Solubilization gases

Micelles can solubilize gases. It has been demonstrated [49] that the Laplace model gives a good description of such solubilization for the case of ionic micelles ... 

It is well known that surfactants dissolved in aqueous solutions serve to enhance the solubility of ordinarily insoluble organic compounds, both solids and liquids. This phenomenon, commonly referred to as solubilization (ref. 501), has important commercial applications and as a consequence, has been the subject of considerable research (for reviews see ref. 450,502-504). Yet, as King and co-workers point out (ref. 501,505,506), less well known is the long-recognized fact that micellar solutions of surfactants are also capable of solubilizing gases (and vapors of low-molecular-weight compounds) in much the same manner as... 

Cb 0 (i.e., 4>b 0 at = 1), which implies that the liquid contains vanishingly small amounts of the mobile component (i.e., this condition is applicable to solubilized gases and volatile liquid-phase products generated by chemical reaction), or... 

Formaldehyde is a colorless gas that is soluble in water (3). Commercial aqueous preparations of formalin contain 37 0% w/w solubilized gas. They also contain formic acid (<0.05%) and 10-15% methanol, which is added to prevent the polymerization of formaldehyde into paraformaldehyde (3,11). Methanol and formic acid make these solutions an unacceptable fixative for fine structures (9). Paraformaldehyde is a polymerized form of formaldehyde that dissociates at 60°C and neutral pH. Freshly prepared solutions of paraformaldehyde are preferred for most immunochemical procedures because they provide a fixative free of extraneous additives and are usually the conservative fixatives of choice when beginning the development of a fixation protocol (3,5). 

The solubility of compressed gasses in liquids is usually quite high.. Dependent on pressure and temperature concentrations of highly compressible media between 5 - 50 % by weight can be dissolved in the solute (liquid). Due to the solubilized gas the properties of the liquid are changed. 

These solvents differ in volatility and selectivity for the removal of H2S, mercaptans, and CO2 from gases of different composition. Other alkaline solvents used for the absorption of acidic components in gases include potassium carbonate, K CO, solutions combined with a variety of activators and solubilizers to improve gas—Hquid contacting. 

The development of CO2 fixation reactions in supercritical CO2 attracts increasing attention due to its gas-like low viscosities and high diffusivities and its liquid-like solubilizing power. Matsuda et al. attempted to carry out the con-... 

Q = saturation solubility of drug (macroparticles) y = interfacial tension between drug particles and the solubilizing fluids M = Molecular weight of the drug r = radius of the microscopic drug particle R = ideal gas constant... 

These optimum methanol-water mixtures as solvents for the water gas shift reactions represent compromises between a high concentration of the reactant water and a high concentration of methanol to solubilize the CO and metal carbonyls. Furthermore, all of the solvent mixtures used in this work contain amounts of water which are large relative to that consumed in the water gas shift reaction. Therefore, the concentration of water may be regarded as a constant during the water gas shift reactions conducted in this research project. 

What characterizes surfactants is their ability to adsorb onto surfaces and to modify the surface properties. At the gas/liquid interface this leads to a reduction in surface tension. Fig. 4.1 shows the dependence of surface tension on the concentration for different surfactant types [39]. It is obvious from this figure that the nonionic surfactants have a lower surface tension for the same alkyl chain length and concentration than the ionic surfactants. The second effect which can be seen from Fig. 4.1 is the discontinuity of the surface tension-concentration curves with a constant value for the surface tension above this point. The breakpoint of the curves can be correlated to the critical micelle concentration (cmc) above which the formation of micellar aggregates can be observed in the bulk phase. These micelles are characteristic for the ability of surfactants to solubilize hydrophobic substances in aqueous solution. So the concentration of surfactant in the washing liquor has at least to be right above the cmc. 

The ease of solubilizing the analyte is a key factor also. This is because the easier it is to get the solute to these potential equilibration points inside the chromatographic column when the fluid is moving with high diffusivity, the faster the equilibrations or separation can take place. Compared to a gas where the solubilities of the analytes of... 

Liotta and Grisdale (1975) have reported on the relative nucleophilicities of anions whose potassium salts were solubilized into acetonitrile by 18-crown-6 [3]. The results (Table 28) show the sequence Nj > OAc- > CN- > F- > Cl-x Br- > I- > SCN-, which is very different from the reactivity scale in water CN- > I- >SCN- > Nj > Br- > Cl- > OAc- > F-. Furthermore, the relative nucleophilicities in acetonitrile vary only by a factor of 30, whereas in water they differ by as much as a factor of 1000. The fact that gas-phase nucleophilicities also span a narrow range led the authors to conclude that anion solvation is much less important in acetonitrile than in water. The values recently reported by Lemmetyinen et al. (1978) for the relative nucleophilicities of anions towards methyl methanesulfonate in benzene show the same sequence as in protic solvents, however. The authors offered no explanation for this peculiar behaviour. 

Fig. 8.20 Solubilization rate of trichloroethylene as affected by surfactant type and concentration Cs and C denote surfactant concentration and initial surfactant concentration, respectively. Reprinted from Zhong L, Mayer AS, Pope GA (2003) The effects of surfactant formulation on nonequUibrium NAPL solubilization. J Contam Hydrol 60 55-75. Copyright 2003 with permission of Elsevier.

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