Triple-Point Temperature and the Isotopic Composition of Three Commercial Neon Gases

Abstract

The triple-point temperature of neon, T tp−Ne , is known to have dependence on the isotopic composition. Recently, the Technical Annex for the International Temperature Scale of 1990 was updated to specify the method of correction for the isotopic reference ratio of neon. In this study, to confirm this correction in the Technical Annex independently, the effects of the isotopic composition of neon on T tp−Ne for three commercial neon gas sources were studied. For the measurement of the isotopic composition, a gas mass spectrometer was used to compare the sample gases with a reference neon gas whose isotopic composition was known with high precision by a gravimetric method. For the measurement of T tp−Ne , an open-cell type cryostat for the realization of low-temperature fixed points was used. The physical cell and the thermal environment around it remained very similar for all T tp−Ne measurements with the neon gases due to the nature of the open-cell type system. Therefore, the difference in T tp−Ne among different samples could be measured with a relatively low uncertainty, canceling many systematic effects that are common to all measurements. Our result was consistent with the correction in the Technical Annex. Furthermore, because one of the commercial neon gases was the bottle that was used for KRISS measurements in the international comparison CCT-K2, it is now possible to correct the measurement for the reference isotopic ratio and compare it with other measurements for which isotopic composition data are available.

An inter-comparison of isotopic composition of neon via chemical assays and thermal analyses (IUPAC Technical Report)

“…The basic outcomes of these studies are summarized in Table 2 (and Tables 4, 5 in Online Appendices A2, A3), and in Figs. 3,[4][5][6][7][8][9][10][11][12][13] in Online Appendices A2, A3)-see [2] for some preliminary comments. Figure 2 visually represents the variation of the assay results on replication for the same sample, either by the same laboratory or in different laboratories.…”

“…In comprehensive studies lasting from 2003 to 2014 the effect of isotopic composition on the triple point temperature was tested on neon of different isotopic compositions obtained from commercial sources [http://www.euramet.org/research-innovation/search-research-projects/details/?eurametCtcp_project_ show[project]=648(EUROMET Project 770: Determination of an accurate T tp vs. x(isotopic) relationship for neon)]. These studies involved 10 National Metrology Institutes (NMIs) and three chemical-assay laboratories [1][2][3][4][5][6][7][8][9][10][11]. The relevance of the isotopic effects in thermometry has already been discussed in depth in [8] and references therein.…”

“…The isotopic composition studies comprised: -Analytical assays from 3 laboratories on the isotopic composition of samples from 31 bottles of high chemical purity commercial neon, as well as on the chemical impurities of some of these samples [1,[11][12][13][14]; -Thermal analyses from 9 laboratories on 39 samples, almost all permanently sealed in metal cells (ensuring full physical-chemical sample stability), for the determination of the liquidus-point temperature of the triple point [8]. The sealing is so far tested to perform up to and over 40 years [15], with an accuracy up to or better than about 50 μK; Analytical assays and thermal analyses from bottles of artificial mixtures of high-purity 22 Ne in 20 Ne, certified by the gravimetric method (only the mixture with 10 % 22 Ne relative amount fraction is included here) [12].…”

An inter-comparison of isotopic composition of neon via chemical assays and thermal analyses (IUPAC Technical Report)

“…In comprehensive studies lasting from 2003 to 2014 the effect of isotopic composition on the triple point temperature was tested on neon of different isotopic compositions obtained from commercial sources [12]. These studies involved 10 National Metrology Institutes (NMIs) and three chemical-assay laboratories [1][2][3][4][5][6][7][8][9][10][11]. The relevance of the isotopic effects in thermometry has already been discussed in depth in [8] and references therein.…”

“…The isotopic composition studies comprised: -Analytical assays from 3 laboratories on the isotopic composition of samples from 31 bottles of high chemical purity commercial neon, as well as on the chemical impurities of some of these samples [1,11,[13][14][15]; -Thermal analyses from 9 laboratories on 39 samples, almost all permanently sealed in metal cells (ensuring full physical-chemical sample stability), for the determination of the liquidus-point temperature of the triple point [8]. The sealing is so far tested to perform up to and over 40 years [16], with an accuracy up to or better than about 50 μK; Analytical assays and thermal analyses from bottles of artificial mixtures of high-purity 22 Ne in 20 Ne, certified by the gravimetric method (only the mixture with 10 % 22 Ne relative amount fraction is included here) [13].…”