Solubility semi-empirical approaches

Solvent-polymer compatibility problems are often encountered in industry, such as in the selection of gaskets or hoses for the transportation of solvents. A rough guide exists to aid the selection of solvents for a polymer, or to assess the extent of polymer-liquid interactions. A semi empirical approach has been developed by Hildebrand based on the principle of like dissolves like. The treatment involves relating the enthalpy of mixing to a solubility parameter, S, and its related quantity, 8, called the cohesive energy density. 

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 ... 

It is very important in practice to know what solvents will dissolve a particular polymer. It is often found that certain polymers will become swollen when they are in contact with particular liquids. Also many polymers craze (see Section 5.6.7) when they are subjected to certain liquids. It is possible to go some way towards explaining these phenomena by using a semi-empirical approach which was first suggested by Hildebrand. The main principle that is used is that polymers dissolve in chemically similar solvents and the two parameters that are used are the cohesive energy density C and solubility parameter 8 and these have characteristic values for each polymer and solvent. The cohesive energy density is defined for a liquid by... 

Much effort has been expended on models that can be used to predict the solubility behavior of solutes, with good success being attained using a semi-empirical, group contribution approach [75]. In this system, the contributions made by individual functional groups are summed to yield a composite for the molecule, which implies a summation of free energy contributions from constituents. This method has proven to be useful in the prediction of solubility in water and in water-cosolvent mixtures. In addition to the simplest methodology, a variety of more sophisticated approaches to the prediction of compound solubility have been advanced [68]. 

Such models can be classified in semi-empirical methods (9-13), corresponding states approaches (14-17), pertubation theories (18-20) and equation of state models (21-28), of which the latter were shown to be well able to correlate experimental solubilities in the nearcritical region. 

Greaves AJ, Churchley JH, Hutchings MG, Philhps DAS, Taylor JA (2001) A chemometric approach to understanding the bioelimination of anionic, water-soluble dyes by a biomass using empirical and semi-empirical molecular descriptors. Water Res 35 1225-1239. http // www.doi.org/10.1016/S0043-1354(00)00388-2... 

At the present time it is not possible to predict satisfactorily the solubility of hydrocarbons in liquid oxygen without the use of experimental techniques. Examination of semi-empirical and theoretical approaches is informative, however. The degree of conformity of the hydrocarbon-oxygen system to solubility behavior as defined by Raoult s law will be examined first. 

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