Differences between Thermodynamic Temperature andt(IPTS-68) in the Range 230°C to 660°C

Abstract

Determination of the differences between the Kelvin Thermodynamic Temperature Scale (KTTS) and the International Practical Temperature Scale of 1968 (IPTS-68) in the range from 230 "C to 660 "C has been accomplished by gas thermometry. The estimated random uncertainty of the results ranges from & 0.005 "C to frO.008 "C; the major uncertainties appear to lie in the determination of the volume of the gas bulb and the determination of its IPTS-68 temperature. The present results differ noticeably from earlier gasthermometric determinations in the range of temperature overlap. The value found for the thermodynamic temperature of the freezing point of A1 is (660.342f 0.01 5')"C.

Present Estimates of the Differences Between Thermodynamic Temperatures and the ITS-90

“…1), the more recent NBS/NIST gas thermometry results [7,31] are inconsistent with the earlier results [6]. Because of the continuity of the NBS/NIST program and because of the progressive discovery and mitigation of gas bulb-related problems, the most recently published results [7,31] must be regarded as superseding earlier results [6].…”

“…1), the more recent NBS/NIST gas thermometry results [7,31] are inconsistent with the earlier results [6]. Because of the continuity of the NBS/NIST program and because of the progressive discovery and mitigation of gas bulb-related problems, the most recently published results [7,31] must be regarded as superseding earlier results [6]. As the earlier data [6] below 505 K were acquired with apparatus and procedures similar to those that led to the inconsistent results at 505 K, the uncertainties claimed for the NBS/NIST gas thermometry results below 505 K are unreliable.…”

“…WG4 examined several effects that could have contributed to the difference. Astrov et al [8] Guildner & Edsinger [6] Edsinger & Schooley [7] Kemp et al [4] Quinn et al [24] Moldover et al [11] Strouse et al [13] Ewing & Trusler [10] Benedetto et al [14] Pitre et al [15] Ripple et al [12] (T68 -T90)…”

“…In his 1990 publication [31], Schooley reviewed the history and the results of CVGT at NBS/NIST that began in 1928 and concluded in 1990, with significant publications in the archival literature including [6] and [7]. Schooley's review shows that the NBS/NIST gas thermometer underwent several stages of improvements, particularly as problems were discovered when the thermometer was operated at the higher temperatures.…”

Review of temperature measurement

“…Examples of the utilization of constant volume gas thermometry are reported by Guildner and Edsinger, 7 by Berry, 9 Kemp et al 10 and in Refs. [13][14][15][16]. It is used to define the ITS-90 between 3 and 24.5561 K. 1 Corrections to account for the behavior of the measuring apparatus include ͑1͒ the dead space in connection tubes; 9 ͑2͒ thermal expansion of the gas bulb; 17,18 ͑3͒ the difference in density of the gas at different levels in the pressure sensing tubes; 9,17 ͑4͒ a thermomolecular pressure correction to account for temperature differences along the pressure sensing tube; 9,19,20 ͑5͒ the absorption of impurities in the gas.…”