Study of the Isotopic Disproportionation Reaction between Light and Heavy Water Using a Pulsed-Molecular-Beam Mass Spectrometer

Isotopic exchange equilibrium in the disproportionation reaction H2O+D2O=2 HDO was studied at 0° and 25° and over a range of deuterium compositions using a pulsed-molecular-beam mass spectrometer. The equilibrium constant K was found to be 3.75±0.07 at both temperatures. The pulsed-beam mass spectrometer was shown to be effective in minimizing the ``memory effect'' in the mass spectrometer. The experimental K is shown to be consistent with equilibrium constants for similar isotopic disproportionation reactions and with current theory.