure... 

A 1.5% by weight aqueous surfactant solution has a surface tension of 53.8 dyn/cm (or mN/m) at 20°C. (a) Calculate a, the area of surface containing one molecule. State any assumptions that must be made to make the calculation from the preceding data, (b) The additional information is now supplied that a 1.7% solution has a surface tension of 53.6 dyn/cm. If the surface-adsorbed film obeys the equation of state ir(o - 00) = kT, calculate from the combined data a value of 00, the actual area of a molecule. 

The CMC of commercial AOS and other surfactants at 40°C has been determined by Gafa and Lattanzi [6] who plotted the surface tension of aqueous surfactant solutions against concentration. The surface tensions were determined with the ring method according to du Nouy. Table 5 gives their CMC values in mmol/L and the surface tension at the CMC in mN/m. Table 5 also contains CMC values of isomerically pure sodium alkyl sulfates, sodium alkylbenzene-sulfonates, sodium hydroxyalkanesulfonate, and sodium alkenesulfonates at 40°C, taken from the literature [39 and references cited therein]. 

Thermal conductivity and capacity of aqueous surfactant solutions in the concentration range 130 to 1,060 ppm did not differ from that of pure water (Hetsroni et al. 2001b). Figure 2.53 shows the dependence of thermal conductivity k on the temperature for C = 530 ppm Habon G solution. The value of the thermal conductivity agrees well with that for pure water within the standard deviation of 2%. 

Figure 1 shows the change in fluorescence intensity of ANS in the aqueous surfactant solution. In the case of the hydrocarbon surfactant, the fluorescence intensity of ANS was proportional to the surfactant concentration above the CMC. Since the fluorescence intensity of ANS had a constant value below the CMC, the inflection point appeared at the CMC. The surfactant concentration at the inflection pojnt nearly coincided with the CMC of 6ED and SDS( the CMC was 6x10 mole/1 for 6ED and 8.5x10 mole/1 for SDS). These findings indicate that ANS is solubilized into the hydrocarbon surfactant micelles. Further, above the CMC, the fluorescence intensity of ANS in 6ED solution was about ten-fold larger than in SDS solution. Since both ANS and SDS are anionic, the lower solubility of ANS in SDS micelles is probably due to the electric... 

The primary results in Table I may also be processed to yield values of the benzene activity coefficient in the Intramicellar solution, Tg, defined as fg/(fg Xg), where fg is the fugacity of benzene in equilibrium with the aqueous surfactant solution, and fg is the fugacity of pure benzene at the given temperature. Figures 1-4 are plots of the solubilization constant (K) and the benzene activity coefficient (Tg) against the intramicellar mole fraction of benzene (Xg) for the surfactants CPC and SDS at the Indicated temperatures. 

Another important result should also be mentioned the rupture of unstable films and formation of black spots occur at the same critical thickness around 30 nm (grey films) for films from aqueous surfactant solutions [54], Fig. 3.13 plots the dependence of the most probable values of hcr and hcr,bi at which black spots form in the grey film. The dispersity of hcr values 0.2 nm can serve as an estimate of the data accuracy. 

More complex with respect to molecular interaction is the case of formation of non-aqueous films on the surface of aqueous solutions from non-ionic surfactants [528], Films from octane were obtained by adsorption from drops of octane/non-adsorbing diluent (squalane) mixture. Occasionally the spreading of alkanes on aqueous surfactant solution gives stable thin oil films (e.g. on solutions of the anionic surfactants Aerosol OT) [529,530], Some evidence about the stability of asymmetric films can be derived from the data about the surface pressure and spreading coefficients of liquids on water surface. These data are known for many organic liquids [531,532], It should be also noted that the techniques for determination of the spreading coefficients have improved considerably [533,534]. Most precise values were obtained by measuring the surface pressure of a monolayer with a special substance introduced as an indicator [533]. 

Schanze, K. S., Mattox, T. E, and Whitten, D. G. (1982). Correlation of the rate of thermal cis-trans isomerization of p-nitro-p -dialkylaminoazobenzenes with solvent Z value applied to study polarity in aqueous surfactant solutions. ]. Am. Ghem. Soc. 104, 1733-1735. 

