Using the 100% relative‐humidity technique for controlling the mole function of water vapor, the Napier (relaxation) frequency of oxygen has been measured as a function of the mole fraction of various water vapors, consisting of pure H2O, pure D2O, and three mixtures thereof. Pure H2O gives, as is well known, a quadratic in H, the mole fraction; pure D2O gives a linear relation down to 0.7×10−3. The mixtures show a linear relation above 1.5×10−3 and a curvilinear approach to zero below that. Calculation indicates that the heterogeneous molecule HDO is far more effective as a thermal equilibrator for oxygen than either of its homogeneous parents. Quantitatively, with (f/p)m in cps per atm and h in mole fraction ×103, the results are:
100% H2O: (f/p)m = 7+183h+132h2;
50% D2O: (f/p)m = −664+1100h;
80% D2O: (f/p)m = −490+908h;
92% D2O: (f/p)m = −250+585h(above h = 1.3);
92% D2O: (f/p)m = 7+275h+100h2(below h = 1.3);
99.8% D2O: (f/p)m = −85+385h.