About isotope equilibrium between liquid and vapour phases.
A new semi-empirical formula was devised for liquid-vapour fractionation at thermodynamic equilibrium, which is valid for the whole temperature range, i.e. from the freezing to the critical temperature, Tc. The new formula contains three parameters (A, B and C) only: 10(3) ln alpha = ((A/T2) - (B/T))(1-x)+ C((Tc-T)/(T2))X, where X is the ratio of saturated vapour pressure at temperature T to the critical pressure. Physical reasons for the above formula are presented. The following numerical values of the parameters have been obtained by fitting the above expression to the experimental data from literature: A=1.3781x10(6), B=1.8876x10(3), C=3655.8 for 18O/16O, and A=18.993x10(6), B=40.798x10(3), C=18405 for D/H isotope fractionation. In both cases, X was calculated from the Van der Waals semi-empirical formula for vapour pressure, which has only one crude parameter: X=exp(-3.3(Tc-T/(T)).
Mass Spectrometry Laboratory, Institute of Physics, MarieCurie-Sklodowska University, Lublin, Poland. halas@tytan.umcs.lublin.pl
Stanislaw
S
Halas
D006859:Hydrogen / Q000737:chemistry*; D008956:Models, Chemical; D010103:Oxygen Isotopes / Q000737:chemistry*; D013500:Surface Tension; D013816:Thermodynamics; D014835:Volatilization; D014867:Water / Q000737:chemistry
D010103:Oxygen Isotopes; D014867:Water; D006859:Hydrogen