Abstract
The triple point of oxygen is realized by using the adiabatic calorimetric technique with an open cell and four samples including three different sources. The molar impurity concentrations of the samples and the triple point values of ideally pure oxygen are estimated from the relations between the melting temperature and the inverse of fraction of melt by a thermal analytical method. The estimated triple point values of the samples are agreed within the measurement uncertainty of ±0.035mK (one standard deviation level). The values are pointed out to be about 1.25mK lower than the triple point of the sealed cell, NRLM-7801, which is one of the transfer cells of the international intercomparison organized by the Consultative Committee of Thermometry.
