SRM Metals

ITS-90 Metals

The six metals that define the ITS-90 from –38.8334 °C to 962 °C were certified as fixed-point standard SRMs. For each of the SRMs, a single lot of 20 kg to 24 kg of high-purity metal (>99.9999% pure) was purchased. The metals are packaged in protective containers that were either filled with argon or vacuum sealed. These SRMs were developed for the fabrication of freezing-point cells of the ITS-90 defining fixed points and for their use in the calibration of (HT)SPRTs and other thermometers requiring high-accuracy calibrations.

ITS-90 Freezing-Point Standard Metals

SRM #	Description	t, °C	Purity, %	Unit Form	Unit Size, g	U (k=2), mK	Unit Cost*,$
743	Hg TP	-38.8334	99.999 998	ampoule	680	0.14	216
1751	Ga MP	29.7646	99.999 995	ingot	200	0.04	call
1745	In FP	156.5985	99.999 99	10 g ingot	200	0.4	1001
741a	Sn FP	231.928	99.999 97	1 g shot	200	0.5	call
740a	Zn FP	419.527	99.999 947	1 g shot	200	0.7	348
1744	Al FP	660.323	99.999 96	1 g button	200	0.7	604
1746	Ag FP	961.78	99.999 974	1 g shot	300	1.1	1538

MP = melting point
FP = freezing point
TP = triple point

*PRICES ARE SUBJECT TO CHANGE WITHOUT NOTICE

Technical contact: gregory.strouse@nist.gov

Some of the ITS-90 FP standard metals

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Last Updated on: 2/25/04