An interlaboratory comparison of the different realizations of the triple point of water (TPW) in Europe has been organized by EUROMET (Project No. 278). This project was based on the circulation of one TPW cell and an isothermal enclosure. The national metrology institutes of thirteen countries and the Bureau International des Poids et Mesures were involved in the work. Twenty-seven TPW cells were compared. Half of the results lie between −0.05 mK and +0.05 mK of the mean value, and all but two of the results are within 0.10 mK of the mean.
To improve the uncertainty of the aluminum fixed point, a study was launched by LNE-INM/CNAM in the framework of the EUROMET Project 732 "Toward more accurate temperature fixed points" (Coordinating laboratory: LNE-INM/CNAM, 17 partner countries). A new open cell was filled with aluminum of 99.99995% purity. A French laboratory carried out elemental analysis of the sample using glow discharge-mass spectrometry (GD-MS). The values of the equilibrium distribution coefficient k and of the derivative δT l /δc i l of the temperature of the liquidus line with respect to the concentration of impurity i will be obtained through collaboration with a French physical and chemical laboratory. In the past, some aluminum cells were opened after several melts and freezes. The aluminum ingot was sticking to the graphite crucible, indicating that physicochemical reactions had likely occurred between Al and C. To avoid this reaction, an effort was made to draw benefit from the Al 2 O 3 film that appears immediately on the surface of the aluminum ingot when it is exposed to oxygen. The open aluminum cell was tested in different furnaces and with different thermal insulator arrangements inside the fixed-point assembly. The observed drifts of the plateaux were always larger than the expected values. The cell was opened to inspect the aluminum ingot. The ingot was extracted easily, since no sticking to the crucible had occurred. The aluminum showed a very bright surface, but the presence of many "craters" throughout the thickness of the ingot was surprising. In some cases, the thermometer well was even apparent.
At high temperature (from 600 °C to 962 °C) calibration by comparison of platinum resistance thermometers (PRTs) is limited by the instability and the reliability of the standard high-temperature PRT and by the temperature uniformity in the working volume of furnaces equipped with comparison blocks. To improve its calibration-comparison capability, BNM-INM is studying the possibility of connecting several pressure-controlled heat-pipes, filled with different working fluids, simultaneously to the same pressure control system. The experimental apparatus, called a "temperature amplifier," is composed of three heat-pipes filled with sodium (Na), potassium (K), and dodecane (Do).
Comparisons of indium freezing point cells have been carried out by the EUROMET TC-THERM group as Projects Nos 391 and 712. The main objective was to establish the agreement between the realizations of the indium freezing point within different participating laboratories, to identify and eliminate possible discrepancies. The equipment has been made available by BNM–INM. Justervesenet coordinated project no 391, while project 712 was coordinated by BNM–INM. This paper is the final report of the results obtained, including the uncertainties in the comparisons and the degrees of equivalence between the laboratories.Main text.
To reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by EUROMET, according to the provisions of the CIPM Mutual Recognition Arrangement (MRA).
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