REALIZATION OF THE ITS-90 AT IMGC IN THE RANGE OF LONG STEM PRTS

IMGC has established the fixed points required by the International Te mperature Scale of 1990 (ITS-90) for long-stem platinum resistance the rmometers (PRTs) at the highest accuracy level. The present paper desc ribes the fixed point apparatus and the measuring procedures used at I MGC for the accurate realization of each fixed point, and gives some d ata on the typical phase transitions thereby obtained. Moreover, since IMGC has developed both traditional and sealed cells for the realizat ion of the freesing or melting points of metals, the different types o f cells and the procedure used for their construction and preparation are also supplied. Finally, the reproducibilities of the freezing poin ts of Sn, Zn, Al, and Ag were evaluated by means of several determinat iaons with one standard thermometer.