Editing Platinum (section)

===Standard===
[[File:Platinum-Iridium meter bar.jpg|thumb|upright=1.2|right|Prototype International Meter bar made by [[Johnson Matthey]]]]
From 1889 to 1960, the [[metre|meter]] was defined as the length of a platinum-iridium (90:10) alloy bar, known as the [[History of the meter#International prototype metre|international prototype meter]]. The previous bar was made of platinum in 1799. Until May 2019, the [[kilogram]] was defined as the mass of the [[international prototype of the kilogram]], a cylinder of the same platinum-iridium alloy made in 1879.<ref name="meter">{{cite book|doi = 10.1007/978-3-642-00738-5_4|date = 2010|last1 = Gupta|first1 = S. V.| chapter=Metre Convention and Evolution of Base Units |page = 47 |title=Units of Measurement |volume = 122|series = Springer Series in Materials Science|isbn = 978-3-642-00777-4| s2cid=150519250 }}</ref>

The Standard Platinum [[Resistance Thermometer]] (SPRT) is one of the four types of thermometers used to define the [[International Temperature Scale of 1990]] (ITS-90), the international calibration standard for temperature measurements. The resistance wire in the thermometer is made of pure platinum (NIST manufactured the wires from platinum bar stock with a chemical purity of 99.999% by weight).<ref name="bipm">{{cite web|title=Guide to the Realization of the ITS-90 - Platinum Resistance Thermometry|publisher=[[International Committee for Weights and Measures]]|url=https://www.bipm.org/utils/common/pdf/ITS-90/Guide-ITS-90-Platinum-Resistance-Thermometry.pdf|access-date=23 October 2020|archive-date=24 February 2021|archive-url=https://web.archive.org/web/20210224094446/https://www.bipm.org/utils/common/pdf/ITS-90/Guide-ITS-90-Platinum-Resistance-Thermometry.pdf|url-status=dead}}</ref><ref name="nist">{{cite web|title=Standard Reference Material 1750:Standard Platinum Resistance Thermometers,13.8033 K to 429.7485 K|publisher=[[NIST]]|url=https://www.nist.gov/system/files/documents/srm/SP260-139.PDF}}</ref> In addition to laboratory uses, Platinum Resistance Thermometry (PRT) also has many industrial applications, industrial standards include ASTM E1137 and IEC 60751.

The [[standard hydrogen electrode]] also uses a [[platinized]] platinum electrode due to its corrosion resistance, and other attributes.<ref name="HollemanAF">{{cite journal|last1 = Feltham|first1 = A. M.|last2 = Spiro|first2 = Michael|title = Platinized platinum electrodes|journal = Chemical Reviews|volume = 71|pages = 177–193|date = 1971|doi = 10.1021/cr60270a002|issue = 2}}</ref>