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The molecular weight of a liquid times the fourth root of its surface tension, divided by the difference between the density of the liquid and the density of the vapor in equilibrium with it; essentially constant over wide ranges of temperature.



the quantity that may reflect certain physical properties of substances, especially nonassociated organic liquids. The parachor was first proposed by the British scientist S. Sugden in 1924. It is calculated according to the formula P = ¼/(ρ1 — ρ2), where M is the molecular mass of the substance, σ is the surface tension, and ρ1 and ρ2 are the densities of the liquid and saturated vapor, respectively.

The parachor is an additive quantity; that is, a compound’s net parachor is the algebraic sum of the parachors of the compound’s constituent parts—individual atoms, atomic groups, or interatomic bonds. The quantities that are associated with the subunits of a compound can be obtained from handbooks. The parachor provides an approximate value for the surface tension of a liquid and is also one of the parameters used to determine the structure of organic compounds.


Bretsznajder, S. Svoistva gazov i zhidkostei. Moscow-Leningrad, 1966. (Translated from Polish.)
Fizicheskie metody organicheskoi khimii, vol. 1. Edited by A. Weissberger. Moscow, 1950. Page 215. (Translated from English.)
References in periodicals archive ?
Recently, Ayirala and Rao (2004a) proposed a mechanistic Parachor model for reliable prediction of dynamic gas-oil interfacial tensions in multicomponent crude oil-gas mixtures by introducing the ratio of diffusivity coefficients between the fluid phases raised to an exponent (n) for mass transfer effects into the original Parachor model.
This condition of equal mass transfer in both the directions of vaporization and condensation appears to be most common in binary mixtures where the conventional Parachor model has shown to result in reasonably accurate interfacial tension predictions (n = 0 in the mechanistic Parachor model).
The value of the exponent (n) in the proposed mechanistic model was obtained by equating the mass transfer enhancement parameter (k), the correction factor to the original Parachor model at which the objective function (the sum of weighted squared deviations between the original Parachor model predictions and experimental IFT values) becomes minimum, to the ratio of diffusivity coefficients between the fluid phases.
The measured densities of the equilibrated fluid phases and the pure component Parachor values reported by Danesh (1998) were used during gas-oil IFT calculations.
The comparison between IFT predictions from the Parachor model and the experiments at various pressures is given in Table 2.
The mechanistic Parachor model has been applied to improve the IFT predictions in this gas-oil system by accounting for counter-directional mass transfer effects.
The comparison between experiments and the predictions obtained using the exponent from the compositional data of live decane in the mechanistic Parachor model is given in Table 4 and shown in Figure 9.
These near equilibrium interfacial tensions appear to be amenable to calculations using the diffusivity included mechanistic Parachor model and hence can be used to predict fluid-fluid miscibility using the VIT technique.
The dynamic gas-oil IFT and miscibilities measured were modelled using the mechanistic Parachor model.
Rao, "Application of a New Mechanistic Parachor Model to Predict Dynamic Gas-Oil Miscibility in Reservoir Crude Oil-Solvent Systems," SPE Paper 91920, in "Proc.
Sarkar, "A Modified Scaling Law and Parachor Method Approach for Improved Prediction of Interfacial Tension of Gas-Condensate Systems," SPE Paper 22710, in "Proc.
Comparison of IFT measurements with parachor model in n-decane-C[O.