Table Ila. Values for the Equilibrium Shear Modulus Gq for Different Aqueous Surfactant Solutions...

Application of Eq. 5.4 to experimental data [13] led to values for linear coefficients of around 0.5, which is lower than 0.67, the theoretical value. The difference between the theoretical and experimental values can be explained in terms of the contact angle, which is greater than zero in the aqueous surfactant solutions used in the experiments. The decrease in liquid tension tends towards lower linear coefficients. For most practical situations, the following coefficients can be assumed 0.5 for aqueous surfactant solutions, 0.35 for most organic liquids and 0.6 for water without surfactant [13]. These numbers demonstrate the need for surfactant addition in most analytical procedures implemented in segmented flow systems, and Brij-35 (1.0 ml L-1 polyoxyethylene lauryl ether2 solution) is by far the mostly commonly used surfactant [16]. 

When non-aqueous surfactant solutions are used to remove soils from fabrics, furs, leathers (so-called dry-cleaning process), solubilisation is a quite necessary and sufficient condition for the soil removal considering sufficiently low CMC values. The same also applies to washing of metal surfaces where surfactant additives are often added both to polar (alcohols, ketones, etc.) and non-polar media (aliphatic or aromatic hydrocarbons and their mixtures). 

The basicities in water and in aqueous surfactant solution of another 15 aryl-Pl(pyrrolidino) [(NC4Hs)3P=N-Ar] and aryl-Pl(dimethylamino) [(NMe2)3P=N Ar] phosphazenes (Ar = mono or di substituted phenyl rings) have been measured and correlated with previous data using acetonitrile and THE. A comparison with other bases such as guanidines, amines and pyridines showed that, in all cases, the phosphazenes were the strongest bases. The results confirmed earlier conclusions about the partly ylidic character of the NP double bond. Density functional theory calculations have shown that the phosphazenes (41) and (42) are very powerful neutral organic superbases at the site marked by an asterisc (the calculated pA a values in acetonitrile were 44.8 and 37.8, respectively). ... 

Fig. 4 Calculated adhesion tension values of aqueous surfactant solutions with different concentrations...

At less than half the value of the coefficient of evaporation (K = 2 x 10 " cm /s), when higher relative vapor pressurep/ps = 0.54 was maintained in the chamber, there was no marked difference in the rate of evaporation of pure water and aqueous surfactant solutions (curve 3). Probably, in this case... 

Surfactant values are at the critical micelle concentration (CMC) in aqueous solution surfactant/defoamer values are at 0.1% concentration in aqueous solution. 

Tests were performed at 75°C using a University of Texas Model 500 spinning drop tensiometer. Active surfactant concentration in the aqueous phase prior to oil addition was 0.50% wt. The Kem River crude oil was from the Patricia Lease. The pH of the deionized water surfactant solutions was 8. The pH of the aqueous NaCl surfactant solutions was 9.5 unless otherwise noted. values represent the average deviation of two or three measurements at different times (0.75-1 h apart). D.I., deionized. 

Surfactant blends of interest will exhibit clouding phenomena in aqueous solutions undergoing a phase transition from a one phase system to a two phase system at a discrete and characteristic temperature, referred to as the Cloud Point (CP). This value indicates the temperature at which sufficient dehydration of the oxyethylene portion of the surfactant molecule has occurred and this results in its "displacement" from solution. The addition of lyotropic salts will depress the CP, presumably due to the promotion of localised ordering of water molecules near the hydrophilic sheath of the surfactant molecule (8). Furthermore, the addition of different oils to surfactant solutions can induce either an elevation or a depression of the recorded CP and can be used to qualitatively predict the PIT (8x9). 

In Table 3 are the values of surface tension for the aqueous LAS homolog solutions. Values of molar volume used are those for the pure LAS homolog independent of water. The justification for this comes from the Winsor R model (20, 21) and work by Scriven and Davis (30) who showed that accurate CED values can be obtained from a statistical mechanical treatment of an interface using only 2 or 3 atomic or molecular layers of that interface. For a surfactant solution, the surfactant will predominate in the interface, hence the choice of pure LAS for the solution molar volumes. 

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