Solubility of gases in solids

The solubilities of gases in solid metals are much lower than liquid metals. Figure 10.18 shows the solubility of hydrogen in copper and copper-aluminum alloys. Because of the lower solubility in the solid, gas bubbles are released at the liquid-solid interface as the metal freezes. With long dendrites the gas bubbles are trapped and the result is gas porosity. 

As already noted, the origin of planetary noble gases remains mysterious. Equilibrium solubility of gases in solids yields concentrations far too low adsorption may... 

Polymerization frequently is performed in gas-phase reactors at intermediate pressures. The role of heterogeneous catalysts and the interaction between reaction kinetics and mass transfer can only be understood if sorption effects, solubilities of gases in solids, volume changes, and diffusivities at reactor conditions are known. 

Because of the wide field of industrial applications, the need exists to develop simple and reliable techniques for the characterization of solids behavior in the presence of dense gases. From our experience we know that information on sorption equilibria or solubilities of gases in solids, on mass-transfer kinetics, and on volume changes are the most relevant in process design. We have therefore developed experimental methods to obtain these properties through laboratory testwork. 

The solubility of gases in solids imposes a serious limitation on the thermo-gravimetric method, as discussed by Guiochon (50). It is difficult to eliminate or even measure and is generally unknown. This was shown by the heating of solid ammonium nitrate initially containing I % nitric acid at 200°C for 3 h. At the end of this period, the sample contained 0.6% nitric acid. This acid has no catalytic effect on the decomposition of the sample, which gives no nitric acid under these conditions, so that only the slowness of its evaporation... 

A wide variety of physical properties are important in the evaluation of ionic liquids (ILs) for potential use in industrial processes. These include pure component properties such as density, isothermal compressibility, volume expansivity, viscosity, heat capacity, and thermal conductivity. However, a wide variety of mixture properties are also important, the most vital of these being the phase behavior of ionic liquids with other compounds. Knowledge of the phase behavior of ionic liquids with gases, liquids, and solids is necessary to assess the feasibility of their use for reactions, separations, and materials processing. Even from the limited data currently available, it is clear that the cation, the substituents on the cation, and the anion can be chosen to enhance or suppress the solubility of ionic liquids in other compounds and the solubility of other compounds in the ionic liquids. For instance, an increase in allcyl chain length decreases the mutual solubility with water, but some anions ([BFJ , for example) can increase mutual solubility with water (compared to [PFg] , for instance) [1-3]. While many mixture properties and many types of phase behavior are important, we focus here on the solubility of gases in room temperature IFs. 

Near room temperature most gases become less soluble in water as the temperature is raised. The lower solubility of gases in warm water is responsible for the tiny bubbles that appear when cool water from the faucet is left to stand in a warm room. The bubbles consist of air that dissolved when the water was cooler it comes out of solution as the temperature rises. In contrast, most ionic and molecular solids are more soluble in warm water than in cold (Fig. 8.22). We make use of this characteristic in the laboratory to dissolve a substance and to grow crystals by letting a saturated solution cool slowly. However, a few solids containing ions that are extensively hydrated in water, such as lithium carbonate, are less soluble at high temperatures than at low. A small number of compounds show a mixed behavior. For example, the solubility of sodium sulfate decahydrate increases up to 32°C but then decreases as the temperature is raised further. 

The solubility of most solids increases with increasing temperature. However, the solubility of gases in liquids decreases with increasing temperature. For example, if you open a cold bottle of soda and a warm bottle of soda, more gas is released by the warm soda. This is the basis of thermal pollution, in which the solubility of oxygen in stream or lake water is decreased if the water is polluted by heat. 

In this chapter, you learned about solutions. A solution is a homogeneous mixture composed of a solvent and one or more solutes. Solutions may be unsaturated, saturated, or supersaturated. Solution concentration units include percentage, molarity, molality, and mole fraction. The solubility of solids in liquids normally increases with increasing temperature, but the reverse is true of gases dissolving in liquids. The solubility of gases in liquids increases with increasing pressure. 

The focus in this chapter has primarily been on solid solutes in liquid solvents. The solubility of gases in water and other liquids... 

Another factor that differentiates the solubility of gases from solids and liquids is the effect of pressure. The effect of pressure on gas solubility was studied extensively by a contemporary and close associate of John Dalton named William Henry (1775-1836). Henry s Law states that the solubility of a gas is directly proportional to the partial pressure of that gas over the solution. Stated mathematically, Henry s Law is c = kP, where c is the concentration of the dissolved gas in moles per liter, k is Henry s law constant for the solution, and P is the partial pressure of the gas above the solution. Henry s Law is demonstrated every time a carbonated beverage is opened. During the carbonation process, carbon dioxide is dis-... 

In this chapter, we have so far discussed the adsorption of gases in solids. This section gives a brief description of the adsorption process from liquid solutions. This adsorption process has its own peculiarities compared with gas-solid adsorption, since the fundamental principles and methodology are different in almost all aspects [2,4,5], In the simplest situation, that is, a binary solution, the composition of the adsorbed phase is generally unknown. Additionally, adsorption in the liquid phase is affected by numerous factors, such as pH, type of adsorbent, solubility of adsorbate in the solvent, temperature, as well as adsorptive concentration [2,4,5,84], This is why, independently of the industrial importance of adsorption from liquid phase, it is less studied than adsorption from the gas phase [2],... 

