Comparisons of some NIST fixed-point cells with similar cells of other standards laboratories

In this paper we present results of international comparisons of fixed-point cells of some of the defining fixed-point materials of the International Temperature Scale of 1990, These comparisons involved cells from seven national laboratories, although in some cases only one type of fixed-point material was compared, Except for silver cells, the agreement among cells of the same defining fixed-point material from the various laboratories was to within 1 mK. The expanded uncertainties (k = 2) of the comparison measurements were 12 mu K for Ga, 18 mu K for H2O, 27 mu K for Sn, 35 mu K for In, 37 mu K for Zn, 42 mu K for Al, and 55 mu K for Ag.