George T. Furukawa

Guidelines for Realizing the International Temperature Scale of 1990 (ITS-90) | NIST

This Technical Note describes the International Temperature Scale of 1990 (ITS-90) that became the official international temperature scale on 1 January 1990, superseding the previous scales, and provides information on how the scale may be realized at different levels of accuracy. The ITS-90 extends upward from 0.65 K, is in close agreement with the Kelvin Thermodynamic Temperature Scale, has much improved continuity, precision and reproducibility throughout its ranges over that of previous scales, and has subranges and alternative definitions in certain ranges that greatly facilitate its use. In addition to a description of the ITS-90 and how it can be realized, there are included in this document reproductions of some articles and excerpts from documents concerned with the ITS-90. The composition of the Comite Consultatif de Thermometrie (CCT) of the Comite International des Poids et Mesures (CIPM) at the time of the adoption of the ITS-90 is given. The differences between the temperatures on the ITS-90 and those on the International Practical Temperature Scale of 1968, Amended Edition of 1975, [IPTS-68(75)] and those on the 1976 Provisional 0.5 K to 30 K Temperature Scale (EPT-76) are tabulated. Measurement procedures for realizing the ITS-90 throughout the various ranges of the scale are given. Also, for the most important temperature region, the region of the platinum resistance thermometer (PRT) , computational examples are given for determining the coefficients of the relevant deviation equations for PRTs calibrated at various sets of fixed points. The effects of the introduction of the ITS-90 on electrical reference standards are addressed also.

Critical Analysis of Heat—Capacity Data and Evaluation of Thermodynamic Properties of Ruthenium, Rhodium, Palladium, Iridium, and Platinum from 0 to 300K. A Survey of the Literature Data on Osmium.

The literature sources of heat‐capacity data on ruthenium, rhodium, palladium, osmium, iridium, and platinum have been compiled and the data critically analyzed. Except for osmium where data are lacking, best values of thermodynamic properties have been evaluated between 0 and 300 K from the analyses. The literature values of heat capacity, the electronic coefficient of heat capacity (γ), and the zero K limiting Debye characteristic temperature (θD(0)) are compared. The sources of data are tabulated chronologically along with the temperature range of measurements, purity of sample, and the pertinent experimental procedures used. A bibliography of the references is listed.

Vapor Pressures of Natural Neon and of the Isotopes 20Ne and 22Ne from the Triple Point to the Normal Boiling Point

Apparatus design and procedures are described for the determination of the vapor pressures of naturally occurring neon (natNe) and the pure isotopes 20Ne and 22Ne from their triple points (TP) to their normal boiling points (NBP). The data have been fitted to vapor-pressure equations with root-mean-square deviations of ? 2.5 to ? 4.7 N/m2 (? 0.019 to ? 0.035 mmHg). The TP pressures (P) and the TP and NBP temperatures (T) were found to be: TP NBP P T, K T, K natNe 43332 ? 13 N/m2 (325.02 ? 0.10 mmHg) 24.553 ? 0.001 27.096 ?0.001 20Ne 43326 ? 13 N/m2 (324.97 ? 0.10 mmHg) 24.540 ? 0.001 27.084 ? 0.001 22Ne 43654 ? 13 N/m2 (327.43 ? 0.10 mmHg 24.687 ? 0.001 27.211 ? 0.001 (The temperatures are in terms of the NBS-1955 provisional temperature scale. The figures after the ? symbol indicate estimated uncertainties). The calculated vapor pressures of the isotopic natNe, based on Raoults law of solution and the observed vapor pressures of the pure isotopes, are in agreement within the combined precision of the measurements with the observed values of natNe.

An international intercomparison of fixed points by means of sealed cells in the range 13.81 K-90.686 K

An International Intercomparison of Fixed Points by Means of Sealed Cells has been conducted under the auspices of the Comite Consultatif de Thermometrie (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.