For the ideal solubilities of gases in liquids, a similar approach to that taken in Section 3.1 for the ideal solubilities of solids in liquids can be used and thus, Equation (3.69), analogous to Equation (3.8), is obtained ... 

Increases in pressure increase the solubility of gaseous solutes, but have little effect on solid solutes. Similarly, decreases in pressure decrease the solubility of gases in liquids and have little effect on solid solutes. 

The correct answer is (B). Gases are most soluble in liquids at low temperature. This is unlike most solids, which become less soluble at lower temperatures. In addition, high external pressures increase the solubility of gases in liquids. For solids, pressure has a negligible effect. 

Changing the pressure has no appreciable effect on the solubilities of either solids or liquids in liquids. The solubilities of gases in all solvents increase, however, as the partial pressures of the gases increase (Figure 14-7). Carbonated water is a saturated solution of carbon dioxide in water under pressure. When a can or bottle of a carbonated beverage is opened, the pressure on the surface of the beverage is reduced to atmospheric pressure, and much of the CO2 bubbles out of solution. If the container is left open, the beverage becomes flat because the released CO2 escapes. 

Increases in pressure increase the solubility of gaseous solutes, but have little effect on solid solutes. Similarly, decreases in pressure decrease the solubility of gases in liquids and have little effect on solid solutes. There are four main coUigative properties, or properties of a solvent that are affected by the presence of a solute vapor-pressure reduction, boiling-point elevation, freezing-point depression, and osmotic pressure. 

These three approaches have found widespread application to a large variety of systems and equilibria types ranging from vapor-liquid equilibria for binary and multicomponent polymer solutions, blends, and copolymers, liquid-liquid equilibria for polymer solutions and blends, solid-liquid-liquid equilibria, and solubility of gases in polymers, to mention only a few. In some cases, the results are purely predictive in others interaction parameters are required and the models are capable of correlating (describing) the experimental information. In Section 16.7, we attempt to summarize and comparatively discuss the performance of these three approaches. We attempt there, for reasons of completion, to discuss the performance of a few other (mostly) predictive models such as the group-contribution lattice fluid and the group-contribution Flory equations of state, which are not extensively discussed separately. 

Increasing temperature usually iucreases the solubility of solid and liquid substances and decreases the solubility of gases in water. 

The study of vapor-liquid equilibria (Sec 10.1) of the solubility of gases in liquids (Sec. 11.1), and of the solubility of solids in liquids (Sec. 12.1), all involve nonsimple, mixtures. To see why this occurs, consider the criterion for vapor-liquid equilibrium ... 

The solubility of gases in liquids is increased and that of solids is usually decreased by raising the pressure. Therefore, the solid solute of a saturated solution may precipitate during the generation of pressure and is no longer accessible for the reaction. The viscosity of liquid increases approximately twice every kilobar. This effect is particularly important for reactions containing diffusion-controlled steps. Finally, the compressibility of liquids is usually small compared to that of... 

This technique takes advantage of the fact that the solubility of gases in HCs (either liquid or solid) can lower significantly the melting temperature of the HC. 

It is possible to measure the partial pressure of any gas in a mixture directly if there is a membrane that is permeable to that gas alone for example, palladium is permeable to hydrogen and certain types of glass are permeable to helium. The fact that at present only a few such membranes are known does not destroy the physical reality of the concept of partial pressure. Later it will be shown that in chemical equilibria involving gases and in physical equilibria such as solubility of gases in liquids and solids, it is the partial pressures of the gases in the mixture that are significant (further confirmation of the physical content of the concept). 

The solubility of gases in ice can be described by the same principles governing solubility of gases in liquids. Solubility of gases in liquids or ice occurs to establish equilibrium, where the affinities of the gas to reside in the gaseous, liquid, and solid state are balanced. The solubility process can be described by two principle mechanisms ... 

Conversions of up to about 80% oxetane were observed (Table 15), and quantum yields in the solid phase were independent of temperature between 23 and 65°C and relativey low (0.012). No change was observed at the glass transition temperature (Tg = 40°C). Such a result agrees with a number of studies of diffusion coefficients and equilibrium solubilities of gases in amoiphous polymer, which show that there is often no abrupt change in diffusivity or solubility at Tg for gases that are small in relation to the polymer repeating unit. 

In contrast to solid solutes, the solubility of gases in water decreases with increasing temperature ( FIGURE 13.19). If a glass of cold tap water is warmed, you can see bubbles on the inside of the glass because some of the dissolved air comes out of solution. 

What is the effect of pressure on the solubility of gases in liquids of solids in liquids ... 

The statistical mechanical theory of the vapor pressure isotope effect can be applied to the interpretation of isotope effects on other phase equilibria (e.g., solid-liquid, liquid-liquid miscibility, solubility of gases in liquids, etc.). 

Permeability equations for diffusion in solids. In many cases the experimental data for diffusion of gases in solids are not given as diffusivities and solubilities but. as permeabilities, Pm, in m of solute gas A at STP (0°C and 1 atm press) diffusing per second per m cross-sectional area through a solid 1 m thick under a pressure difference of 1 atm pressure. This can be related to Pick s equation (6.5-2) as follows. 

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