Development at the Institut National de Métrologie of sealed cells as IPTS fixed points

Abstract

Several years ago, the Institut National de Métrologie (INM) began using sealed cells to determine the triple points, melting or freezing points of the International Practical Temperature Scale of 1968 (IPTS-68). Details have appeared in Bonnier and Malassis (1975), Bonnier and Hermier (1978 and 1980). The aim of this paper is to review the different INM cells and the method of using them. Reasons are given why some substances can be studied easily with a permanent flux of heat and why others can be studied only with a calorimetric method. The results will lead to an explanation of the differences between the designs of the cells. It should be recorded that part of the work described was performed at the National Institute of Metrology of Peking, China, by Messrs Ling Shin King and Wou Bi Jin.