Solubility curve, typical

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. 

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... 

The phase diagrams of two-component surfactant-water systems are typically quite different for nonionic and ionic compounds. As exemplified in Fig. 2.22 there are at low temperatures different liquid crystalline phases while at intermediate temperatures there may be a total mutual solubility of surfactant and water98. At higher temperatures, there is, as already noted, a separation into two phases with a very large two-phase region. One of the phases contains very little surfactant, while the other contains appreciable amounts of both components. The cloud-point curve can be described as a liquid-liquid solubility curve with a lower consolute tempera-... 

Fig. 10.2 shows the changes in the solution composition that occur when a typical Ciment Fondu reacts with water at 20°C, together with the metastable solubility curves for phases in the CaO-Al20,-H20 system. The CaO and AI2O3 concentrations increase, at an approximately constant CaO/ AI2O3 ratio somewhat greater than 1 in the experiment shown, C -ao reached 15 mmol 1 in 3 min and its maximum value of 21 mmol 1 in 1 h. 

The minimum solubility of water In a W/0 mlcroemulslon stabilized by an Ionic surfactant/medium chain length cosurfactant combination depends on the surfactant counter Ion Figure 1 shows a typical solubility curve (19). The reason for this minimum water content Is related to the water of hydration and calculations of the free energy of gaseous water/surfactant aggregates (20) are useful In order to understand the fundamental basis of the phenomenon. 

Gas Solubility. The solubility of natural gas in oil must be re-> ferred to some basis and for this purpose it is customary to use one barrel of stock tank oil. The gas solubility (r) is defined as the number of cubic feet of gas measured at standard conditions which are in solution. in one barrel of stock tank oil at reservoir temperature and pressure. A typical gas solubility curve as a function of pressure is shown in Figure 54 for a saturated crude oil at reservoir temperature. 

Fig. 54. Typical gas-solubility curve as a function of pressure for a saturated crude oil. Gas solubility is expressed in standard cubic feet per stock tank barrel...

Po denotes the ori al reservoir pressure and ro is the ori nal value of the gas solubility. As the pressure is reduced solution gas is liberated and the value of r decreases as shown. If the ori al crude is undersaturated at the initial reservoir temperature and pressure a reduction in pressure to the bubble point or saturation pressure is necessary before gas is evolved from the solution. A typical gas solubility curve for an undersaturated crude is shown in Figure 55. Po and Pj represent the original reservoir pressure and the saturation pressme, respectively. Between Po and P, the gas solubility remains constant at ro but at pressures below Pj gas is evolved and r decreases as shown. 

The solution is supersaturated when the solute concentration exceeds its solubility limit. A solution may maintain its supersatiuation over a concentration range for a certain period without the formation of a secondary phase. This region is called the metastable zone. From the creation of supersaturation to the first appearance of the secondary (solid) phase, the time elapsed is called induction time. As supersaturation increases, the induction time is reduced. When the supersaturation reaches a certain level, the formation of the secondary phase becomes spontaneous as soon as supersamration is generated. This point is defined as the metastable zone width. Figure 2-7 is a typical diagram of the equilibrium solubility curve and the metastable zone curve (Mullin 2001). 

Similar to polymorph materials, nonsolvate materials and solvate exhibit different physical properties and behaviors. Figure 2-17 shows solubility curves of typical nonsolvate and solvate solids as a function of solvent composition and temperature. As shown in the figure, the nonsolvate solid and the solvate solid cross over at composition Aj. Above composition Aj solvate solid has lower solubility (shown as a solid line) than nonsolvate (shown as a dotted line), and is more stable. Similarly, below composition Aj, a nonsolvate sohd has a lower... 

The addition of an antisoivent can be earned out in different ways, as indicated in Fig. 9-1, where the concentration of product is shown on the ordinate and the amount of antisoivent added is shown on the abscissa. A typical equilibrium solubility curve is indicated as A-B-C. (This curve could be concave or linear but is shown as convex for clarity.) The metastable region is indicated as the area between B-C and E-D. From point A to point B, addition of antisoivent will proceed without crystallization because the solution concentration is below the equilibrium solubility. At point B, equilibrium solubility is reached. As the addition of antisoivent continues, supersaturation will develop. The amount of supersaturation that can be developed without nucleation is system specific and will depend on the addition rate, mixing, primaiy and/or secondary nucleation rate, and growth rate, as well as the amount and type of impurities present in solution. 

The slope of the water solubility curves for fuels is about the same, and is constant over the 20—40°C temperature range. Each decrease of 1°C decreases water solubility about 3 ppm. The sensitivity of dissolved water to fuel temperature change is important. For example, the temperature of fuel generally drops as it is pumped into an airport underground hydrant system because subsurface temperatures are about 10 °C lower than typical storage temperatures. This difference produces free water droplets, but these are removed by pumping fuel through a filter-coalescer and hydrophobic barrier before delivery into aircraft. 

The typical forms of Type ] and Type 2 liquid-liquid systems are shown in Figs. 7.2-21 and 7.2-J3. Also illustrated la Fig. 7.2-2 is the effect of temperature on the mutual solubility curve, which may be so pronounced in some cases ns to cause transition from one type of system to the other-... 

FIGURE 7,8-1 Typical rantual solubility curve with points illustrating titration path. 

A typical example of a system in which the components do not combine to form a chemical compound is shown in Figure 4A. Curves AB and BC represent the temperatures at which homogeneous liquid solutions of naphthalene in benzene begin to freeze or to crystallize. The curves also represent, therefore, the temperatures above which mixtures of these two components are completely liquid. The name liquidus is generally given to this type of curve. In aqueous systems of this type one liquidus is the freezing point curve, the other the normal solubility curve. Line DBF represents the temperature at which solid mixtures... 

FIGURE 15.2. The temperature-solubility relationship for typical ionic surfactants illustrating the important characteristics such as the Krafft temperature, the monomer solubility curve, and the limiting monomer concentration at the critical micelle concentration. 

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