Solubility of solid compounds

The solubility of solid compounds in water, as well as in other solvents, is determined by the competition between attractions in the solid state between molecules or ions and the solute-solvent attractions that occur in solution. solid that is more attracted to itself than to solvent molecules will not dissolve. A general... 

Fig. 2. Correlation of octanol-water partition coefficient with water solubility for selected aromatic liquids and solids at 25°C log A ow = -0.862 log S +0.710 (r = 0.994, n - 36). The solubilities of solid compounds in the plot are those of their supercooled liquids at 25°C.

Values in parentheses are supercooled liquid solubilities of solid compounds at 25°C, calculated based on their solid solubilities given in the cited references with correction of solid melting. The melting effect of diphenyl oxide is calculated using Eq. (19) based on the fusion data reported by Tsonopoulos and Prausnitz (99). Equation (21) is used for estimation of the melting effect for 2,4,2, 4 -PCB (mp = 34°C) 1,2,3-trichlorobenzene (mp = 53 ) 1,3,5-trichlorobenzene (mp = 63°) 1,2,3,4-tetrachlorobenzene (mp = 47°) and pentachlorobenzene (mp = 86°). 

Precipitation involves the alteration of the ionic equilibrium to produce insoluble precipitates. To remove the sediment, chemical precipitation is allied with solids separation processes such as filtration. Undesirable metal ions and anions are commonly removed from waste streams by converting them to an insoluble form. The process is sometimes preceded by chemical reduction of the metal ions to a form that can be precipitated more easily. Chemical equilibrium can be affected by a variety of means to change the solubility of certain compounds. For e.xample, precipitation can be induced by alkaline agents, sulfides, sulfates, and carbonates. Precipitation with chemicals is a common waste stream treatment process and is effective and reliable. The treatment of sludges is covered next. 

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. 

As we noted in Chapter 4, the solubility of ionic compounds in water varies tremendously from one solid to another. The extent to which solution occurs depends on a balance between two forces, both electrical in nature ... 

A compound whose solubility increases with temperature can be purified by recrystallization. The impure solid is dissolved in a minimum volume of hot water. The hot solution is filtered to remove insoluble impurities, and then the solution is cooled in an ice bath. The solubility of the compound decreases as the temperature drops, causing the substance to precipitate from solution. Soluble impurities usually remain in solution. Purification by recrystallization is not restricted to aqueous solutions. An organic solid can be purified by recrystallization from an appropriate organic solvent. 

The concentrations of species in the solid phase, [HA(s)j, [B(s)j and [XH(s)], by convention are taken as unity. Hence, the quotients in Eqs. (10) reduce to the concentrations of the neutral species in the saturated solution, each called the intrinsic solubility of the compound, Sq. 

Precipitation is a phase-partitioning process whereby solids separate from a solution.34 Dissolution involves movement from the solid or gaseous phase to the aqueous phase. Solids dissolve into ions, whereas gases retain their original chemical structure when dissolved. The solubility of a compound (its tendency to dissolve in water or other solutions) is the main property affecting the precipitation-dissolution process. 

The fungal treatment showed a high efficiency, by completely removing the estrogens (El, E2, and E3), either in biopile or slurry reactors. On the contrary the removal of BFRs in both systems shows differences. Removal after the fungal slurry treatment was rather low compared to the removal obtained in solid-phase system. These results need more research because they are in contradiction with those stated by some researchers that point to the low solubility of these compounds as the limiting factor in its biodegradation. 

The solubility of solids in liquids is an important process for the analyst, who frequently uses dissolution as a primary step in an analysis or uses precipitation as a separation procedure. The dissolution of a solid in a liquid is favoured by the entropy change as explained by the principle of maximum disorder discussed earlier. However it is necessary to supply energy in order to break up the lattice and for ionic solids this may be several hundred kilojoules per mole. Even so many of these compounds are soluble in water. After break up of the lattice the solute species are dispersed within the solvent, requiring further energy and producing some weakening of the solvent-solvent interactions. 

The solubility of a compound can simply be expressed, as above, in terms of grams of compound which will dissolve in 100 grams of water at a specified temperature. A more useful concept is the solubility product, which is defined as follows. If a compound (generically termed MX, where Mn+ is any metal ion and Xn is any anion) is present in a solution in excess of its solubility, then an equilibrium is set up between the dissolved species and the undissolved solid, as follows ... 

New Protocols Based upon Temperature-Dependent Solubilities of Fluorous Compounds and Solid/Liquid Phase Separations... 

Gladysz JA, Tesevic V (2008) Temperature-Controlled Catalyst Recycling New Protocols Based upon Temperature-Dependent Solubilities of Fluorous Compounds and Solid/Liquid Phase Separations. 23 67-89... 

According to Equation (4.5) the ideal solubility of a compound is only dependent upon the heat of fusion, the difference in heat capacity of the solid and supercooled liquid and the melting point of the compound. Since there are no properties of the solvent included in the ideal solubility equation, the solubility of a compound should be the same in all solvents. This equation overlooks all solute-solvent and solvent-solvent interactions. 

The isolation of both specific and nonspecific binding proteins on affinity matrices bearing bioactive compounds hinders the identification of drug cellular targets. While solid-phase elution or the competition methods are conventionally used to distinguish between specific and nonspecific receptor-ligand interactions, these approaches are often severely restricted by low ligand solubility and/or slow kinetic dissociation (8). This low solubility of these compounds are not uncommon, since the hydrophobic properties of these compounds are often vital for their bioactivity and/or membrane permeability. 

We will start our discussion by considering a special case, that is, the situation in which the molecules of a pure compound (gas, liquid, or solid) are partitioned so that its concentration reflects equilibrium between the pure material and aqueous solution. In this case, we refer to the equilibrium concentration (or the saturation concentration) in the aqueous phase as the water solubility or the aqueous solubility of the compound. This concentration will be denoted as Qf. This compound property, which has been determined experimentally for many compounds, tells us the maximum concentration of a given chemical that can be dissolved in pure water at a given temperature. In Section 5.2, we will discuss how the aqueous activity coefficient at saturation, y, , is related to aqueous solubility. We will also examine when we can use yf as the activity coefficient of a compound in diluted aqueous solution, y (which represents a more relevant situation in the environment). 

Divide the saturated solution of -butyl alcohol in water into three approximately equal parts. Treat these respectively with about 2-6 g. of sodium chloride, potassium carbonate and sodium hydroxide, and shake each until the solids have dissolved. Observe the effect of these compounds upon the solubility of n-butanol in water. These results illustrate the phenomenon of salting out of organic compounds, i.e., the decrease of solubility of organic compounds in water when the solution is saturated with an inorganic compound. The alcohol layer which separates is actually a saturated solution of water in -butyl alcohol. 

Using a relationship developed by Yalkowsky and Valvani (1980), a melting point term was included in a LSER for the solubility of solid aromatic compounds, resulting in... 

The reductive dissolution of solid compounds in anaerobic soils, sediments, and waters begins with the reduction of prominent cations within the compounds. Many Fe(III) (oxy)(hydr)oxide compounds are especially susceptible to reductive dissolution. The reduction process converts Fe(III) into more water-soluble Fe(II). The formation of Fe(II) causes the (oxy)(hydr)oxides to decompose in water. In some cases, the Fe(II) rapidly precipitates as new solid compounds, such as siderite (FeCCT) or magnetite (FesCL). 

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