Effects of Temperature and Pressure on Solubility

The hypothetical ionic compound AB2 is very soluble in water. AnothCT hypothetical ionic compound, CB2, is only slightly soluble in water. The lattice energies for these compounds are about the same. Provide an explanation for the solubihty difference between these compounds. 

In general, the solubility of a substance depends on temperature. For example, the solubility of ammonium nitrate in 100 mL of water is 118 g atO°C and 811 gatl00°C. Pressure may also have an effect on solubihty, as you will see. 

Most gases become less soluble in water at higher temperatures. The first bubbles that appear when tap water is heated are bubbles of air released as the increasing temperature reduces the solubility of air in water. In contrast, most ionic solids become more soluble in water with rising temperature. 

Solubility of some ionic salts at different temperatures 

The solubilities of the salts NaCI, KN03,and CUSO4 rise with increasing temperature,as is the case with most ionic solids.The solubility of Ce2(Se04)3, however, falls with increasing temperature. 

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Figure 9. Effect of temperature and pressure on solubility (in units of mol/dm ) of adamantane in dense (superoitical) carbon dioxide gas. Data from Ref [36].

It may be added here that Le Chatelier s principle is quite general in nature, and that its applicability is not restricted only to chemical equilibria. It can also be applied to physical equilibria, as for example, to explain qualitatively the effects of temperature and pressure on solubility or the effect of pressure on the melting of a solid. 

Effect of Temperature and Pressure on Solubility Temperature generally has a maiked influence on the solubility of a substance. Pressure can affect the solubility of a gas in a liquid but has little effect if the solute is a solid or liquid. 

Experimental data [36] on the effect of temperature and pressure on the supercritical solubility of adamantane in dense (supercritical) carbon dioxide gas is reported in Fig.9. 

Bassam Z. Shakhashiri, "Effect of Temperature and Pressure on the Solubility of Gases in Liquids," Chemical Demonstrations, A Handbook for Teachers of Chemistry, Vol. 3 (The University of Wisconsin Press, Madison, 1989) pp. 280-282. 

While few things are absolutely insoluble, some solutes are much more soluble in a given solvent than others. The solubility of a solute is the amount of the solute that will dissolve in a given amount of solvent at a given temperature. For example, sodium chloride is quite soluble in water and has a solubility of 39.5 g per 100 mL of water at 25°C. We ll talk later about the effect of temperature on solubility. Oxygen, on the other hand, is not very soluble in water, with a solubility of 42 mg per 100 mL of water at 25°C and a pressure of 1 atm. We ll talk later about the effect of temperature and pressure on the solubility of gases. 

In the studies described here, we examine in more detail the properties of these surfactant aggregates solubilized in supercritical ethane and propane. We present the results of solubility measurements of AOT in pure ethane and propane and of conductance and density measurements of supercritical fluid reverse micelle solutions. The effect of temperature and pressure on phase behavior of ternary mixtures consisting of AOT/water/supercritical ethane or propane are also examined. We report that the phase behavior of these systems is dependent on fluid pressure in contrast to liquid systems where similar changes in pressure have little or no effect. We have focused our attention on the reverse micelle region where mixtures containing 80 to 100% by weight alkane were examined. The new evidence supports and extends our initial findings related to reverse micelle structures in supercritical fluids. We report properties of these systems which may be important in the field of enhanced oil recovery. 

Because of difficulties in precisely calculating the total ion activity coefficient (y) of calcium and carbonate ions in seawater, and the effects of temperature and pressure on the activity coefficients, a semi-empirical approach has been generally adopted by chemical oceanographers for calculating saturation states. This approach utilizes the apparent (stoichiometric) solubility constant (K ), which is the equilibrium ion molal (m) product. Values of K are directly determined in seawater (as ionic medium) at various temperatures, pressures and salinities. In this approach ... 

Andrio et al. reported the effect of temperature and pressure on the permeability, diffusion and solubility coefficients of N2, O2 and CO2 in NR reinforced with different amounts of cellulose. Rubber compounds were prepared by adding cellulose II, as 10% cellulose xanthate aqueous solution, to NR latex under stirring. Analysis of the results obtained by these authors... 

