Abstract. A vertical alumina palladium (Pd) freezing-point cell was made and used for the calibration of noble metal thermocouples. Various characteristics of the freezing process were investigated using type B thermocouples, and the best method of freezing is discussed. It was found that the freezing behaviour was influenced by the thermal history: it is preferable to freeze the Pd melt completely before carrying out the next test. The thermocouple emfs during freezing were determined by calculating the average emf during the first 10 minutes of the plateau just after the depression in the supercooling curve. This emf was reproducible within a standard deviation of 0.1 °C. The expanded uncertainty of calibrating a type B thermocouple in the Pd freezing-point cell was estimated to be 1.0 °C at the 95% confidence level (k = 2).

Print publication: Issue 5 (October 1999)