Leiden scale to be true. Oxygen under a standard atmosphere boils at a temperature in the 90.15 to 90.18 K range. For hydrogen, it depends on the molecular variety. The boiling point is 20.390 K for "normal" hydrogen (made up of 75% orthohydrogen and 25% parahydrogen) and 20.268 K for pure parahydrogen. Under the purported definition, absolute zero would lie at -20.15 °L. Leiden scale The Leiden scale (°L) was used to calibrate low-temperature indirect measurements in the early twentieth century, by providing conventional values (in kelvins, then termed "degrees Kelvin") of helium vapour pressure. It was used below -183°C, the starting
Scale of temperature of matter. Temperature is a universal attribute of matter, yet empirical scales map a narrow range onto a scale that is known to have a useful functional form for a particular application. Thus, their range is limited. The working material only exists in a form under certain circumstances, beyond which it no longer can serve as a scale. For example, mercury freezes below 234.32 K, so temperature lower than that cannot be measured in a scale based on mercury. Even ITS-90, which interpolates among different ranges of temperature, has only a range of 0.65 K to approximately 1358 K (−272.5