Solubility immiscible pairs

If Z9b(ai) can be equated with P calculated from the entries in Table 2.5, then Z9b(a2) in any other solvent Ab can be estimated from Eq. (2.62). Equation (2.62) is actually a combination of four expressions of the form of Eq. (2.8) (see section 2.2.2), two for water and solvent Ai and two for water and solvent A2, presuming them to be immiscible pairs of liquids. It employs concentrations on the mole fraction scale, and assumes that the systems behave as regular solutions (which they hardly do). This eliminates the use of the solubility parameter 8 of water, which is a troublesome quantity (see Table 2.1). Solvent Ai need not, of course, be 1-octanol for Eq. (2.62) to be employed, and it suggests the general trends encountered if different solvents are used in solvent extraction. 

The small size of lithium frequently confers special properties on its compounds and for this reason the element is sometimes termed anomalous . For example, it is miscible with Na only above 380° and is immiscible with molten K, Rb and Cs, whereas all other pairs of alkali metals are miscible with each other in all proportions. (The ternary alloy containing 12% Na, 47% K and 41% Cs has the lowest known mp, —78°C, of any metallic system.) Li shows many similarities to Mg. This so-called diagonal relationship stems from the similarity in ionic size of the two elements / (Li ) 76pm, / (Mg ) 72pm, compared with / (Na ) 102pm. Thus, as first noted by Arfvedson in establishing lithium as a new element, LiOH and LiiCOs are much less soluble than the corresponding... 

In a fundamental sense, the miscibility, adhesion, interfacial energies, and morphology developed are all thermodynamically interrelated in a complex way to the interaction forces between the polymers. Miscibility of a polymer blend containing two polymers depends on the mutual solubility of the polymeric components. The blend is termed compatible when the solubility parameter of the two components are close to each other and show a single-phase transition temperature. However, most polymer pairs tend to be immiscible due to differences in their viscoelastic properties, surface-tensions, and intermolecular interactions. According to the terminology, the polymer pairs are incompatible and show separate glass transitions. For many purposes, miscibility in polymer blends is neither required nor de-... 

Solubilizing all or part of a sample matrix by contacting with liquids is one of the most widely used sample preparation techniques for gases, vapors, liquids or solids. Additional selectivity is possible by distributing the sample between pairs of immiscible liquids in which the analyte and its matrix have different solubilities. Equipment requirements are generally very simple for solvent extraction techniques. Table 8.2 [4,10], and solutions are easy to manipulate, convenient to inject into chromatographic instruments, and even small volumes of liquids can be measured accurately. Solids can be recovered from volatile solvents by evaporation. Since relatively large solvent volumes are used in most extraction procedures, solvent impurities, contaminants, etc., are always a common cause for concern [65,66]. 

There is a very wide choice of pairs of liquids to act as stationary and mobile phases. It is not necessary for them to be totally immiscible, but a low mutual solubility is desirable. A hydrophilic liquid may be used as the stationary phase with a hydrophobic mobile phase or vice versa. The latter situation is sometimes referred to as a reversed phase system as it was developed later. Water, aqueous buffers and alcohols are suitable mobile phases for the separation of very polar mixtures, whilst hydrocarbons in combination with ethers, esters and chlorinated solvents would be chosen for less polar materials. 

A method similar to the above was proposed recently by Kuhn, which uses a pair of solvents immiscible at a lower temperature but becoming miscible with elevating temperature5. To the present authors this method seems more easily applicable and perhaps more promising than the counter-current distribution, since no special instrumentation is necessary for the former. At any rate, it is obvious that these three methods do not allow fractionation of copolymers only by the composition without interference of the molecular weight, because they all are based on the solubility difference among constituent species. 

Since many metal chelates are strongly coloured they lend themselves to absorptiometric procedures (see Section 10.5) and since formally uncharged chelates are commonly insoluble in water but soluble in an immiscible organic solvent they lend themselves to liquid-liquid extraction and various preconcentration techniques the same is often true of ion-pairs formed from bulky chelated cations (or anions) with suitable anions (or cations). 

Before paired-ion chromatography is discussed, it is illustrative to consider another solubility-based separation which relies on a similar approach. This separation is ion-pair extraction. Ion-pair extraction uses two immiscible liquids (aqueous and organic) often in a separatory funnel. An ionized compound (Aij) that is water soluble can be made to favor solution into the organic phase during an extraction by using a suitable counter ion (Baq) to form a neutral ion pair. Since the ion pair behaves as though it is a nonionic, neutral species, it will prefer to reside in the organic liquid layer, and the entire process can be described by the equation ... 

