Miscibility of solvents

Ethoxylated mono-, di-, and triesters of phosphoric acid improve the miscibility of solvents, especially butylhydroxypropionate, with water [303]. A mixture of monolauryl phosphate sodium salt and triethylamine in H20 was treated with glycidol at 80°C for 8 h to give 98% lauryl 2,3-dihydroxypropyl phosphate sodium salt [304]. 

This sub-problem considers the mixture properties. Mixture properties can be categorized into two types. Properties such as selectivity, solvent power etc., are based on infinite dilution activity coefficients, which are independent of composition and hence only structural information is needed for their calculation. Properties such as complete or partial miscibility of solvent with another constituent is handled by discritizing the composition range from 0 to 1 into n divisions and verifying the miscibility criterion at those points. The difference between pure component property constraints and mixture property constraints is that the former are linear and the latter are non-linear. Those satisfying the mixture property constraints are further analyzed in sub-problem 4. 

The miscibility of solvent anti-solvent pairs is considered in sub-problem 4M through constraint represented by Eqn.38. Only 6 pairs were found to be mutually miscible with each other. 

Godfrey gave an alternate approach for the prediction of mutual miscibility of solvents (Godfrey, 1972). As a measure of lipophilicity (that is, affinity for oil-like substances) the so-called miscibility numbers (M-numbers, with values between 1 and 31) have been developed. These are serial numbers of 31 classes of organic solvents, ordered empirically by means of simple test tube miscibility experiments and critical solution temperature measurements. There is a close correlation between M-numbers and Hildebrand s 5-values. 

The mutual miscibility of solvents that does not involve water has been reported on an empirical basis by assigning to each solvent a miscibility number, on a scale of standard solvents ranging from 1 for the very hydrophilic glycerol to 31 for the very lipophilic petrolatum. If the miscibility numbers of two solvents differ by < 15 they are probably miscible, whereas if they differ by > 17 they are probably immiscible. Those that have a miscibility number of 16 ought to be miscible with all solvents, hence act as universal solvents. The miscibility numbers are shown in Table 4.6, where, in the cases where two numbers are shown, the first pertains to miscibility with solvents of high lipophilicity and the second to miscibility with solvents of high hydrophilicity (Godfrey 1972). 

The miscibility of solvents with each other must be taken into account when attempting mixed-solvent recrystallizations (see p. 95) the properties of some common recrystallization solvents, which you are likely to encounter in your laboratory work, are shown in Table 13.1. Remember that this is only a general list of solvents further information on solvent properties can be found in standard textbooks such as Harwood et al. (2000, p. 133), Loewenthal (1990, p. 146) and Furniss et al. (1989, p. 137). 

Accepting that the last traces of oil are more difficult to dissolve does not nullify the basic conclusions to be derived from the preceding theories based on simple diffusion with free miscibility of solvent and oil. If free miscibility does not exist in the latter stages of extraction, this means simply that the effective concentration of solute is not the concentration of oil in the solid seed material but a lower concentration that is limited by the solubility of the oil in the solvent. The rate of diffusion will be less than observed in the earlier stages, not because the diffusion coefficient has decreased, but because the oil content of the solid material is no longer a proper measure of its instantaneous content of diffusible material. The diffusion or extraction rate will, for example, still be inversely proportional to the square of the flake thickness. 

The suitability of IGC as a route to interaction thermodynamics using non-volatile stationary phases and selected probe molecules at high dilution has been noted above. Much valuable information on the miscibility of solvent-polymer systems, derived from IGC measurements, continues to be published in the literature. However, equally important is information on the state of interaction among the non-volatile components of complex polymer-containing systems. Such information is an invaluable guide to the formulation of polymer blends and fiber- and particulate-reinforced polymer compounds, and would appear to have at least equal relevance to the properties of high performance, non-... 

In aqueous mixtures, the solvents that are completely miscible with water may be called cosolvents. The complete miscibility of solvents with water depends on their hydrophilic character, expressed as the log P. This is the logarithm of the partition coefficient of the substance considered as a solute between 1-octanol and water. Normally, the solvents with negative log P values are completely miscible with water, and solvents with log P > 1.3 show very limited miscibility with water. Solvents with intermediate values (0 < log P < 1.3) are somewhat miscible with water. 

The solubility parameter concept has been used to correlate many physical phenomena. Miscibility of solvents with polymers, diffusion of solvents within polymers, effects of intermolecular forces on the glass transition temperature and interfacial interactions within copolymer materials would be included, just to mention a few examples. In many cases, meaningful interpretation of results was facilitated with the use of the solubility parameter. 

Miscibility of solvents with the diluent can be an area of concern. It is common to prepare stock standards at higher concentrations, then dilute down to the working standard. Certain solvents may not go completely into solution at these higher concentrations, depending upon the diluent. For example, hexane will not dissolve completely in DMSO at high concentrations. Thus, the stock standard used for hexane will need to be prepared at a lower concentration than that of other solvents. 

Table 3. Miscibility of solvents as a function of the difference in solubility parameters...

Unlike the aqueous surfactant systems, the miscibility of solvent and surfactant increases in surfactant-oil systems with the rise of temperature because... 

Extraction is often used in the fine-chemicals and biotechnology industry. Extraction technology has a number of distinct advantages (selectivity, capacity, robustness and good scalability), but an even longer list of disadvantages expensive solvent recovery, many practical problems such as emulsification and the mutual miscibility of solvent and water, solvent aging by oxidation and other chemical reactions, environmental and safety aspects because of toxicity, explo-sivity and flammability. 

Miscibility of solvent with the antisolvent Solvent must be miscible with the antisolvent. This is an important factor as the rapid precipitation is primarily afforded by rapid mixing of solvent and antisolvent. If organic solvent is partially miscible, precipitation inefficiency may result owing to liquid-phase separation. In addition, the extraction of solvent out of the precipitates will not be efficient in subsequent washing and rinsing cycles. 

Fig. 5. Miscibility of solvents grey squares represent immiscible solvent pairs.

The miscibility of solvents which are transferred from the first to the second dimension is also important when setting up 2D experiments. Incomplete miscibility over the whole composition range will influence the separation in the second dimension and/ or fractions can be trapped in the transfer valve. 

Cohesive energy density and solubility parameters are defined in the section on miscibility of solvents and polymers (Section B). In addition, the applicability of solubility parameters to thermodynamic calculations and their limitations are discussed. Section C contains methods for measuring, calculating and correlating solubility parameters of solvents and polymers. Section D contains... 

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