Composition of Mixed Vapors in the Cloud Chamber

Abstract

The composition of the alcohol-water vapors commonly used in cloud chambers differs from that of the liquid mixtures from which they are produced. This must be considered when ranges or cross sections are to be calculated. Curves are presented for the case of ethanol and water, showing, for various temperatures, the vapor pressure of each constituent as a function of the percent volume of alcohol in the liquid. Attention is called to errors incurred if the cycle of operation is so brief that the vapors do not come up to equilibrium concentration between expansions.