The Relative Abundance of Hydrogen Isotopes

Samples of rain water collected at Princeton were decomposed by repeated passage over iron turnings heated to 510°C. The hydrogen formed was analyzed with a mass-spectrograph to determine the abundance ratio ${\mathrm{H}}^2$: ${\mathrm{H}}^1$. The first fraction of hydrogen to be liberated from a particular sample of the water yielded a value given by ${\mathrm{H}}^2$: ${\mathrm{H}}^1$=1: 6500 while the last fraction gave 1: 4500. Another sample was prepared in which the decomposition was carried to completion and all of the hydrogen collected. The abundance found in this sample was 1: 5000. It is believed that this last figure represents a close approximation to the true abundance ratio for natural hydrogen. The value 1: 30,000 previously reported by Bleakney for electrolytic hydrogen may be in agreement with these measurements when account is taken of the separation introduced by the electrolysis. A fairly extensive bibliography is given of recent work on the hydrogen isotopes.