Standard Reference Material 1745: Indium Freezing-Point Standard and Standard Reference Material 2232: Indium DSC Melting-Point Standard
Gregory F. Strouse
The freezing point of indium (156.5985 degrees C) is a defining fixed point of the International Temperature Scale of 1990 (ITS-90). Realization of this freezing point is performed using a fixed-point cell containing high-purity (greater than or equal to 99.999 % pure) indium. A single lot of indium (greater than or equal to 99.999 % pure) constituting Standard Reference Material (R) (SRM) 1745 and SRM 2232 has been evaluated, and certified as suitable for use in the realization of the freezing-point temperature of indium for the ITS-90. Based on results obtained with two fixed-point cells containing random samples of SRM 1745 and one fixed-point cell containing random samples of SRM 2232, the expanded uncertainty (k = 2) assigned to the freezing-point temperature of the metal is 0.34 m degrees C. In this document, the methods used for the fabrication of the indium freezing-point cells and for the evaluation of SRM 1745 and SRM 2232 are described.
indium, SRM, SRM 1745, SRM 2232, Standard Reference Material
Standard Reference Material 1745: Indium Freezing-Point Standard and Standard Reference Material 2232: Indium DSC Melting-Point Standard, Special Publication (NIST SP), National Institute of Standards and Technology, Gaithersburg, MD
(Accessed June 6, 2023)