Nonelectrolytes, solubilities

The assignment of a geometric mean rather than an arithmetic mean or some other function of the two 7 terms is justified primarily on the basis of the successful use of this type of averaging in the theory of nonelectrolyte solubility. Only the London component of y is used since it is the part of y that crosses phase boundaries. 

There is another anomaly to be considered. In nearly all of the nonelectrolyte solubility data that have been subjected to analysis according to eq. [5.5.23] the solute solubility increases as X2, the organic cosolvent concentration, increases, and gA is positive, the physically reasonable result. But in the sucrose-water-ethanol system, the sucrose solubility decreases as Xj increases, and gA is negative. There appears to be no physically reasonable picture of a negative gA value. 

The ion-molecule interaction term, kg, is the one that is most often calculated. Long and McDevit felt that the nonelectrolyte self interaction term could safely be ignored only when the nonelectrolyte solubility was vei low as in the case of the nonpolar electrolytes hydrogen, oxygen and benzene. For the more soluble polar nonelectrolytes, such as ammonia, carbon dioxide and phenol, the self interaction term is of much greater importance and should be determined where data is available. 

Figure A2.5.18. Body-centred cubic arrangement of (3-brass (CiiZn) at low temperature showing two interpenetrating simple cubic superlattices, one all Cu, the other all Zn, and a single lattice of randomly distributed atoms at high temperature. Reproduced from Hildebrand J H and Scott R L 1950 The Solubility of Nonelectrolytes 3rd edn (New York Reinliold) p 342.

A series of studies has been made by Yalkowsky and co-workers. The so-called general solubility equation was used for estimating the solubility of solid nonelectrolytes [17, 18]. The solubility log S (logarithm of solubility expressed as mol/L) was formulated with log P logarithm of octanol/water partition coefficient), and the melting point (MP) as shown in Eq. (11). This equation generally... 

Now interpret phase X as pure solute then Cs and co become the equilibrium solubilities of the solute in solvents S and 0, respectively, and we can apply Eq. (8-58). Again the concentrations should be in the dilute range, but nonideality is not a great problem for nonelectrolytes. For volatile solutes vapor pressure measurements are suitable for this type of determination, and for electrolytes electrode potentials can be used. 

The water-soluble nonelectrolyte X has a molar mass of 410 g/mol A 0.100-g mixture containing this substance and sugar (MM = 342 g/mol) is added to 1.00 g of water to give a solution whose freezing point is —0.500°C. Estimate the mass percent of X in the mixture. 

Sec. 7.4.1), a large range of acid-base properties, and often a better solubility for many materials, electrolytes and nonelectrolytes, better compatibility with electrode materials, and increased chemical stability of the solution. Their drawbacks are lower conductivity, higher costs, flammability, and environmental problems. 

Hildebrand, J.H. and Scott, R.L. Solubility of Nonelectrolytes, Dover, New York, 1964. 

Amidon, G. L, Yalkowski, S. H., Anik, S. T., Valvani, S. C. Solubility of nonelectrolytes in polar solvents V. Estimation of the solubility of aliphatic monofunctional compounds in water... 

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. 

Kamlet, M. J., Doherty, R. M., Abboud, J. L., Abraham, M. H., Taet, R. W., Linear solvation energy relationships 36. Molecular properties governing solubilities of organic nonelectrolytes in water, J. Pharm. Sci. 1986, 75, 338-349. 

Lande, S. S., Baneijee, S. (1981) Predicting aqueous solubility of organic nonelectrolytes from molar volume. Chemosphere 10,751-759. 

Vesala, A. (1974) Thermodynamics of transfer nonelectrolytes from light and heavy water. I. Linear free energy correlations of free energy of transfer with solubility and heat of melting of nonelectrolyte. Acta Chem. Scand. 28A(8), 839-845. 

If the molecular species of the solute present in solution is the same as those present in the crystals (as would be the case for nonelectrolytes), then to a first approximation, the solubility of each enantiomer in a conglomerate is unaffected by the presence of the other enantiomer. If the solutions are not dilute, however, the presence of one enantiomer will influence the activity coefficient of the other and thereby affect its solubility to some extent. Thus, the solubility of a racemic conglomerate is equal to twice that of the individual enantiomer. This relation is known as Meyerhoffer s double solubility rule [147]. If the solubilities are expressed as mole fractions, then the solubility curves are straight lines, parallel to sides SD and SL of the triangle in Fig. 24. 

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