Accurate experimental determination of the isotope effects on the triple point temperature of water. I. Dependence on the 2H abundance

Abstract

Variation in the isotopic composition of water is one of the major contributors to uncertainty in the realization of the triple point of water (TPW). Although the dependence of the TPW on the isotopic composition of the water has been known for years, there is still a lack of a detailed and accurate experimental determination of the values for the correction constants. This paper is the first of two articles (Part I and Part II) that address quantification of isotope abundance effects on the triple point temperature of water. In this paper, we describe our experimental assessment of the 2H isotope effect. We manufactured five triple point cells with prepared water mixtures with a range of 2H isotopic abundances encompassing widely the natural abundance range, while the 18O and 17O isotopic abundance were kept approximately constant and the 18O − 17O ratio was close to the Meijer–Li relationship for natural waters. The selected range of 2H isotopic abundances led to cells that realised TPW temperatures between approximately −140 μK to +2500 μK with respect to the TPW temperature as realized by VSMOW (Vienna Standard Mean Ocean Water). Our experiment led to determination of the value for the δ2H correction parameter of A2H = 673 μK / (‰ deviation of δ2H from VSMOW) with a combined uncertainty of 4 μK (k = 1, or 1σ).