Enthalpy corresponding states correlation

A cubic equation of state model cannot predict all the properties with equal accuracy. Usually there is a non-negligible error in estimating liquid volume, which produces also errors in computing enthalpies, frequently underestimated. More accurate methods for enthalpy and entropy are based on corresponding states correlation (Lee-Kesler). 

The Kesler-Lee correlations for liquid and vapour phase heat capacities of petroleum fluids are used for estimating the respective enthalpies at temperatures of interest. The Lee-Kesler corresponding-states method is used for obtaining estimates of the heats of vaporization and for developing the saturation envelope enthalpies. This method uses the Curl and Pitzer approach and calculates various thermodynamic properties by representing the compressibility factor of any fluid in terms of a simple fluid and a reference fluid as follows ... 

Trens et al. [11], have correlated the intersection of the desorption branch with the adsorption branch at the low pressure (referred to as the reversible pore filling or rpf ) with thermodynamic properties. Specifically, it seems to follow the Clausius-Clapeyron equation and follows that relationship expected from corresponding states relationship. This indicates that the rpf is characteristic of a first-order gas-liquid transition. The enthalpy of this transition is somewhat higher than the hquid-gas transition in llie bulk, which should not be surprising since the interaction of the solid with the adsorbate should supply an extra energy. 

Recently, correlations between the standard formation enthalpies or the atomic standard formation enthalpies of the solid state versus the corresponding values of the gaseous state have been used (Method 3) [42,43]. For similar types of compounds of elements along one group with equivalent oxidation states linear correlations can be observed. More generally, this type of correlation is observed for different compounds of transition elements in their highest achievable oxidation state, see Figure 5. 

Method 7 Significant correlations exist between ionic radii in the solid state -or radii of electron orbitals of ions -and the sublimation enthalpies for various compound classes, especially for the halides. It is possible to calculate the standard sublimation enthalpy of transactinide compounds from their calculated ionic radii by making use of a radii-volatility correlation and of corresponding radii of the homologues [44], However, in this procedure it is important to use consistent sets of radii for all homologues, see e.g. Figure 7. 

Gschneidner [28,29] showed that the enthalpies of formation of several classes of lanthanide compounds can be correlated systematically as a function of atomic number. He pointed out [30] that the correlations for europium and ytterbium are anomalous because they are divalent in their metallic state but trivalent in the compounds. As shown in Figure 1, the enthalpies of formation of the lanthanide sesquioxides (or of any other class of compounds of R ) do not change in a smooth fashion as a function of Z or of the ionic radius of R. These enthalpies of formation correspond to the reactions that appear to be similar throughout the rare earths,... 

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