Solubility salts effects

In the isolation of organic compounds from aqueous solutions, use is frequently made of the fact that the solubility of many organic substances in water is considerably decreased by the presence of dissolved inorganic salts (sodium chloride, calcium chloride, ammonium sulphate, etc.). This is the so-called salting-out effect. A further advantage is that the solubility of partially miscible organic solvents, such as ether, is considerably less in the salt solution, thus reducing the loss of solvent in extractions. 

Reactions involving organic substances have some special features. Many of these substances are poorly soluble in aqueous solutions. Sometimes their solubilities can be raised by adding to the solution the salts of aromatic sulfonic acids with cations of the type [NHJ or alkali metal ions. These salts have a salting-in effect on poorly soluble organic substances. In many cases solutions in mixed or nonaque-ous solvents (e.g., methanol) are used. Suspensions of the organic substances in aqueous solutions are also useful for electrosynthesis. 

Similarly, concepts of solvation must be employed in the measurement of equilibrium quantities to explain some anomalies, primarily the salting-out effect. Addition of an electrolyte to an aqueous solution of a non-electrolyte results in transfer of part of the water to the hydration sheath of the ion, decreasing the amount of free solvent, and the solubility of the nonelectrolyte decreases. This effect depends, however, on the electrolyte selected. In addition, the activity coefficient values (obtained, for example, by measuring the freezing point) can indicate the magnitude of hydration numbers. Exchange of the open structure of pure water for the more compact structure of the hydration sheath is the cause of lower compressibility of the electrolyte solution compared to pure water and of lower apparent volumes of the ions in solution in comparison with their effective volumes in the crystals. Again, this method yields the overall hydration number. 

The salting-in effect may be used to increase the solubility of a drug substance through the formation of associated ion pairs, most commonly making use of anionic countering (hydrochloride being the most popular). Detailed reviews of pharmaceutical salts have been published, which contain extensive tables of anions and cations acceptable for pharmaceutical use [44,47]. These articles also describe useful processes for the selection of the most desirable salt... 

Soy proteins are used extensively in meat and meat products by the military, the school lunch program and consumers to save money. Their ultimate acceptability is equally dependent upon the nutritional, chemical, sensory and shelf life changes which occur when they are added. Soy proteins in meat products such as ground beef inhibit rancidity, improve tenderness, increase moisture retention, decrease cooking shrink, fat dispersion during cooking and have no important effect on microbiological condition. Concomittantly, inordinate amounts of added soy protein may cause the meat product to be too soft, exhibit an undesirable flavor and may lead to a decreased PER and a deficiency in B-vitamins and trace minerals. In emulsified meat products, soy protein effectively binds water but does not emulsify fat as well as salt soluble muscle protein. Prudent incorporation of plant proteins can result in an improvement of the quality of the meat product with inconsequential adverse effects. 

It is interesting to note that the molecule-ion interaction contribution in equation (5) is consistent with the well-known Setschenow equation. The Setschenow equation is used to represent the salting-out effect of salts on molecular nonelectrolyte solutes, when the solubilities of the latter are small (Gordon, (15)). The Setschenow equation is... 

The addition of an amino acid to mixed solvents at selected temperatures can be a means to compensate even partially for the decrease of dielectric constant due to the solvent addition. Limitations are imposed by the solubility of the amino acid in such mixtures for instance, there is a salting-out effect in methanol-water 50 50 at 25°C when the concentration of glycine is about 0.5 Af (8 20). 

Since [Fe(lll)]jojaj [Fe " ], the formation of ion pairs and complexes is greatly enhancing the equilibrium solubility of ferrihydrite. This is called the salting-in effect and illustrates why mineral solubility calculations in seawater must take ion speciation into consideration. 

Washing and Cleaning Action. The properties of alkyl ether sulfates, due to the good solubility and the special hydrophilic/hydrophobic properties of the molecule, are of particular practical interest. From the investigations described in sections 2 and 3, it can be concluded that, in addition to the decrease in the Krafft Point, favorable properties for practical applications can be expected as a result of the inclusion of the oxyethylene groups into the hydrophobic part of the molecule. As is true for other anionic surfactants, the electrical double layer will be compressed by the addition of multivalent cations. By this means, the adsorption at the interface is increased, the surface activity is raised, and, furthermore, the critical micelle concentration decreased. In the case of the alkyl ether sulfates, however these effects can be obtained without encountering undesirable salting out effects. 

Effects of electrolytes on the solubility of organic compounds in aqueous solutions were established empirically more than 100 years ago by Setschenow (1889). He found that the presence of dissolved inorganic salts in an aqueous solution decreases the aqueous solubility of nonpolar and weak polar organic compounds. This effect, known as the salting-out effect, is expressed by the empirical Setschenow formula... 

The salting-out effect (see Sect. 6.5) may lead to lower solubility of organic or organo-metaUic contaminants in saline waters compared to those obtained in pure water. The solubility decreases with an increase of salt concentration in water. An extreme example may be found in Sorensen et al. (2002), who examined solubility of... 

Fig. 8.24 Decrease in kerosene solubility in a NaCl aqueous solutions of various concentration as result of the salting-out effect (Dror et al. 2000a). and denote concentrations at initial...

Although BMI-BF4 is soluble in water at room temperature, the presence of potassium chloride (KCI) gives a salting-out effect, affording two phases. By adding more water a homogeneous colorless solution can be obtained. 

It should be noted, however, that water solubility is influenced by various environmental factors not included in this equation, the most obvious being temperature and pressure. Water solubility also tends to decrease with increasing salinity via a salting-out effect. This equation is therefore not particularly useful for high-melting nonionic solids. 

According to the ionic hypothesis, if the solubility product [Li]2[C0"3] is not altered, the solubility can be increased by the union of one or other of the ions of the carbonate forming complexes with the added salt. This effect is not very marked with potassium or sodium chloride or nitrate. The marked increase in the solubility with sodium and potassium sulphates is due to the formation of lithium sulphate, but with the ammonium salts soluble complexes like Li(NH3) and NH2C00 may be formed just as is the case with magnesium carbonate in the presence of ammonium salts. 

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