The Effect of Temperature on Solubility

The effect of temperature on the solubility of 5b was investigated in a series of experiments at the same CO2 density (p = 0.75 gcm ). The temperature that generally may affect the solubility of volatile compounds in compressed fluids has only a minor impact on the solubility of the relatively low volatile complex 5b in the investigated range (Fig. 12). At temperatures between 313 and 333 K, approximately the same quantities of 5b are extracted. 

The data in FIGURE 4-3 demonstrates the effect of temperature on the solubility of water in distillate fuel at increasing concentrations. 

P 5.6 Evaluating the Effect of Temperature on the Solubility and/or the Activity Coefficient of a Gaseous Compound (Freon 12) in Freshwater and in Seawater... 

It is necessary to observe, in particular, the effect of temperature on the solubility. At pressures below a given value, which is typical for each binary solute-solvent system, the solubility increases with decreasing temperature. At higher pressures the opposite effect is observed. This characteristic pressure is normally referred to as crossover pressure and it is very important when a process involving solids must be optimized. 

The effect of temperature on the solubility of gases is more predictable than its effect on the solubility of solids. Most gases (helium is the only common exception) become less soluble in water as the temperature increases (Figure 11.7). One consequence of this decreased solubility is that carbonated drinks bubble continuously as they warm up to room temperature after being refrigerated. Soon, they lose so much dissolved C02 that they become "flat." A much more important consequence is the damage to aquatic life that can result from the decrease in concentration of... 

The solubility of a gas is denoted in moles per unit volume of the liquid at a constant pressure and considered as the equilibrium constant between the gas molecules in the solution phase and those in the gas phase. When gases dissolve in water, this is accompanied by the generation of heat, resulting in a decrease of gas solubility. If one replaces the equilibrium constant K in the van t Hoff equation, the effect of temperature on the solubility of a gas, a, can be written as ... 

The density of the melt is 1.89-1.94 gem-3. During electrolysis, along with sodium metal, small quantities of calcium ( 4 wt%) are deposited at the cathode. Calcium has a melting point (804°C) far higher than sodium and a low solubility in sodium (see Table 13) [302], Because of that at the cathode a solid alloy phase Na-Ca is accumulated and this blocks the circulation of the electrolyte in the electrolysis cell and the removal of sodium from the cell. Also this solid alloy sometimes causes short-circuiting in the electrolysis cell. Sodium obtained by electrolysis is cooled to 110-120°C and filtered for the removal of calcium. The effect of temperature on the solubility of calcium in sodium [302] is shown in Table 13. At 110°C the calcium content in sodium is reduced to <0.04%. 

The precipitation is especially enhanced because mostly a saturated KC1 solution is used to decrease the -> junction potential. It should be noted that by changing KC1 for NaCl the potential of the saturated calomel electrode (SCE) will be varied which is due to the different solubilities. In the case of electrodes of the second kind the effect of temperature on the solubility has to be considered, too. It is of importance to prevent to exchange electrolytes between the main and the reference compartments. For instance, a leakage of chloride ions, which is strongly adsorbed at platinum, may influ-... 

Although the composition of an ideal solution can be predicted theoretically, few solutions are ideal, and fugacities and activity coefficients are seldom available for real systems. Hence, in general, too little is known of the direct relationships between solubilities and the specific properties of the solute and the solvent to permit prediction of solubility curves. The characteristics of each system must be determined experimentally. In many cases, it is not even possible to predict the effect of temperature on the solubility values of a given solute-solvent system. 

The effect of temperature on the solubility of PEG(400) In the SCF phase and CO2 in the polymer phase is shown in Figures 6 and 7 respectively. In the SCF phase (Figure 6), a temperature change of 10 dose not affect the solubility of PEG(400) in CO2. This observation suggests that the effects of the vapor pressure of solute and the density of the solvent are to some extent compensating. In the polymer phase (Figure 7), the solubility of CO2 drops with temperature because CO2 is very volatile and evaporates out of the liquid phase very effectively when temperature is increased from 313 to 323 K. 

Solubility varies with temperature. The solubilities of solids usually increase as the temperature rises. For example, more sugar dissolves in hot coffee than in cold coffee. Table 3 shows the effect of temperature on the solubility of sugar. 

