Hiromu Wakeshima

Time Lag in the Self-Nucleation

An approximate but simple and general treatment of the time lag in self-nucleation is given. In this method the relation to be satisfied approximately by the rate of nucleation in non-steady state is obtained and solved without first seeking the distribution of embryos. This calculation, when applied to the problem of condensation of water vapor in a high degree of supersaturation, gives a time lag of the same order of magnitude as that obtained by Probstein who solved the problem in ordinary way. Time lag of self-nucleation in the case of transformation in a solid is also computed. Certain limitation has been set therefrom to the validity of the notion of “athermal nucleation” as proposed by Turnbull et al., which presumes a large temporary lagging in the change of embryo distribution when, e.g., metals are quenched in phase transformations.

Fog Formation due to Self Nucleation (II)

In the previous paper 1) a theory was presented by the author which concerns the fog formation due to self nucleation in adiabatically expanded dust- and ion-free moist air. In this theory the change of temperature of the air after expansion was not taken into account. In this report the influence of the rise in temperature of the air after an initial cooling due to the heat transmission from outside of and the heat liberation inside the gas is treated in an approximate way and the results discussed.

Growth of Droplets and Condensation Coefficients of Some Liquids

The process of growth of fog droplets in suppersaturated vapor was investigated, making use of photoelectrical measurements on the time rate of increase in the intensity of scattered light by the droplets of developing fog. The experimental results were compared with the theoretical concerning the growth of fog droplets in supersaturated vapor which contain the condensation coefficient as a parameter. The values thus obtained are about 0.02 for water, 0.004 for methyl alcohol and 0.01 for ethyl alcohol.

Spontaneous Condensation in a supersonic Flow of Humid Air

The problem of the spontaneous condensation of water vapor in a supersonic flow of moist air is approximately solved in a way similar to those given previously 1) , on the basis of Becker-Dorings equation for the stationary rate of self-nucleation and also based on the law of droplet growth used before. Comparison of the theoretical prediction with experimental results given by Head 2) shows a considerably good agreement and thus it is revealed that major part of the delay of the appearance of condensation, from which some doubt has been cast over 3) the validity of Beckers formula in such cases, can be explained plausibly without the notion of time lag in the self-nucleation.

Development of Emulsions due to Self Nucleation

Based on the formulae for the absolute rate of self-nucleation in condensed systems and also for the growth of droplets derived by the author, the process of development of emulsions in solutions supersaturated with dissolved liquid, when the meta-stable state is broken by self-nucleation, is approximately treated, in a way similar to that given previously 1) . The relations giving such as the threshold condition for the appearance of turbidity and the number density of droplets are obtained.