Diffusion Cloud-Chamber Investigation of Homogeneous Nucleation

The critical supersaturations for the homogeneous nucleation of ethanol, methanol, hexane, and water were experimentally determined in the temperature range 235° to 295°K using a thermal diffusion cloud chamber. The design, construction, and operation of the chamber are described. A computer solution of the heat and mass flux equations determines the variation of pressure and temperature as a function of chamber height. The determination of the experimental critical supersaturation from chamber conditions is described and a comparison made with the values calculated from the Becker-Doering, Volmer, Zeldovich equation. Good agreement (usually within 5%) is obtained for ethanol, methanol, and hexane over a 60°K temperature range. Experimental difficulties limited the water data to a temperature range less than 15°K and agreement to within 15%.