Melting and triple point temperatures of gallium as fixed points of the International Practical Temperature Scale

The liquid–solid (melting) and liquid–solid–vapor (triple point) phase equilibrium temperatures of pure gallium have been realized and studied as proposed secondary reference points of the International Practical Temperature Scale. The melt temperature is found to be 29.771 94 °C (302.921 94 K) and the triple point temperature 29.773 88 °C (302.923 88 K) for gallium 99.999 99% pure. The technique and apparatus for these realizations, suitable for the calibration of high‐precision thermometers, are described. These calibration points are finding important uses in medical, biological, ecological, and energy‐source thermometry.