Homogeneous nucleation rates for n-butanol

Homogeneous nucleation rates of n-butanol in argon were measured in an expansion chamber maintaining pressure, temperature, and vapor supersaturation practically constant during nucleation periods of about 1 ms. Tables of the homogeneous nucleation rates J in the range 105<J/cm−3 s−1<109 as function of supersaturation S in the temperature range 225<T/K<265 are presented along with the other experimental measurables. For the temperatures considered the equilibrium vapor pressure of n-butanol and the surface tension are known with sufficient accuracy. Accordingly, a quantitative comparison of the experimentally obtained nucleation rates with the predictions of the classical theory could be performed. The agreement is sufficient. The reported individual J−S curves were obtained at selectable constant temperatures. From the slopes of the isothermal J−S curves the number of molecules in the critical clusters were determined without reference to any specific nucleation theory. Conceiving the clusters as small droplets one finds, using macroscopic liquid density and surface tension, that the Gibbs–Thomson equation provides remarkably good predictions even for droplets with radii down to 10 Å.