The 1962 He3 scale of temperatures. III. Evaluation and status

Abstract

In this third paper: the 1962 11e3 Scale of T emperatures is evaluated both as to its pre cision a nd its devi ation s from the thermodynamic K elvin Scale. Variou s ther modynamic quantities of If e3 con sistent with the 1962 11 e 3 Scale are derived and listed. The correct ion to a n observed vapor pressure for small amounts of 11e' is di scussed a nd tabulated . A descrip tion is given of the method of m llitiple variable least squares an alys is used for d eriving the final scale equ at ion and for re-analys is of isotherm dat a . F inally the present status of the 1962 IIe 3 Scale is discussed a long wit h som e con sideration s for the future. One factor in evaluating the 1962 H e 3 Scale is the fit of the input vapor-pressure data of Part I [46] to the Scale. Figure 1 and table 1 of Part II [6] show the deviations of the observed da ta from the final scale as T 62 (P 3) -T 5s(P 4)' The symbol T 62 is the temperature on t.he 1962 He 3 Scale corresponding to a He 3 vapor pressure, P 3, while T 58 is the tempera ture on the 1958 He 4 Scale [2] corresponding to the experimentally determined isothermal He 4 vapor pressure, P 4 • The standard deviation of the data from the scale is 0.25 mdeg and the maximum deviation over the full range is 0.6 mdeg. The data may not scat,ter completely randomly. For example, the data points just below 2 O K are all b elow the 1958 He 4 Scale and the point.s just above 2 O K are all above the 1958 He 4 Scale. H ence, if one wished to obtain the vapor pressure of H e 3 which is most probably isothermal with a given H e 4 vapor pressure, ;t slightly better value (in terms of consistency with the observed data) may be obtained by drawing a smooth curve through these data points or by using direct interpolation equations as discussed in Part I. However, the overall fit of the Scale to the inpu t data is very satisfactory in comparison with the errors of measurement of the two vapor pressures.I Much of the maierial in this paper III has been included ill a review chapter [52] on the development of ih e seale., IYork performed und er ihe auspices of t he U. S. Atomic Energy Commission . 567 Fit of the Experimental Thermodynamic Equation (ETE) ScaleBelow 0.9 O K the 1962 He 3 Scale was evaluated by examining its fit to the ETE Scale described in Part II. The ETE Scale is defined by a linear equation fitted to an empirical function, FX(P3,T), of H e 3 vapor pressure and temperature,As shown by the full line curve in figure 1 of P art II, temperatures calculated from eq (1) are in good agreement with the 1962 He 3 Scale; nowhere b elow 2 O K do the scales differ by more than 0.4 mdeg. the 1962 He 3 Scale, defined by eq (9b) of P art II, is therefore in effect an ETE scale from 0.2 to 2° and an empirical scale above 2 O K.The effect of possible errors in the various terms of the equation for the ETE scale, over the temperature range from 0.2 to 1.0 O K, should also be considered in evaluating the 1962 H e 3 Scale. The ETE scale was obtained from a least squares fit of the H e 3 -H e 4 vap...

Guidelines for realizing the International Temperature Scale of 1990 (ITS-90)

“…An apparatus for installing a graphite thermometer well and lid in a graphite crucible containing a molten metal sample 56 Figure 18. Differences between r 90 (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.…”

“…The relation between T 90 and t 90 is: t 9 o/°C = r 90 /K -273.15. (2) The ITS -90 extends upward from 0.65 K. There are alternative definitions of T 90 in certain temperature ranges and they have equal status.…”

“…The unit of the temperature r 90 is the kelvin, symbol K, and the unit of the temperature t 90 is the degree Celsius, symbol°C. The relation between T 90 and t 90 is: t 9 o/°C = r 90 /K -273.15.…”

“…The unit of the temperature r 90 is the kelvin, symbol K, and the unit of the temperature t 90 is the degree Celsius, symbol°C. The relation between T 90 and t 90 is: t 9 o/°C = r 90 /K -273.15. (2) The ITS -90 extends upward from 0.65 K. There are alternative definitions of T 90 in certain temperature ranges and they have equal status.…”

“…Differences between r 90 and T 68 (and t 90 (14) and (22) , and in the functions approximating them, given by equations (15) and (23) 15 A schematic representation of the ITS -90 showing the temperatures of the defining fixed points (or phase equilibrium states) on the scale and temperature ranges defined by interpolation instruments and equations ... Photograph of an all-plastic indium cell and its stainless steel container 46 Figure 13.…”