Figure 14-6 A graph that illustrates the effect of temperature on the solubilities of some salts. Some compounds exist either as nonhydrated crystalline substances or as hydrated crystals. Hydrated and nonhydrated crystal forms of the same compounds often have different solubilities because of the different total forces of attraction in the solids. The discontinuities in the solubility curves for CaCl2 and Na2S04 are due to transitions between hydrated and nonhydrated crystal forms.

Unlike the aluminosilicates and most other minerals, the carbonates have an exothermic heat of dissolution, which means that their solubilities decrease with increasing temperature. For example, for calcite decreases from 10 at 0°C to 10 at 30°C. The effect of temperature on the solubility products of aragonite, calcite, and ordered dolomite is plotted in Fig. 6.8. The figure shows that between 0 and 90°C solubilities of the carbonates decrease by about 6-fold for aragonite and calcite and 14-fold for dolomite. This decreasing solubility with temperature is magnified by the fact that the solubility of CO2 gas also declines with temperature. Kqq, decreases from 10 " to 10 between 0 and 30°C. 

Till now, there have been many studies on the solubility of nonaqueous solutions of ionic surfactants. On the other hand, information on nonionic surfactant solutions is still scarce. Kon-no et al. [27] studied the effect of temperature on the solubility of a-monoglycerol esters of Qi Q7 fatty acids in benzene. Such solubility behavior has also been observed by Matin and Pink [28] for zinc soaps in various organic solvents. The solubility increases slowly as the temperature is raised. Within a narrow temperature range, the solubility begins to increase very rapidly. The temperature at which the abrupt change in the solubility occurs is called the critical solution temperature (CST). 

Recall that solubility is defined as the maximum amount of a solute that will dissolve in a given quantity of solvent at a specific temperature. Temperature affects the solubility of most substances. In this section we will consider the effects of temperature on the solubility of solids and gases. 

These differences are considerable when compared with the experimental variability (by ANOVA). In other words, the effect of the temperature appears to depend upon the composition of the solvent. The effect of temperature on the solubility is relatively higher in ethanol-water mixtures as the proportion of ethanol increases. ANOVA indicates significant lack-of-fit (sign. = 0.026). We therefore analyse the data using the model of equation 9.10 (coefficients in table 9.15). 

Classical thermodynamics describes the effect of temperature on the solubility of a molecule in solution. If the heat of crystallization, AHcry, and solubility, C, at one temperature (T ) are known, the solubility as a function of temperature can be determined via the van t Hoff equation ... 

PAN/PAT] Pant, G. N., Pathak, D. N., Effect of temperature on the solubility of sparingly soluble phosphates, Fert. Technol., 13, (1976), 296-299. Cited on pages 205, 377. 

Equipment for taking samples for quantitative chemical analyses is by nature complicated because of the alkali metals affinity for oxygen. In addition, the effect of temperature on the solubility of sodium oxide in sodium makes sampling for oxide particularly difficult. This effect is shown in Figure 4. 

The effect of temperature on the solubility of impurities is utilized to maintain purity in liquid metal systems. The process, commonly called cold trapping, uses a cooled pipe section in which oxides can precipitate out and be removed from the main body of the liquid metal. This equipment is shown schematically in Figure 7. 

The effect of temperature on the solubility of a substance in a supercritical fluid changes with pressure. At pressures close to the critical point a temperature rise results in a decrease in the concentration of the solute in the supercritical phase. However, at high pressures, a rise in temperature causes an increase in the solubility because a rise in temperature at constant pressure leads to a decrease in gas density, and at the same time results in an increase in the vapor pressure of the solute. The reduction in gas density, due to an increase in temperature, becomes less at higher pressures than at low pressures. So, the increase in vapor pressure of the solute overcomes the decrease in gas density and leads to a higher concentration in the supercritical phase. 

Fig. 13. The effect of temperature on the solubility in micellar bile acid solution of fatty acid (top), monoglyceride (center), and sodium soap (bottom). The data of Figs. 6, 8, and 10 have been plotted with the coordinates switched and the axes reversed. Fatty acid solubility increases markedly at a temperature close to the melting point of the anhydrous acid. Monoglyceride solubility increases at a temperature close to that of the transition temperature of monoglyceride in water. Thus, for both fatty acids and soap, the temperature at which a marked increase in solubility occurs is determined chiefly by lipolytic product-water interaction. With sodium soaps, the temperature range over which the solubility increases is much broader, and a significant depression is caused by bile acids. For a given acyl radical, the temperature at which solubility increases is lowest for soap, intermediate for monoglyceride, and highest for fatty acid.

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