The Leiden scale (°L) was used to calibrate low-temperature indirect measurements in the early twentieth century, by providing conventional values (in
kelvin
The kelvin, symbol K, is the primary unit of temperature in the International System of Units (SI), used alongside its prefixed forms and the degree Celsius. It is named after the Belfast-born and University of Glasgow-based engineer and ...
s, then termed "degrees Kelvin") of
helium
Helium (from el, ἥλιος, helios, lit=sun) is a chemical element with the symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas and the first in the noble gas group in the periodic ta ...
vapour pressure
Vapor pressure (or vapour pressure in English-speaking countries other than the US; see spelling differences) or equilibrium vapor pressure is defined as the pressure exerted by a vapor in thermodynamic equilibrium with its condensed phase ...
. It was used below −183 °C, the starting point of the
International Temperature Scale
The International Temperature Scale of 1990 (ITS-90) is an equipment calibration standard specified by the International Committee of Weights and Measures (CIPM) for making measurements on the Kelvin and Celsius temperature scales. It is an approx ...
in the 1930s (Awbery 1934).
References
*
Berman, A.; Zemansky, M. W.; and Boorse, H. A.
''Normal and Superconducting Heat Capacities of Lanthanum''
Physical Review, Vol. 109, No. 1 (January 1958), pp. 70–76. Quote:
:"The 1955 Leiden scale13 was used to convert helium vapor pressures into temperatures ..(13) H. van Dijk and M. Durieux, in ''Progress in Low Temperature Physics II'', edited by C. J. Gorter (North-Holland Publishing Company, Amsterdam, 1957), p. 461. In the region of calibration the 1955 Leiden scale, ''T''L55, differs from the Clement scale, ''T''55E, by less than 0.004 deg." (emphasis added)
*Grebenkemper, C. J.; and Hagen, John P.
''The Dielectric Constant of Liquid Helium''
Physical Review, Vol. 80, No. 1 (October 1950), pp. 89–89. Quote:
: "The temperature scale used was the 1937 Leiden scale." (emphasis added)
*Awbery, J. H.
''Heat''
Rep. Prog. Phys. 1934, No. 1
pp. 161–197
. Quote:
: "It should be mentioned that below −183 °C, the Leiden workers do not entirely agree with some of the other cryogenic laboratories, but use a scale of their own, generally known as the Leiden scale." (emphasis added)
Obsolete units of measurement
Scales of temperature
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