萊頓溫標

萊頓標度 (°L) 在20世紀初通過提供氦蒸氣壓的常規值來校準低溫間接測量值。

萊頓標度可在-183°C以下使用，這也是1930年代國際溫標的起點（Awbery 1934）。

參考資料
Berman, A.; Zemansky, M. W.; and Boorse, H. A.; [http://prola.aps.org/abstract/PR/v109/i1/p70_1 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, TL55, differs from the Clement scale, T55E, by less than 0.004 deg. » (emphasis added)
Grebenkemper, C. J.; and Hagen, John P.; [http://prola.aps.org/abstract/PR/v80/i1/p89_1 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.; [http://ej.iop.org/links/rBN0TrIu4/oMvHcjH_2xGtgmnTav5vpA/rpv1i1p161.pdf Heat*], Rep. Prog. Phys. 1934, No. 1, [http://www.iop.org/EJ/abstract/0034-4885/1/1/308/ 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)