CXXII.—Some physical properties of radium emanation

On the vapour pressure of radon

“…In other words, in the Wagner equation, p c can be treated as one further adjustable parameter as well as the four parameters a i [14][15][16]. Gray and Ramsay [2] carried out two series of experiments: one of 28 measurements of the vapour pressure of radon spanning temperatures from (273 to 375) K; and a second one of 14 points encompassing the interval from (263 to 377.5) K. In the light of present standards, these values of the measured pressure are somewhat scattered and their temperature scale is difficult to assess. By using both sets of values and the critical temperature measured by Gray and Ramsay, which in our assessment should be T c = 377.7 K in ITS-90, equation (1) with n = 2.5 and m = 5 leads to a 1 = À5.1737, a 2 = 1.4220, a 3 = À5.1052, a 4 = 12.3409, and to an estimate of p c = (6189 ± 168) kPa.…”

“…From the values compiled by Stull [5], using this procedure in conjunction with the vapour pressure equation (1) with the a i parameters noted above (and a reasonable estimate of T tr ), we arrive at converging values of the triple-point coordinates: T tr = (200.0 ± 0.1) K and p tr = (58.8 ± 0.6) kPa. The a 0 i parameters obtained for equation (2) are: a 0 1 ¼ À10:3220; a 0 2 ¼ 1:8802; a 0 3 ¼ À7:4723; and a 0 4 ¼ À15:3580. The standard deviation for the sublimation pressure obtained from this fitting is r(ln p) = ±0.0068.…”

“…These experiments were carried out using small or very small samples of the gas, usually of purity not guaranteed and using techniques now outdated, despite the care with which they were performed and reported. For the phase equilibria concerned, it has been recognized [1] that the measurements made on the vapour pressure of liquid radon by Gray and Ramsay [2] are still the most extensive and reliable ones. As far as we are aware no other set of careful experimental values of this property has been reported in recent times.…”

Novel correlations between the critical constants of the noble gases

“…In the case of Rn, the values listed for P c and T c are from the recent re-evaluation by Ferreira and Lobo [14] of the early data (and still apparently the only precise ones) that were obtained by Gray and Ramsay [15]. From its format, the value for V c of 140.00 cm 3 mol −1 listed by Poling et al [13] is evidently an estimate; the value given in Table 1 is an extrapolation from the present Case C linear correlation for the quartet Ne-Xe (Section 2.4).…”

“…c Rn: the values of Pc and Tc are from the re-evaluation by Ferreira and Lobo [14] of the original data of Gray and Ramsay [15]. The value of Vc has then been estimated from Eq.…”