Mixtures, binary solvent

Figure 16. Graphs Showing the Distribution Coefficient of n-PentanoI between Water and Three Binary Solvent Mixtures Plotted against Solvent Composition...

Practically a more convenient way of expressing solute retention in terms of solvent concentration for a binary solvent mixture as the mobile phase is to use the inverse of equation (11), i.e.. 

The bulk properties of mixed solvents, especially of binary solvent mixtures of water and organic solvents, are often needed. Many dielectric constant measurements have been made on such binary mixtures. The surface tension of aqueous binary mixtures can be quantitatively related to composition. ... 

Langhals has described a remarkable relationship of most of the empirieal solvent parameters [Z. t (30), Y, ete.] to composition in binary solvent mixtures ... 

In our discussion of the coexistence curve, we tacitly assumed that at least one liquid phase can exist for any composition. However, since component 2 is a supercritical gas, the physically allowable liquid compositions are limited by the solubility of the gas in the binary solvent mixture. As the pressure rises, the solubility of the gas increases, thereby enlarging the composition range which permits the existence of a liquid phase. 

They showed further that the limiting slope (RTA2) of the plot of the osmotic pressure-concentration ratio tz/c against the polymer concentration in a binary solvent mixture should be proportional to the value of the quantity on the left side of Eq. (17),f with V2 representing the volume fraction of solvent in the nonsolvent-solvent mixture which is in osmotic equilibrium with the solution. The composition of the liquid medium outside the polymer molecules in a dilute solution must likewise be given by V2. The composition of the solvent mixture within the domains of the polymer molecules may differ slightly from that outside owing to selective absorption of solvent in preference to the nonsolvent. This internal composition is not directly of concern here. If the solution is made sufficiently dilute, the external nonsolvent-solvent composition v2 = l—Vi) will be practically equal to the over-all solvent composition for the solution as a whole. Hence... 

Recently, Janjic et al. published some papers [33-36] on the influence of the stationary and mobile phase composition on the solvent strength parameter e° and SP, the system parameter (SP = log xjx, where and denote the mole fractions of the modiher in the stationary and the mobile phase, respectively) in normal phase and reversed-phase column chromatography. They established a linear dependence between SP and the Snyder s solvent strength parameters e° by performing experiments with binary solvent mixtures on silica and alumina layers. 

FIGURE 4.10 Mobile phase selection by microcircular technique, a. Sample of known composition A = nonpolar compound A1 = n-hexane A2 = acetone A3 = n-hexane-acetone, 60-1-40, v/v B = polar compound B1 = methanol B2 = water B3 = methanol-water, 70-1-30, v/v. b. Sample of unknown composition testing with solvents of different Snyder s groups and binary solvent mixture. 

LDPE Chimassorb 944 Various binary solvent mixtures [458]... 

In the resulting binary solvent mixtures of either OSM or TSM micronising step procedures, one apolar component (n-hexane or n-heptane) serves to give high swelling-melting power to the polymer but does not heat under microwave irradiation. The second polar component (ethyl acetate, acetone, and isopropyl alcohol) has... 

Jozefowicz M (2007) Determination of reorganization energy of fluorenone and 4-hydroxy-fluorenone in neat and binary solvent mixtures. Spectrochim Acta A 67 444-449... 

Special care has to be taken if the polymer is only soluble in a solvent mixture or if a certain property, e.g., a definite value of the second virial coefficient, needs to be adjusted by adding another solvent. In this case the analysis is complicated due to the different refractive indices of the solvent components [32]. In case of a binary solvent mixture we find, that formally Equation (42) is still valid. The refractive index increment needs to be replaced by an increment accounting for a complex formation of the polymer and the solvent mixture, when one of the solvents adsorbs preferentially on the polymer. Instead of measuring the true molar mass Mw the apparent molar mass Mapp is measured. How large the difference is depends on the difference between the refractive index increments ([dn/dc) — (dn/dc)A>0. (dn/dc)fl is the increment determined in the mixed solvents in osmotic equilibrium, while (dn/dc)A0 is determined for infinite dilution of the polymer in solvent A. For clarity we omitted the fixed parameters such as temperature, T, and pressure, p. 

