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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.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



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.)
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
Cette etude fournit egalement une nouvelle methode pour estimer la tension interfaciale et la miscibilite dynamiques en introduisant des diffusivites contre-directionnelles dans le modele de Parachor traditionnel.
Keywords: interfacial tension, solubility, miscibility, mass transfer, diffusivity, vanishing interfacial tension (VIT) technique, mechanistic Parachor model
Ayirala and Rao (2004a) proposed a diffusivity incorporated mechanistic Parachor model to predict dynamic gas-oil interfacial tension in several crude oil-gas systems.
Our previously developed mechanistic Parachor model (Ayirala and Rao, 2004a) has been utilized to characterize the mass transfer mechanisms from interfacial tension measurements.
The Parachor model (Macleod, 1923; Sudgen, 1924; Weinaug and Katz, 1943) is the oldest among all the IFT prediction models and is still widely used in petroleum industry to estimate the interfacial tension between fluids.
Where [sigma] is the surface tension in mN/m, [[rho].sup.L.sub.M] and [[rho].sup.V.sub.M]are the molar densities of the liquid and vapour phases, respectively, in gmole/[cm/sup.3], [x.sub.i] and [y.sub.i] are the mole fractions of component i in the liquid and vapour phases, respectively and [P.sub.i] is the Parachor value of the component i.
In the Parachor model, Parachor values of pure components were used while calculating the interfacial tensions with an assumption that the Parachor value of a component in a mixture is the same as that when pure.
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.