An International Intercomparison of Fixed Points by Means of Sealed Cells in the Range 13.81 K–90.686 K

Abstract

An International Intercomparison of Fixed Points by Means of Sealed Cells has been conducted under the auspices of the Comité Consultatif de Thermométrie (CCT) between 1978 and 1984. Forty-one sealed cells, realizing the triple point of seven different substances, defining both primary fixed points of the IPTS-68 and secondary fixed points in the temperature range from 14 K to 90 K, were supplied by nine laboratories. They were measured in eleven national laboratories around the world, against the fixed points realized in these laboratories (both in open cryostats or in other sealed cells). Some 150 independent series of data were produced, from almost 300 melting experiments, representing some 2,300 equilibrium temperature values. The basic sets of results are presented, concerning the agreement between different cell realizations and the comparison of national IPTS-68 realizations. Data connecting the results of this intercomparison with that performed at NPL in 1975 using calibrated thermometers are also given.