Mutual solubility of solvents

The meaning of the surface excess is illustrated in Fig. 1, in which the solid line represents the actual concentration profile of an adsorbate i, when the bulk concentration of i in the phase a (a = O or W) is c . The hatched area corresponds to be the surface excess of i, T,. This quantity depends on the location of the dividing surface. On the other hand, the experimentally accessible quantity should not depend on the location of the artificially introduced dividing surface. The relative surface excess, which is independent of the location of the dividing surface, is defined by relativizing it with respect to those of certain reference components. In oil water interfaces, the mutual solubility of solvents can be significant. The relative surface excess in Eq. (3) is then related to the surface excesses through... 

T. Michalowski, Effect of Mutual Solubility of Solvents in Multiple Liquid-Liquid Extraction, /. Chem. Ed. 2002, 79, 1267. 

Related to the mutual solubility of solvents with water is their lipophilicity or hydrophobicity that can be described by (the logarithm of) their partition coefficient between n-octanol and water, log. The more hydrophobic a substance is, the larger... 

In the models presented below, it is assrrmed that the D+T systerrrs are homogeneous in the entire range of variation of the mole fraction x in the mixture this mearts the unlimited, mutual solubility of solvents forming the binary-solvent system and the complete solubility of the substrates and reaction products, at pre-assumed concentrations of the solutes. 

If the mutual solubilities of the solvents A and B are small, and the systems are dilute in C, the ratio ni can be estimated from the activity coefficients at infinite dilution. The infinite dilution activity coefficients of many organic systems have been correlated in terms of stmctural contributions (24), a method recommended by others (5). In the more general case of nondilute systems where there is significant mutual solubiUty between the two solvents, regular solution theory must be appHed. Several methods of correlation and prediction have been reviewed (23). The universal quasichemical (UNIQUAC) equation has been recommended (25), which uses binary parameters to predict multicomponent equihbria (see Eengineering, chemical DATA correlation). 

Example 4 Shortcut Calculation Case B Let iis solve the problem in Example 2 hy assuming case B. The solute (acetic acid) concentration is low enough in the extract so that we may assume that the mutual solubilities of the solvents remain nearly constant. The material balance can be calculated by an iterative method. 

Synthesis. The procedures used for the preparation of other amphiphilic networks (1) could not be used for the synthesis of PHEMA-1-PIB because of the insolubility of PHEMA in solvents that dissolve PIB e.g., THF. The above described silylation-desilylation procedure was designed to provide mutual solubility of the phases and thus to make the synthesis possible. 

A large volume (11.25 m3) of mixed fatty acids was to be bleached by treatment with successive portions of 50 wt% hydrogen peroxide. 2-Propanol (450 1) was added to the acids (to improve the mutual solubility of the reactants). The first 20 1 portion of peroxide (at 51°C) was added, followed after 1 min by a second portion. Shortly afterwards an explosion occurred, which was attributed to spontaneous ignition of a 2-propanol vapour-oxygen mixture formed above the surface of the liquid. Oxygen is almost invariably evolved from hydrogen peroxide reactions, and volatile flammable solvents are therefore incompatible components in peroxide systems. 

Likewise, the following Table 27.1, records the mutual solubilities of a few typical solvent pairs that are used frequently for liquid-liquid extraction procedures. 

Table 2.2 Mutual Solubility of Water and Some Organic Solvents at 25°C... 

Solvent extraction rarely involves gases, so that other cases should now be considered. Most liquid organic solutes are completely miscible with, or at least highly soluble in, most organic solvents. The case of a liquid solute that forms a solute-rich liquid phase that contains an appreciable concentration of the solvent is related to the mutual solubility of two solvents, and has been discussed in section 2.2. This leaves solid solutes that are in equilibrium with their saturated solution. It is expedient to discuss organic, nonelectrolytic solutes separately from salts or other ionic solutes. 

Given a nonionic solute that has a relatively low solubility in each of the two liquids, and given equations that permit estimates of its solubility in each liquid to be made, the distribution ratio would be approximately the ratio of these solubilities. The approximation arises from several sources. One is that, in the ternary (solvent extraction) system, the two liquid phases are not the pure liquid solvents where the solubilities have been measured or estimated, but rather, their mutually saturated solutions. The lower the mutual solubility of the two solvents, the better can the approximation be made. Even at low concentrations, however, the solute may not obey Henry s law in one or both of the solvents (i.e., not form a dilute ideal solution with it). It may, for instance, dimerize or form a regular solution with an appreciable value of b(J) (see section 2.2). Such complications become negligible at very low concentrations, but not necessarily in the saturated solutions. 

According to Flory-Huggins theory, in the limit of x the critical x parameter is 0.5.(H) Below this value the polymer and solvent will be miscible in all proportions. Above this value, the solvent will not dissolve the polymer, but will act only as a swelling solvent. Thus, the pure solvent may not dissolve the polymer even though it is not crosslinked. If x is not , the critical value of x is larger, but the same qualitative arguments regarding mutual solubility of the solvent and polymer hold. Thus, the application of Equation 1 does not require that the pure solvent be able to completely dissolve the polymer, only that the solvent dissolve into the polymer by an amount that can be measured. 

