Abstract
The experimental work involved in setting up a temperature scale over the range 10-90° K which is accurate in terms of the thermodynamic scale is described. A constant volume helium gas thermometer is employed which has a metal diaphragm, separating the gas thermometer bulb from the mercury manometer, which permits the dead space volume to be determined with high precision. It is estimated that the thermodynamic scale is realized with an accuracy to ±0.01 degc. The boiling point of oxygen with a value of 90.18° K was used as the reference temperature; it was subsequently determined in absolute terms taking T0 = 273.15° K and the value obtained was 90.177 ± 0.006° K.
The scale has been recorded in terms of a group of eight capsule-type platinum resistance thermometers which can now be used as secondary standards. A comparison has been made with three other temperature scales established in the U.S.A. and U.S.S.R. and the overall range of the scales is shown to be within 0.02 degc when they are all based on the same value of the oxygen point.