IT has been stated that deuterium can be concentratsed much more efficiently by the spontaneous atmospheric evaporation of water than by boiling1. This suggestion is based on an experiment in which Pozna water, by spontaneous evaporation to 1/40 of its volume, gave a residue claimed to contain 1.65 per cent of deuterium. The experiment would appear to be incorrect, however, for even assuming semipermeable membrane separation (α = ∞) the proportion of deuterium in Poznan water would, according to this experiment, have the highly improbable value 1/2,500. Of course, the separation coefficient, α, cannot be infinity: under ideal conditions it could amount to the isotopic vapour pressure ratio. Taking α = 1.15 as an outside figure, the deuterium content of Pozna water, according to the reported evaporation experiment, becomes 1/100.
T. Tucholski, NATURE, 134, 29, July 7, 1934.
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HUGHES, E., INGOLD, C. & WILSON, C. Concentration of Heavy Water by Spontaneous Evaporation. Nature 134, 142 (1934). https://doi.org/10.1038/134142a0