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
Absolute zero their zero points at absolute zero by definition. It is commonly thought of as the lowest temperature possible, but it is not the lowest "enthalpy" state possible, because all real substances begin to depart from the ideal gas when cooled as they approach the change of state to liquid, and then to solid; and the sum of the enthalpy of vaporization (gas to liquid) and enthalpy of fusion (liquid to solid) exceeds the ideal gas's change in enthalpy to absolute zero. In the quantum-mechanical description, matter (solid) at absolute zero is in its ground state, the point of lowest internal