Solubility curves systems

The third type of system gives a closed solubility curve and therefore possesses both an upper and lower critical solution temperature. The first case of this type to be established was that of nicotine and water the solubility curve is illustrated in Fig. I, 8, 3. The lower and upper consolute temperatures are 60 8° and 208° respectively below the former and above the latter the two liquids are completely miscible. 

It should be noted that the modern view is that all partially miscible liquids should have both a lower and upper critical solution temperature so that all such systems really belong to one class. A closed solubility curve is not obtain in all cases because the physical conditions under normal pressure prevent this. Thus with liquids possessing a lower C.S.T., the critical temperature (the critical point for the liquid vapour system for each component, the maximum temperature at which liquefaction is possible) may be reached before the consolute temperature. Similarly for liquids with an upper C.S.T., one or both of the liquids may freeze before the lower C.S.T. is attained. 

If the system represented by the point D be heated, the solid A will disappear and two partially miscible liquids will remain. The curve ETD is the ordinary solubility curve for two partially miscible liquids (compare Section 1,8, Fig. I, 8, 1). As the temperature rises, the mutual... 

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. 

Case III. As the pressure increases still further, the solubility curve intersects larger liquid-liquid regions until the critical solution pressure of the system has been reached. Above this critical pressure, no vapor phase exists, and the phase diagram consists of only the coexistence curve, as shown in Fig. 28c. In Fig. 28, L, and L2 stand for the two liquid phases and F stands for a fluid phase. 

Frequently, however, the solubility curve has a maximum (as shown by circles in Fig. 2, when plotted as both a function of C2 and [10]. In either case it is possible to optimize solubility by selection of a solvent system with a given value of s that is, once the curve has been established, the optimum water/solvent ratio for another solvent can be calculated from known dielectric constant relationships [11],... 

Supersaturation is the driving force for crystallization and is a prerequisite before a solid phase will appear in a saturated solution. Figure 1. shows the situation for a cooling crystallization. At point 1 the system is under saturated and the concentration of dissolved solute is below the solubility curve defined by Eq 3. As the system cools it becomes saturated at point 2 but remains as a metastable liquid phase until the metastable zone is crossed at point 3, where... 

Figure 5. shows the solubility curves for a monotropic system of two polymorphs and will be used to discuss methods for controlling the polymorphic form of the product. In this instance the thermodynamically stable and thus least soluble polymorph is Form I. 

Where competing polymorphs may occur it is better to have systems where there is a large difference in the relative solubility of the two forms at the point of nucleation. This enables seeding of the crystallizer with the desired form at a temperature between the two solubility curves. A typical seed loading is 1 to 2 % by weight of the product. 

Metastable crystalline phases frequently crystallise to a more stable phase in accordance with Ostwald s rule of stages, and the more common types of phase transformation that occur in crystallising and precipitating systems include those between polymorphs and solvates. Transformations can occur in the solid state, particularly at temperatures near the melting point of the crystalline solid, and because of the intervention of a solvent. A stable phase has a lower solubility than a metastable phase, as indicated by the solubility curves in Figures 15.7a and 15.7/ for enantiotropic and monotropic systems respectively and,... 

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. 

The isothermal solubility curve of mixtures of potassium sulphate and sulphuric acid expresses the composition of the soln. at 25° in equilibrium with the solid phase or phases, when the mol. ratio of K2SO4 and SO3 per 1000 grms. of soln. are plotted as co-ordinates. The ranges of stability in the ternary system K20—S03—H20, are diagrammed in Fig. 51, where the conditions have been studied in the vicinity of the SOs-apex, as far as the formation of KHS207, hut not as far as the well-known potassium pyrosulphate. The meaning of the diagram... 

The homogeneous region of the ternary system is limited by the solubility curve (12). The area with isopiestic measured points is dashed in Figures 3 and 4. 

If such a system undergoes concentration at a given temperature, say 20°, that solid will begin to separate by crystallization which first reaches its saturation value. What will happen as concentration proceeds will depend upon the relation of the solubility curves of the several compounds present in the solution. A few of the simplest cases will be illustrated by diagrams. 

The solubility—temperature curves for the Aa () 1)0 11 () system are given in Figure 5 (Table 9). The solubility curves of the penta- and... 

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. 

Properties of Aqueous Solutions of Arsenic Acid.—The system As,Oj-H20 has been investigated 11 by determining the solubility curves of the (1, 4)- and the (3, 5)-hydrates, and also the curve for the depression of the freezing point of water. The data obtained are given in the following table and are graphically represented in fig. 10. 

The initial step was to study systems with reverse solubility curves to learn the general pattern of the onset of scaling which would be of value for understanding the sea water system. Calcium sulfate, lithium carbonate, sodium sulfate, and calcium hydroxide have reverse solubility curves in water, are readily available, and are soluble to an extent that neither visual observation of scale nor chemical analysis would be a problem. 

Gould et al. [75] studied the solubility relationships of polar, semipolar, and nonpolar drugs in mixed cosolvent systems. As expected, the nonpolar compound showed a log-linear increase in solubility with increasing cosolvent content. The semipolar compound showed parabolic log solubility curves. The polar compound showed a log-linear decrease in solubility with addition of cosolvent. 

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