Vapour pressure and ideality of the equimolar mixture of H₂O and D₂O

Abstract

The pressure differences between H₂O and the equimolar H₂O-D₂O mixture were measured between 5 and 90°C and the experimental data can be represented by the equation

                  In(p_H2O/p_mix) = 0.076624-88.161/T+25972/T²

where T is the absolute temperature. For comparison the vapour-pressure differences between pure H₂O and D₂O were also determined. The results show that the H₂O-HDO-D₂O liquid mixture does not deviate from the ideal behaviour within the limits of the experimental data. The present investigation supports the earlier conclusion that the law of the geometric mean for the vapour-pressure isotope effect in the series H₂O, HDO and D₂O is not obeyed.