Cohesive energy density, definition

Thermodynamic Properties The variation in solvent strength of a supercritical fluid From gaslike to hquidlike values may oe described qualitatively in terms of the density, p, or the solubihty parameter, 6 (square root of the cohesive energy density). It is shown For gaseous, hquid, and SCF CO9 as a function of pressure in Fig. 22-17 according to the rigorous thermodynamic definition ... 

In this expression, he divides the number of calories generated on the lipophile side of the surfactant by the number of calories generated by the hydrophile side of the surfactant. The amount of calories reflects or implies a proportional amount of swelling of the hydrophile and the lipophile, i.e., the greater number of calories on the lipophile side, the more tendency there is to form an oil in water type of emulsion. This definition of the C.E.R. (or Cohesive Energy Ratio) parameter leads to a direct expression which ties HLB to the Cohesive Energy Density parameter directly. The expression is ... 

Often referred to as the solvent cohesive energy density, the Hildebrand solubility parameter is considered to be a measure of the solvent contribution to the cavity term, and is used as a correction factor in the - solvatochromic equation. It is related to the general definition of London cohesive energy between two interacting species ... 

It is worth pointing out that, with the above definitions, -E in Equation 2.36 is simply the cohesive energy of the system. The cohesive energy density, then, is given by... 

With these definitions we may write for the cohesive energy density of the hydrogen-bonded system ... 

Pressure effects on surfactant systems containing conventional liquid alkanes have not often been studied because of the very low compressibility of liquids. Conflicting results have been reported [38-40]. It is likely that the changes in cohesive energy density (solubility parameter) of the phases over the pressure ranges used were too low to produce definitive trends in phase behavior. The solubility parameter of compressed liquid propane, however, is moderately adjustable with pressure, and therefore a propane-brine-AOT system could be expected to show pressure-driven phase transitions [20,22,41]. 

The solubility parameter is defined as a measure of cohesive energy density or the internal pressure that is exerted by the molecules within a solution. It is obtained from the following definition ... 

General Characteristics of Starch. The properties of starch are closely related to the existence of hydrogen bonds between the two strands of the double helix forming the crystalline zones. Interchain interactions ensure most of the cohesive properties of the system. However, due to the molecular structure, certain polymer-polymer interactions cannot be established and the cohesive energy density is definitely lower than that of native cellulose. 

Table 24.3 compares the estimated ratios of the defined surface energy density, surface atomic cohesive energy, and the traditionally defined surface energy. Results show that the (y s) is always higher and the (yfj) is always lower than the bulk values. Therefore, it is not surprising that measurements show inconsistent values of surface energy because of the definitions. 

Values of c are calculated from experimentally determined enthalpies (heats) of vapourization of the solvent to a gas of zero pressure, AH, at a temperature T, as well as from the molecular mass M, the density of the solvent g, and the gas constant, R. The cohesive pressure characterizes the amount of energy needed to separate molecules of a Hquid and is therefore a measure of the attractive forces between solvent molecules. The cohesive pressure c is related to the internal pressure n, because cohesion is related to the pressure within a liquid cf. Eq. (3-6) in Section 3.2 for the precise definition of n. ... 

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