In dealing with binary solvent mixtures it is necessary to dis-... 

Binary solvent mixtures provide a simple means of controlling solvent strength but limited opportunities for controlling solvent selectivity. With ternary and quaternary solvent mixtures, it is possible to fine-tune solvent selectivity while maintaining a constant solvent strength [105-107]. In addition, there are only a small number of organic modifiers that can be used as binary mixtures with water. 

Jozefowicz M, Heldt JR (2003) Preferential solvation of fluorenone and 4-hydroxyfluore-none in binary solvent mixtures. Chem Phys 294 105-116... 

Solvatochromism and piezochromism of a range of pentacyanoferrates(II) have been examined in binary aq ueous solvent mixtures, " and their solvatochromism in micelles and reversed micelles. The solvatochromism of [Fe(CN)5(nicotinamide)] has been established in several ranges of water-rich binary solvent mixtures, " of [Fe (CN)5(2,6-dimethylpyrazine)] in acetonitrile-water mixtures.The solvatochromism of [Fe(CN)5(4Phpy)] and [Fe(CN)5(4Bu py)] has been proposed as an indicator of selective solvation in binary aqueous solvent mixtures. ... 

Sirieix-Plenet, ]., Gaillon, L., and Letellier, R, Behaviour of a binary solvent mixture constituted by an amphiphilic ionic liquid, l-decyl-3-methylimidazolium bromide and water. Potentiometric and conductimetric studies, Talanta, 62, 979,... 

The effect of salts on the vapor-liquid equilibrium of solvent mixtures has been of considerable interest in recent years. Introduction of a salt into a binary solvent mixture results in a change in the relative volatility of the solvents. This effect can be used to an advantage where the separation of the solvents is of interest. Furter and co-workers have demonstrated the potential importance of salts as separating agents in extractive distillation (J, 2, 3). 

Two approaches have been used in correlating the phase equilibrium behavior of complex mixtures involving a non-volatile salt dissolved in a binary solvent mixture. Johnson and Furter (i) developed what appears to be the most popular approach by correlating the ratio of relative volatilities of the solvents as a function of salt concentration. Meranda and Furter (2) review this approach and present experimental determinations of the necessary parameters as a function of mole fraction of one of the solvents. 

On examination of Equations 14 and 16, it is clear that estimates of vapor pressure lowering and ks are all that are required to determine the influence of a given salt on the vapor-liquid equilibrium behavior of a binary solvent mixture. 

Tables IV-XVI show that the tetraalkylammonium salts have a large effect on both solvents in the binary solvent mixture, especially the larger tetraalkylammonium bromides, i.e., (n-C3H7)4NBr and (n-C4Hg)4NBr. This can be seen from consideration of the boiling temperature alone. This observation is also borne out by the surface tensions and solubilities at 25°C of the individual salts studied, the results of which are tabulated in Table XVII in water, in ethanol, and in an ethanol-water mixture at x = 0.206. For the higher homologs of the R4NBr series, these salts exert a large effect on the surface tensions of the solvent systems studied and show a marked increase in their solubility in ethanol.

In Table XVIII, there are several trends that can be noted in k if one proceeds through the R4NBr series. First of all, k tends to decrease as the size of the TAA cation increases and, in fact, tetra-n-butylammonium bromide shows a large salting-in effect. This trend is emphatically demonstrated by Figure 13, which shows the smoothed salt effects of the various salts studied in the ethanol-water system at x = 0.206. Secondly, it appears that there is a larger salting-out effect as the mole fraction of ethanol increases in the binary solvent mixture. 

Thermodynamics of Preferential Solvation of Electrolytes in Binary Solvent Mixtures... 

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