“…The vapour pressure of water enriched in heavy isotopes of oxygen has been investigated many times, mostly to obtain values of the relative volatility a* using the Rayleigh distillation method 1, 1 6 9 18,22, 25 or high efficiency distillation c0lumns.3~ 4, 8,17,20,23 These methods are of limited precision and may suffer from appreciable systematic errors.…”