Effects of different methods of preparation of ice mantles of triple point of water cells on the temporal behaviour of the triple-point temperatures

We report results of an investigation of the temporal variation of the temperature of triple point of water (TPW) cells, in which the ice mantles were prepared by four different techniques using: (i) solid CO2, (ii) an immersion cooler, (iii) liquid-nitrogen-cooled rods, and (iv) liquid nitrogen (LN), first passing cold nitrogen vapours and then LN directly into the wells of the cells. The temperature of the TPW cell water was either approximately 274 K or 295 K when the freezing of the ice mantle was started. No visible cracks formed during the preparation of any of the mantles using the crushed solid-CO2 or the immersion cooler method, but all of the ice mantles cracked when prepared using the LN-cooled-rod and LN techniques. The cracked mantles, however, soon healed. Initially, the temperatures of the mantles prepared by the four methods varied, but after about three or four days they agreed to within 0,1 mK; after one week they agreed to within 0,03 mK, except for mantles prepared by the LN technique, for which nine days were once required for one of the mantles; after eleven days, the results were practically the same. It appears that the temperature variations observed during the first few days following the preparation of mantles could be caused by a combination of (i) temperature decrease due to introduction of strains in the ice and to formation of fine ice crystals during the preparation of the mantle and (ii) temperature increase due to the relief of strains and the gradual conversion of fine ice crystals to larger ice crystals. Mantles that underwent severe cracking thereby released most of the energy associated with the large strains introduced during preparation of the mantle.

Normal Boiling Point and Triple Point Temperatures of Neon

The normal boiling point and triple point temperatures and the triple point pressure of neon were found to be 27.096 ± 0.001 K and 24.553 ± 0.001 K, and 43332 ± 13 N/m2 [325.02 ± 0.10 mm Hg (0 °C)], respectively. (The temperatures are in terms of the NBS-1955 provisional temperature scale. The figures after the ± symbol indicate estimated uncertainties.) The triple point pressure is in accord with the more recent values, but the normal boiling point and triple point temperatures deviate significantly from those of previous investigators.

Heat Capacity near the Consolute Point in Solid CH4–Ar

Measurements are reported of the heat capacity at saturated vapor pressure (essentially Cp) of the system CH4–Ar near its solid‐solid consolute point (62°K, 65% Ar). In contrast to the behavior of the heat capacity at binary liquid consolute points, where there are striking anomalies, no large increase was observed for CH4–Ar. An abrupt increase of only about 13% occurred in the heat capacity near the transition. The possibility that the anomaly is suppressed by lattice strain effects is discussed.

Recent Advances in the Realization and Dissemination of the ITS-90 Below 83.8058 K at NIST

Recent advances in our knowledge of the International Temperature Scale of 1990 (ITS-90), as realized and maintained at the National Institute of Standards and Technology (NIST), are briefly reviewed. As a result of these advances, the NIST disseminated version of ITS-90 has recently undergone small adjustments below 83.8058 K. These adjustments are all at the sub-millikelvin level and reflect the inclusion of recent data on ITS-90 realizations and intercomparisons of reference thermometers. Specifically, developments in the realization of ITS-90 fixed points, gas thermometry, and vapor pressure thermometry at NIST have significantly improved our knowledge of scale non-uniqueness and dissemination uncertainty in the lowest temperature ranges. We briefly describe the present status of ITS-90 realizations at NIST and which definitions are currently being disseminated. Our procedures for calibration of standard reference thermometers for cryogenic use are reviewed and our updated assessments of calibration uncertainties are presented. These include calibration of Standard Platinum Resistance Thermometers (SPRTs) of the capsule type between 13.8033 K and 273.16 K, and of Rhodium-Iron Resistance Thermometers (RIRTs) between 0.65 K and 83.8058 K. In addition, we preview a new Standard Reference Material® (SRM®) project which will make available “as defined” ITS-90 calibrated capsule SPRTs through the MST SRM program. These continuing advances in scale realization and dissemination at NIST will improve the accuracy and availability of ITS-90 standards throughout the cryogenic engineering community.

Report on the Sixth International Symposium on Temperature

This is a report on the Sixth International Symposium on Temperature which was held in Washington, DC, USA. March 15-18, 1982. It includes a brief introduction indicating the timeliness of the Symposium, its sponsors and the publication of its proceedings. The remainder of the report is devoted to a summary of the Plenary and Technical Sessions of the Symposium.