Besides the effect of temperature and pressure, the mechanical pressure exerted on the solid phase, and its state of division, influence (although only to a slight extent) its solubility in the liquid. Thus, if a moist precipitate is exposed to pressure in a filter-press, it usually aggregates together, and Hulett (1901) showed that the effect of division (i.e., of surface tension) becomes... 

Although there were some differences on the effects of temperature and pressure according to each particular compound, the free bases of hyoscyamine (1), scopolamine (2), and pseudoephedrine (6) were all found to be highly soluble in supercritical CO,. However, the hydrochloride salts of these compounds were scarcely extracted by pure CO, under any conditions employed. These results were consistent with preliminary evidence indicating that these alkaloids are not extracted from plant materials by pure CO,. This means that the alkaloids in living cells in the plant are not in the form of their free bases but rather as water-soluble salts in the cell vacuole [40]. Therefore, it was necessary to develop a procedure to enhance the solubilities of alkaloidal salts in CO,. 

Before proceeding to develop a method for SFE of a natural product, the feasibility has to be ascertained. To determine the feasibility of SFE as a potential extraction technique, the solubility of the target compound in supercritical carbon dioxide or other supercritical fluid of choice (e.g., butane) has to be determined. If the compound is poorly soluble in supercritical fluid(s), SFE is probably not the preferred extraction method. Solubility experiments to determine the effect of temperature and pressure (which in turn control the density) on the solubility of the target compound in the supercritical fluid have to be performed. 

In this paper solubility measurements of synthetic and natural dyestuffs are presented using VIS-spectroscopy. The investigations concentrate on two different methods. I. P-carotene was measured as a function of temperature and pressure in near- and supercritical C02 (289 to 309 K, 10 to 160 MPa) and CC1F3 (297 to 326 K, 12 to 180 MPa), respectively, using a static method. II. Additionally, the solubilities of l,4-bis-(n-alkylamino)-9,10-anthraquinones (with n-alkyl = butyl, octyl) were determined with a dynamic method in temperature and pressure ranges from 310 to 340 K and 8 to 20 MPa, respectively this method permits a continuous purification from better soluble impurities as well as the measurement of solubilities at the same time. For both anthraquinone dyestuffs intersection points of the solubility isotherms were found in the plot of concentration versus pressure. This behavior can be explained by a density effect. 

Solubility data of the dyestuffs are of interest for the optimization of this particular dyeing technique. Therefore an apparatus was developed for the determination of the solubilities in supercritical solvents at temperatures from 250 to 500 K and pressures up to 250 MPa according to the static analytical method [6, 7]. In particular, investigations on the solubility of some selected anthraquinone dyes in supercritical C02 and N20 and more recently of P-carotene in supercritical C02 and CC1F, were performed as a function of temperature and pressure (see section 4.). For the l,4-bis-(n-alkylamino)-9,10-anthraquinones the alkyl chains were systematically varied in the homologous series in order to study the effects of molecular size and polarity on the solubility phenomena [6-10]. 

As discussed in Chapters 4 and 5, CBPC formation is governed by the oxide solubility. The solubility, in turn, is related to the Gibbs free energy, which is a function of temperature and pressure. As a result, the CBS formulation depends on the downhole temperature and pressure. The effect of the temperature on the solubility has already been discussed in Section 6.4. The pressure effect can be assessed in a similar manner, but as we shall see, it is negligibly small and can be ignored for all practical purposes. 

In this chapter, we present results of the testing of a broad spectrum of polymers in carbon dioxide over a range of temperatures and pressures and evaluation of the effect of the high pressure carbon dioxide on the chemical/physical properties of materials tested. The testing was performed in a static manner with four controlled variables, namely temperature, pressure, treatment time and decompression time. The evaluation of the interaction of high pressure carbon dioxide with polymers included sorption and swelling behavior, solubility issue, plasticization and crystallization, and mechanical properties. The results of these evaluations are discussed in three sections Sorption, Swelling and Dissolution of Carbon Dioxide in Polymers at Elevated Pressure, Thermal Properties, and Mechanical Properties. ... 

We have studied the effect of the temperature and pressure on the conformations and dynamics of a soluble, globular BPTI protein. 

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