The mutual solubility Of two salts.—Numerous investigations have been made on this subject in the light of the phase rule by H. W. B. Roozeboom 8 and others. C. E. Linebarger also submitted mixtures of two salts to the action of various organic liquids in which one of the salts was insoluble. If both salts passed into soln. in a molecular ratio, it was assumed that a double salt is formed in soln. With a mixture of sodium and mercuric chlorides no double salt was formed with benzene or acetone as solvent, but with acetic ether, a salt, (HgCl2)2NaCl, was formed similarly also with lithium and mercuric chlorides, the salt HgCl2.LiCl was formed but no double salt was observed with potassium and mercuric chlorides in the same solvent. 

The mutual solubilities of components whose molecular sizes are drastically different is the case of the binary polymer-solvent systems, the molecules of the solute... 

Note that if there is some mutual solubility of the two solvents, activity coefficients measured by this method are actually for solvents which are the dilute solutions of one of the solvents in the other. 

The Physicochemical Properties of Solvents and Their Relevance to Electrochemistry. The solvent properties of electrochemical importance include the following protic character (acid-base properties), anodic and cathodic voltage limits (related to redox properties and protic character), mutual solubility of the solute and solvent, and physicochemical properties of the solvent (dielectric constant and polarity, donor or solvating properties, liquid range, viscosity, and spectroscopic properties). Practical factors also enter into the choice and include the availability and cost of the solvent, ease of purification, toxicity, and general ease of handling. 

Leahy [30], van de Waterbeemd [14] and Albery [16] discussed the meaning of the rate constants, koa, kao it is sufficient to state here that the primary process involved is the resolvation of the compound as it moves from the octanol to water environments, that is, the loss of any strongly associated octanol molecules and gain of water. Because of the mutual solubility of these solvents it seems reasonable to say that some solvent molecules may transfer along with the compound (which may not be true for other solvent systems where the mutual solubilities are lower). There may also be molecular conformation changes during this process of transfer, which would also be likely to affect solvation. 

In the first two categories the distribution ratio should be relatively independent of the organic solvent, except for the influence of mutual solubility of the organic solvent with water on the distribution ratio. In the last four the organic solvent may play an active role in the extraction process. 

As a practical matter, there are several limiting features that have restricted the method s usefulness. Among these are association of the third component with either or both solvents, the change in mutual solubility of the solvents which the solute may cause, and ionization in one or both solvents. As a result, reliable quantitative interpretations are possible for only the simplest systems. We shall be content to describe the qualitative aspects of the part which H bonding takes. 

There are inherent complications in partition studies. The presence of at least three components implies many possibilities for interactions. More important is the effect of the mutual solubilities of the two solvent phases. No two solvents are perfectly immiscible, and hence the data always refer to the partition of one component between two binary liquids. The effect of the usually small amount of dissolved solvent can be large. For example, a useful test for distinguishing m/ramolecular and intermolecular H bonding is the determination of the dry and wet melting points. The small amount of water that dissolves in the liquid phase has a pronounced effect on the melting point of intermolecularly H bonded substances. See Section 5.3.4 and Table 5-1V for examples and discussion of this effect. 

In this paper, we describe the apparatus we use to make phase equilibrium measurements on mixtures of conqponents with greatly differing volatilities, putting particular emphasis on recent inqprove-ments over the previous version (6-7). We also describe quantitative measurements of the solubility of methyl oleate in supercritical fluids which can provide a basis for choosing a solvent to separate fatty acids in edible oils. In the following paper (JB.) we explore the utility of cubic equations of state to describe the results of supercritical fluid - liquid phase equilibrium measurements. Some additional experimental results on the mutual solubility of methyl linoleate and carbon dioxide are presented there also. 

The first step is preparation of the solution. Aqueous solutions are prepared by dissolving either soluble salts in solvents (usually water) or metals in acids. For multicomponent systems, the mutual solubility of the various components must be considered. For example, a solution for lead zirconate cannot be prepared from lead nitrate and zirconium sulfate, both of which are soluble in water, because lead sulfate, which is insoluble, will precipitate. A solution of nitrates of both cations is satisfactory. 

Sometimes the mutual solubility of a solvent pair of interest can easily be decreased by adding a third component. For example, it is common practice to add water to a solvent system containing a water-miscible organic solvent (the polar phase) and a hydrophobic organic solvent (the nonpolar phase). A typical example is the solvent system (methanol + water) + dichloromethane. An anhydrous mixture of methanol and dichloromethane is completely miscible, but adding water causes phase splitting. Adjusting the amount of water added to the polar phase also may be used to alter the K values for the extraction, density difference, and interfacial tension. Table 15-5 lists some common examples of solvent systems of this type. These systems are common candidates for fractional extractions. 

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