Liquid-to-crystal nucleation: A new generation lag-time apparatus

The statistics of liquid-to-crystal nucleation are examined using a new generation automated lag-time apparatus denoted ALTA 4. Two modes of operation are described and implemented. A single 200 μl sample of distilled water is cooled repeatedly at a constant rate, α, until the sample freezes. This cycle is repeated many hundreds of times, to generate the reliable and reproducible statistics for nucleation. From a single experiment, under a single testable approximation, we extract the functional form which characterizes the average lag-time, 〈τ〉, as a function of the degree of supercooling ΔT below the equilibrium freezing temperature, Tf. These data and the analysis yield, from a single experiment, a profile for the average lag-time, 〈τ〉, as a function of change in temperature, ΔT. Identical results are obtained over more than an order of magnitude of cooling rates α, from 0.6 to 7.5 K min−1 (0.01–0.125 K s−1).