Extraction solubility curve

A water extraction/solubility curve for proteins from defatted soybean meal, in the pH range 0.5 to 12, is shown in Fig. 19.15 (Wolf Cowan, 1975). Nondenatured soy protein is most soluble at pH values of 1.5 to 2.5 and 7 to 12 and least soluble at... 

For the system water-acetic acid-MIBK in Fig. 15-11 the raffinate (water) layer is the solubility curve with low concentrations of MIBK, and the extract (MIBK) layer is the solubihty curve with high concentrations of MIBK. The dashed lines are tie lines which connect the two layers in equihbrium as given in Table 15-1. Example 2 describes the right-triangular method of calculating the number of theoretical stages required. 

Emulsification is a stabilizing effect of proteins a lowering of the interfacial tension between immiscible components that allow the formation of a protective layer around oil droplets. The inherent properties of proteins or their molecular conformation, denaturation, aggregation, pH solubility, and susceptibility to divalent cations affect their performance in model and commercial emulsion systems. Emulsion capacity profiles of proteins closely resemble protein solubility curves and thus the factors that influence solubility properties (protein composition and structure, methods and conditions of extraction, processing, and storage) or treatments used to modify protein character also influence emulsifying properties. 

In Figure 2.2-10 a number of P c-sections of a p,q-system at temperatures around the critical temperature of component A are shown. At T=TV the critical point l=g and the / point and g point of the S2hg equilibrium in Figure 2.2-10b coincide in a horizontal point of inflexion. As a result, at higher temperatures (Figure 2.2-10c) the solubility curve of the solid in the supercritical gas still shows a point of inflexion. This results in a sharp increase of the solubility of the solid in the supercritical gas. This effect plays an important role in supercritical extraction processes. 

In Figure 2, the solubility curve of a typically good solvent is shown. In this curve the weight per cent of water in the solvent is plotted vs. temperature. If one chooses an extraction temperature of 38° C., the solvent will dissolve approximately 30% water. If a lower temperature is used and thus a higher water content, the... 

Suggest one or more substances that may already be dissolved in the water on the newly-discovered planet. Test the solubility of the substance and plot solubility curves for the solute in water. Explain why the substance is in the water, and how the substance will affect the life of the settlers. For example, is it safe to drink How can it be removed from the water Once extracted, can it be used for anything else ... 

Actomyosin is generally extracted from fresh rabbit muscles by the use of buffered KCl solutions of an ionic strength of 0.5-0.6 y. (Weber-Edsall solution). The solubility curve of the isolated actomyosin at pH 7 shows an inflection at 0.25 y, above a value of 0.3 u the protein is completely soluble (Hasselbach et al., 1953). At low ionic strengths, actomyosin upon addition of ATP and provided Mg++ ions are present shows superprecipitation. By glycerol extraction, muscle fibers may be prepared to contain essentially only the contractile system. Such fibers will contract normally under the conditions mentioned above for the isolated actomyosin (Weber and Portzehl, 1952). The muscle fibril contains the actomyosin in the insoluble state and in an optimal spatial arrangement (cf. Section IV, A,2). 

Equation (10.20) is often sufficient to model a liquid-liquid extraction system, especially in the early stages of design. Its simplicity is advantageous, but it has no theoretical basis. As a consequence, users should be careful not to extrapolate it to untested compositions. An additional limitation is the fact that Equation (10.20) does not predict the locus of the mutual solubility curve, and, for P > 0, one might be tempted by this equation to extrapolate to conditions that are actually outside the two-phase region (see Figure 10.1). 

The point M is also known as the mix point, and it defines the overall stoichiometric composition of the mixture (i.e., the composition if only a single phase was formed by mixing), while the extract and raffinate compositions E and R are found from constructing a line parallel to the nearest tie lies that also intersects the mix points and the mutual solubility curve. 

The compositions of feeds and solvent mixtures may lie outside the mutual solubility curve but, if upon mixing, the overall stoichiometry is such that the M point falls inside the mutual solubility curve, then two liquid phases will form. Mixtures outside of the mutual solubility curve are only a single phase. Thus, Figure 10.2 indicates that the addition of acetic acid to water increases the solubility of isopropyl ether in both the extract and raffinate phases. Aqueous mixtures containing 50 mass% or more of acetic acid are miscible with isopropyl ether in all proportions. 

