Parachor temperature dependence

Since the parachor (Ps) is practically independent of temperature, Eq. (8.5) can also be used to calculate the temperature-dependence of the surface tension (y). 

The parachor is related to physico-chemical properties depending on the molecule volume, that is, —> boiling point. It is essentially constant over wide ranges of temperature. 

Absence of association in the oligomer is indicated by the fact that the values of the parachor (calculated from the experimental data and from the summation of atoms, bonds, and groups in a molecule according to the additive rule) coincide and hardly depend on the temperature. A similar picture was observed for the siuface molar entropy. This indicates that the extent of macromolecular association does not change within the studied range of temperatures. The entropy of formation of the surface per cm ... 

Molar volume is not a suitable parameter, for two reasons (i) Molar volumes vary with temperature and must be compared at temperatures and pressures proportional to critical values, (ii) Calculations of molar volumes are highly dependent on molecular structure, due to differences in intermolecular attraction. The parachor, [P], overcomes these difficulties by using surface tension, a property dependent on intermolecular attraction. Parachor is defined by Equation (34). M is molecular weight, y surface tension and D and d are densities of liquid and vapour respectively. SinceD>d, Equation(35)follows. 

Over wide ranges of temperatures, parachor values for pure substances are nearly constant, but for solutions they depend on concentration of solutes. Using surface tensions and densities from 10 to 50 °C temperature range, which were determined in the Silesian University, the parachor values for aqueous solutions of citric acid can be expressed by... 

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