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

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 H-2 isotope effect. We manufactured five triple point cells with prepared water mixtures with a range of H-2 isotopic abundances encompassing widely the natural abundance range, while the O-18 and O-17 isotopic abundance were kept approximately constant and the O-18 - O-17 ratio was close to the Meijer-Li relationship for natural waters. The selected range of H-2 isotopic abundances led to cells that realised TPW temperatures between approximately -140 mu K to + 2500 mu K 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 delta H-2 correction parameter of A(2H) = 673 mu K / (parts per thousand deviation of delta H-2 from VSMOW) with a combined uncertainty of 4 mu K (k = 1, or 1 sigma).