During the extraction of otganic species, it may be desirable to modify the solvent. An inert paraffinic compound or mixture may be blended with a suitable modifier (e.g., a species that hydrogen bonds) to enhance the solvent properties. Such properties might include viscosity, density, surface tension, or attraction for the solute. In these cases, the mutual solubility curve may appear as in Fig. 7.2-4 when the solvent mixture is plotted at one vertex. Reasons for solvent blending may include improved solvent selectivity, interiacial tension, reduced solvent phase viscosity, and increased density differences between the two phases. A solvent that forms stable etnulstotte when mixed with the diluent phase, for example, may be suitable for use when it is modified with a suitable inert paraffinic material. 

FIGURE 7.8-5 Liquid-liquid extraction and temperature swing recovery of solvent and product. Regeneration is accomplished by exploiting the temperature dependence of the mutual solubility curve. 

For these reasons, hydrolysis constants simply fitted to solubility data for Th(IV) hydroxide or hydrous oxide or crystalline Th02(cr), e.g., those in [1964NAB/KUD], [1989MOO], are not reliable and usually in strong contradiction to values derived using other methods. Therefore the present review at first selects the hydrolysis constants from studies based on potentiometric and solvent extraction studies. In a second step the selected hydrolysis constants are used to re-evaluate the published solubility data at pH < 5, i.e., to calculate the corresponding solubility constants. The recalculation of the pH-dependent solubility curves provides furthermore a test of the consistency of the selected data set, in particular for the neutral complexes predominant in the neutral and alkaline pH range. 

Alkali-extracted proteins from simflower oil cake (89% proteins, Nx6.25) and wheat gluten (76.5% proteins, Nx5.7) were reacted with n-octanol in the presence of an acid catalyst. Temperature, reaction time and catalyst concentration were varied according to an experimental design to maximize the esterification yield. The latter was determined by alkaline hydrolysis and subsequent analysis by gas chromatography. The hydrolysis of the peptide chain was traced by the determination of the amount of free amino groups in esterified proteins using 2,4,6-trinitrobenzene-sulfonic acid (TNBS) assays. The solubility curves of modified proteins in water as a function of pH were obtained by Kjeldahl analysis to determine the composition of the soluble and insoluble parts. 

Figure 6-53 a shows solubility curves for caffeine in carbon dioxide. The solubility of supercritical gases is a function of pressure and temperature and is influenced by auxiliary components (HPE phase equilibria [6.88-6.90]). Hence, by means of suitable organic components, the solubility may often be increased [6.88]. However, other mainly inorganic components such as nitrogen (Fig. 6-53 b) reduce the loadability and are only of interest with extract separation and to increase the selectivity of separation processes [6.91]. 

In the extraction of undesirable constituents from petroleum fractions, Francis (13) has shown the usefulness of this attack, and has critically reviewed earlier compilations of C.S.T. data. The selective solvent ability of aniline is frequently used as an indication of the effectiveness of such extraction processes, and the so-called aniline point is a measure of this. Aniline point is defined as the temperature at which a mixture of equal volumes of aniline and hydrocarbon separates into two saturated liquid layers. While this is not necessarily the C.S.T. since the solubility curves are not exactly symmetrical, Francis has shown that it will approximate it very closely. A large number of aniline points for different hydrocarbons have been recorded, as well as the C.S.T. s of hydrocarbons with other solvents (13, 36). Francis has used essentially the difference in C.S.T. for a solvent with two types of hydrocarbons as an indication of the selectivity of the solvent in separating the hydrocarbons and has shown the effect on this of chemical structure of the solvent. Similarly, Drew and Hixson (10) and Hixson and Bockelmann (16) have shown the relationship between C.S.T. of propane with various fatty acids and their esters and the selective ability of propane as a solvent in separating them. 

Figure 6.11 also shows that the maximum possible concentration of C in a finished extract will result when sufficient solvent is used to give an extract at Q, the point of maximum abscissa on the solubility curve. 

Purity of Products. The maximum purity of A in the raffinate will be given by an operation in which the nth tie line, corresponding to the last stage, passes through S when extended. This necessarily requires n to be infinity. The absolute maximum purity of C in the solvent-stripped extract will correspond to the case for single contact (tangency of solvent-removal line to the solubility curve for the combined extracts). Since E ordinarily falls within the two-liquid-phase area, this cannot usually be realized, however. 

Consideration of Eqs. (6.99) and (6.101) shows that any extract can be located from any raffinate Rm by extending the line ORm to the S-rich solubility curve. As with all ideal stages, extract Em and raffinate Rm will be in equilibrium and on opposite ends of a tie line. Consequently Ri may be located at the opposite end of a tie line through E% by line ORi extended, Rt, by a tie line through E, etc. The operating point 0 may be located either on the feed or solvent side of the triangle, depending upon the relative amounts of feed and solvent and the slope of the tie lines. 

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