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An expansion cloud chamber was used to measure the homogeneous nucleation rate for water over a wide range of temperature from 230–290 K and nucleation rates of 1–106 drops cm−3 s−1. The comprehensive and extensive nature of this data allows a much more detailed comparison between theory and experiment than has previously been possible. The expansion chamber technique employs continuous pressure measurement and an adiabatic pulse of supersaturation to give the time history of supersaturation and temperature during the nucleation. The resulting drop concentration is determined using photographic techniques. The experimental observations are presented in tabular form and from them an empirical nucleation rate formula is determined: J=S2 exp[328.124−5.582 43T+0.030 365T2−5.0319E−5T3 −(999.814−4.100 87 T+3.010 84E−3 T2)ln−2S], where J is the nucleation rate in units of drops cm−3 s−1. S is the supersaturation ratio and T is the temperature in K.

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