Deuterium content of natural waters and other substances

A mass spectrometric method for the accurate determination of the hydrogen-deuterium ratio has been developed. It is possible to determine this ratio to ± 0.10% using material of “normal abundance”, i.e., 1 part D in 6700 parts H. Samples as small as 0.1 mg H2 (0.001 ml H2O) can be run. Natural evaporation and condensation that have been shown to fractionate the oxygen isotopes also fractionate the hydrogen isotopes. The ratio of these two fractionations is equal to the ratio between the ratios of the vapour pressures of H2OHDO and of H2O16H2O18. Ocean waters range from 0.0153 to 0.0156 mole % deuterium, whereas fresh waters of the United States range from 0.0133 to 0.0154 mole % deuterium. A measurement of Yellowstone Park fumarole gases gives a minimum temperature of 400° for the equilibrium H2O + HD = HDO + H2 in the gases.