Vapour pressure of H218O ice (–50 to 0°C) and H218O water (0 to 170°C)
- 1 January 1977
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 73, 1505-1509
- https://doi.org/10.1039/f19777301505
Abstract
The vapour pressure difference between H2 16O and highly enriched H2 18O samples was measured directly with a capacitance type differential monometer between –50 and 80°C and with a U-type mercury manometer between 80 and 170°C. Data for the vapour pressure isotope effect in the ice range gave a good fit to the equation ln([graphic omitted])= 3.710/T+ 0.00132 (223 < T < 273), and those in the liquid range to ln ([graphic omitted])= 5.869/T– 0.0108 (293 < T < 443). From the temperature dependence of the vapour pressure ratios the isotope effects on the heat of sublimation and evaporation were calculated. At the melting point Δ(ΔHsub)= 31 J mol–1 while Δ(ΔHevap)= 77 J mol–1 were found. The results are compared with earlier measurements and with data for the HOH/DOD system, where the isotope effect on the heat of fusion is much larger and of opposite sign.Keywords
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