Comment on 'Freezing Point Mixtures of H_2~(16)O with H_2~(17)O and Those of Aqueous CD_3CH_2OH and CH_3~(13)CH_2OH Solutions'

摘要

In a recent article,Kiyosawa [J.Solution Chem.33,323 (2004)] reports that the freezing points of isotopic mixtures of ordinary water and ~(17)O enriched water show an unexpectedly large linear dependence on the concentration of H_2~(17)O.Surprisingly,the constant of proportionality to the H_2~(17)O concentration is nearly five times larger than that of H_2~(18)O found in earlier studies by Kiyosawa [J.Solution Chem.20,583 (1991)].We show that the H_2~(17)O result is not consistent with other data or models.For example,a recent determination of the triple point temperature dependence on isotopic composition in naturally and artificially depleted waters [White et al.in Temperature,Its Measurement and Control in Science and Industry,Vol.7,D.C.Ripple,Ed.,AlP CP 684,221-226 (2003)] is consistent with the H_2~(18)O and D_2O results from Kiyosawa (1991) [White and Tew in Report of the 22nd Meeting of the Consultative Committee for Thermometry,Document CCT/03-21,BIPM,Severes,France,2003] but is inconsistent with the H_2~(17)O results from Kiyosawa (2004).Additionally,the results from Kiyosawa (1991) are close to what would be found in ideal solutions for those isotopic forms,whereas the H_2~(17)O proportionality from Kiyosawa (2004) is about 10 times larger than similarly predicted.One possible explanation is that the original ~(17)O enriched water sample contained a small amount of D_2O,and the sample,if available,should be subject to isotopic analysis to help resolve these inconsistencies.