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Homogeneous Nucleation In Supersaturated Vapors Of Polar Molecules: Acetonitrile, Benzonitrile, Nitromethane, And Nitrobenzene, D. Wright, R. Caldwell, C. Moxely, M. S. El-Shall Jan 1993

Homogeneous Nucleation In Supersaturated Vapors Of Polar Molecules: Acetonitrile, Benzonitrile, Nitromethane, And Nitrobenzene, D. Wright, R. Caldwell, C. Moxely, M. S. El-Shall

Chemistry Publications

The critical supersaturations (S c ) required for the homogeneous nucleation of acetonitrile, benzonitrile, nitromethane, and nitrobenzene vapors have been measured over wide temperature ranges using a thermal diffusion cloud chamber. At T r =0.44, the experimental results are higher than the predictions of the classical nucleation theory by 20% (CH3NO2), 50% (CH3CN), 57% (C6H5NO2), and 112% (C6H5CN). This trend correlates well with the dipole moments and to a lesser extent with the polarizabilities of these substances. Corresponding states of simple fluids and …


Analysis Of Homogeneous Nucleation Data Of Polar Molecules: Vapor Association, Dipole Orientation, And Elongated Clusters, D. Wright, M. S. El-Shall Jan 1993

Analysis Of Homogeneous Nucleation Data Of Polar Molecules: Vapor Association, Dipole Orientation, And Elongated Clusters, D. Wright, M. S. El-Shall

Chemistry Publications

In this paper we present the results of several theoretical models examined in order to explain the observed systematic deviations of the homogeneous nucleation of highly polar substances from the predictions of the classical nucleation theory (CNT). It is found that molecular association in acetronitrile or nitromethane vapor cannot explain the observed higher supersaturations. Similarly, the use of virial coefficient data to obtain a size dependent surface energy correction factor does not reproduce the experimental results. It is shown that orientation of the surface dipoles within the spherical droplets results in higher supersaturations in agreement with the experimental findings. We …