Binary N-octanol-sulfur hexafluoride nucleation

Recently, the accuracy of vapor nucleation rate measurements has increased substantially. However, when experimental conditions become close to the va lues to the critical parameters of investigated systems, significant discre pancies were found between the experimental results and theoretical predict ions. Some studies have found agreement between results and theory only wit hin a narrow range of nucleation conditions. Therefore, it is appropriate t o investigate the nucleation of additional systems to obtain new informatio n to guide nucleation theory development. Alcohols are the most studied cla ss of chemical compounds, but currently there are no experimental data on n -octanol vapor nucleation. The present study is devoted to the investigatio ns of the homogeneous nucleation of the n-octanol in sulfur hexafluoride. C omparison of the critical pressures for binary mixture with the Laplace pre ssure calculated in the droplet approximation using the bulk liquid surface tension shows that the carrier gas has a more active role in the nucleatio n than assumed by classical theory. A very high Laplace pressure in the cri tical embryo is calculated in the droplet approximation. When compared with the highest possible critical pressure for the binary system under investi gation, the problems associated with calculating the critical embryo excess energy using the bulk liquid surface tension are revealed. Disagreement of the experimental results with predictions of classical nucleation theory, Dillmann-Meier theory, or any other theory reveals the same basic problems. These results suggest that it is appropriate to consider the general probl em of vapor-liquid nucleation in a carrier gas including the estimation of the size and temperature dependence of the critical embryo excess energy as a binary nucleation problem instead of that of a single component. Theorie s for single-component vapor nucleation should be compared with the truly s ingle-component vapor nucleation experimental results. (C) 2001 American In stitute of Physics.