Measurement of Rh-C, Pt-C and Ru-C eutectic points by four national metrology institutes

The melting temperatures of three metal-carbon eutectics, rhodium-carbon, p latinum-carbon and ruthenium-carbon, were measured by four national metrolo gy institutes: the National Research Laboratory of Metrology (NRLM, Japan, now the National Metrology Institute of Japan, NMIJ), the National Institut e of Metrology (NIM, China), the National Measurement Laboratory (NML, Aust ralia), and the Korea Research Institute of Standards and Science (KRISS, R ep. of Korea). The same cells were measured using different radiation therm ometers and different high-temperature. carbon-tube furnaces by the four in stitutes, on their independently realized temperature scales. The results w ere compared to examine the performance of these high-temperature fixed poi nts and to determine their melting and freezing temperatures on the Interna tional Temperature Scale of 1990 (ITS-90). The measured fixed-point tempera tures were all within 0.4 degreesC of the calculated mean for each cell, an d were within each laboratory's estimated uncertainties. The mean values we re (1656.8 +/- 0.6) degreesC, (1737.4 +/- 0.3) degreesC and (1953.0 +/- 0.4 ) degreesC, respectively, for the melting plateaus of the Rh-C, Pt-C and Ru -C eutectic points, with the uncertainties given for k = 2.