Cohesive density

A nonpolar neutral species in a polar medium such as water experiences interfacial tension. Solvophobic theory is a general statement of hydrophobic theory, which has been developed to explain the tendency of neutral organic species to flee the water phase. It has been reported that the solution of nonelectrolytes in water is attended by a net decrease in entropy [65,158]. This has been attributed to an increased structuring of water molecules in the vicinity of the solute. The process may be conceptually rationalized by considering that a solute must occupy space in a cohesive medium. The solute must create a cavity in the water milieu and then occupy that cavity [19,65,158]. The very high cohesive density of water creates considerable interfacial tension in the... 

Hildebrand (1949) designated nonideal solutions as regular if there was sufLcient thermal agitation to overcome the segregating effect of unequal cohesive densities between the solute and... 

The specific surface energy of a polymer can be estimated by means of an additive quantity, the Parachor. Alternatively, it maybe calculated from the molar cohesive density (which is also additive). Rules are given for the estimation of the interfacial tension and the contact angle of a liquid on a solid. 

A quantity that is derived from the cohesion energy is known as the specific cohesion or the cohesion density, EJV, where V is the molar volume. The solubility parameter, S, is the square root of the specific cohesion, and it is expressed by the equation... 

The molecular interaction is characterized by the specific cohesion or cohesion density UjV, where V is the molecular volume (Table 33). Another closely related quantity is the so-called internal pressure of a liquid. 

Rapid predictive and experimental techniques for screening extractive distillation solvents are reviewed. In preparing a list of potential solvents the method of Scheibel is recommended for non-hydrocarbon systems for hydrocarbon systems solvents of high polar cohesive density should be considered. For screening the potential solvents the method of Pierotti, Deal, and Derr is recommended. If it is not applicable, the method of Helpinstill and Van Winkle should be considered next. Finally, reliable screening is accomplished through a simple, rapid technique recently developed that uses gas-liquid chromatography. 

Figure 2. Variation of selectivity with solvent s polar cohesive density system hexane (l -benzene (2) at 25°C (12)...

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