Application of a Scaled Homogeneous Nucleation-Rate Formalism to Experimental Data at T≪T\u3csub\u3ec\u3c/sub\u3e

It is pointed out that for temperatures T\u3c0.5Tc, where Tc is the critical temperature, the classical steady-state nucleation-rate formalism of Becker and Doring predicts an approximate critical supersaturation ratio Scr (for the onset of nucleation) given by lnScr/Ω3/2~0.53(Tc/T-1)3/2. Ω is a material-dependent quantity approximately equal to the excess surface entropy per molecule. For most substances Ω ~ 2.0 and for associated liquids Ω ~ 1.5.The experimental data (for nucleation from vapor to liquid) from diffusion chamber and nozzle beam studies are found to be consistent with the above expression. The classical theory also predicts that for a supersaturation ratio S corresponding to constant J, lnS/lnScr-1 ~ lnJ/2lnJc, where lnJc is a quantity evaluated at the critical point and is ~ 72 for most materials. Expansion cloud-chamber data for nonane, toluene, and water are also found to be consistent with these approximate scaling laws