Whilst the various types of physical mixture have been dealt with above, from complete immiscibility to complete miscibility, two special cases may now be taken, the first of which is that of benzoic acid and water. Here we are essentially concerned with the fact that in the same pair of bodies, immiscibility may be gradually transformed into simple, then mutual solubility, and finally into complete miscibility. In the previous cases the transformation is effected by rise of temperature below the cryohydric temperature ice and benzoic acid are practically without action on one another on fusion of the ice, one-sided solution of the benzoic acid begins later, on fusion of the acid, mutual solubility occurs, changing eventually to complete miscibility. AlexejefTs investigations on this point have settled that benzoic acid, after an increase of solubility with rise of temperature has shown itself, melts at 90°, i.e. 31-4° under the usual melting point This is, therefore,... 

The mole fraction of acetone in the liquid phase is not a strong function of intermolecular interactions for pressures less than approximately 80 bar. For the immiscible systems, the shape of the mole fraction versus pressure curve is characteristic of solubility curves of solids in supercritical solvents Q4), with a minimum around the pure solvent critical point. The effect of changing the intermolecular interactions is in the expected direction the solubility of acetone in the fluid phase is lower (by a factor of 5) for the system with - 0.70 relative to the one with - 0.80. Again, a few percent change in the magnitude of the unlike-pair interactions has a greatly amplified effect on the solubility. 

Solubility differences of this type allow the separation of some quite complex mixtures to be carried out easily and quickly in the laboratory. All that is needed is a pair of immiscible solvents, a separating funnel and an understanding of the effects of pH on the solubility of drugs. An example of this type of separation is shown below. 

Since the nature of anion has a great effect on the properties of IL, there are major differences between ILs with different anions. The introduction of different anions results in an increasing number of alternative ILs with various properties [153], The physical and chemical properties of the ILs can be determined by different ion pairs. IL with l-n-butyl-3-methylimidazolium cation and PF " anion is immiscible with water, whereas IL with same cation and BF anion is water soluble. This example represents the designer solvent property of ILs. By changing the anion, the hydrophobicity, viscosity, density, and solvation of the IL system may be changed [67]. 

Phase-Transfer Catalysis. Since the efficiency of the reaction requires that bisphenoi A be used in the form of water-soluble phenolate anions, while phosgene must be dissolved in a chemically inert and hence water-insoluble solvent, the desired reaction would have to depend on the diffusion rate of the two reactants to the interface between the immiscible solvents. The area of the interface can be increased by vigorous stirring of the two-phase reaction mixture, but a more efficient way to accelerate the process is to induce one of the reactants to migrate into a phase that is not particularly receptive to it. In this example, the sodium phenolate ions are in equilibrium with a phase-transfer catalyst such as tetra-n-butylammonium chloride, and while one of the products of the equilibrium (sodium chloride) remains in the aqueous phase, the other products of the equilibrium (the BPA anion-tetra-rc-butylammonium cation ion pairs) are of sufficiently covalent character to migrate into the nonaqueous phase where they encounter phosgene and the reaction takes place. 

With any given pair of immiscible liquids, two types of emulsions are possible. One is that in which water is the external, and oil, the inteimal phase, known as oil-in-water emulsion, or water outside emulsion (o/w). The other type, with oil as external, and water as the internal phase, is known as water-in-oil emulsion, or oil outside emulsion (W/O). If an emulsion contains 50% water or other aqueous solution, and 50% oil or oil-like substance, it is possible to produce an o/w or a W/O emulsion, which will show the same percent composition but, nevertheless, be two entirely different emulsions. This all depends on the method of emulsification, the emulsifying agent, the soluble materials in the water phase, and the fineness of particles. 

Equation-5, X and Phi denote the molar and volume fiaetion of the components, respectively. Eor two polymers to be miscible, the free energy of mixing must be negative. If the solubility parameters of the polymer pairs are too far apart, the free energy of mixing becomes positive, and compatibilizers are often needed to reduce the interfacial tension between incompatible components in a blend. In industry, both miscible and immiscible polyblends are important materials because they fill (filFerent market needs. 

In liquid-liquid extraction the alkaloids are, after basification, extracted from an aqueous solution with an immiscible organic solvent (e.g., dichloromethane, diethyl ether, ethyl acetate, chloroform), or from an organic solvent with an aqueous acid. With the aid of ion-paring agents (e.g., alkylsulfonic acids), alkaloids can be extracted from an acidic aqueous solution with organic solvents. It should be noted that common ions such as Cl, Br, I, acetate, and trifluoroacetate also result in the formation of ion-pairs which are readily soluble in organic solvents. 

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