CONDENSATION OF WATER VAPOR IN A CLOUD CHAMBER.

The condensation of water vapor was investigated in a cloud chamber by measuring pressure as a function of time. A dense mist reproducibly formed, suggesting homogeneous nucleation occurred in the present work. Nucleation at low temperature approximately 230K was significantly faster than the 0.4 particlescc predicted by the classical theory of nucleation, and the classical theory therefore is suspect. The present results were compared to several models of condensation kinetics obtained by combining collisionfrequency growth kinetics with the recent 10 to the 20th power -revised nucleation theory amended for various types of monomer loss. Results faintly suggested that ultra-small water clusters are about 10 to the minus 3rd as stable as predicted by macroscopic cluster thermodynamics. Compression of the bulk gas due to heat conduction from the hot walls was appreciable, both during and after expansion. Previous work which appeared to support the classical nucleation theory probably is obscured by heat conduction during expansion. Author