Realization of the Triple Point of Indium in Sealed Glass Cell

Abstract

The triple point of indium was realized by sealed glass cells for the standard platinum resistance thermometry.
Three samples of pure indium (about 700g, respectively) from different sources were put into cylindrical glass cells (external diameter; 35mm, height; 200mm, inner diameter of the thermometer well; 11mm), which were sealed off after evacuating lower than 0.01Pa. The cell surrounded by a hollow block of aluminum was set in an electric furnace. The melting and freezing curves were obtained by three long stem-type Pt resistance thermometers which had been calibrated at the zinc point, the tin point and the triple point of water.
The estimated value of the triple point of indium from the melting and freezing plateaus gave 156.6296°C±0.0003°C on IPTS-68. The range of super-cooling in the freezing point experiment was as small as 1°C.