A 40-gram ingot of indium
10 November 2023
Indium is a silvery-white, highly ductile, and very soft metal. It has atomic number 49 and the symbol In. It is primarily produced as a by-product of mining and processing other ores, notably zinc, and it has a variety of commercial uses.
Indium was discovered by chemists Ferdinand Reich and Hieronymous Theodor Richter in 1863. The element was discovered through its spectrographic signature, which contained a distinct, bright blue line. (Reich, who was color blind, had employed Richter as a lab assistant because he could read a spectrograph.) Because of the color of the line, the pair named the element after indigo. The notice announcing the discovery reads, in part:
Nachdem es gelungen war, den vermutheten Stoff, wenn auch bisher nur in äusserst geringen Mengen, theils als Chlorid, theils als Oxydhydrat, theils als Metall darzustellen, erhielten wir, nach Befinden nach dem Anfeuchten mit Chlorwasserstoffsäure, im Spectroskop die blaue Linie so glänzend, scharf und ausdauernd, dass wir aus ihr auf ein bisher unbekanntes Metall, das wir Indium nennen möchten, zu schliessen nicht anstehen.
(After we had succeeded in representing the suspected substance, even if so far only in extremely small quantities, partly as a chloride, partly as an oxide hydrate, partly as a metal, we found that after moistening it with hydrochloric acid, the blue line was so shiny in the spectroscope, sharp and persistent, so that we cannot hesitate to conclude from it that there is a previously unknown metal that we would like to call Indium.)
Subsequent analysis of indium’s spectrograph revealed there were actually two blue lines, one weaker than the other. The following year, Richter succeeding in isolating a sample of the metal, and their partnership ended acrimoniously after Richter claimed to be its sole discoverer. Whether this was a case of Richter trying to grab more credit than was due him or an example of the age-old story of a senior scholar taking credit for a grad student’s work has been lost in the mists of time.
Sources:
Miśkowiec, Pawel. “Name Game: The Naming History of the Chemical Elements: Part 2—Turbulent Nineteenth Century.” Foundations of Chemistry, 8 December 2022. DOI: 10.1007/s10698-022-09451-w.
Oxford English Dictionary, second edition, 1989, s.v. indium, n.
Reich, F. and Richter, Th. “Vorläufige Notiz über ein neues Metall.” Journal für Praktische Chemie, 89, 1863, 441–48 at 442. HathiTrust Digital Archive.
Weeks, Mary Elvira. “The Discovery of the Elements. XIII. Some Spectroscopic Discoveries.” Journal of Chemical Education, 9.8, August 1932, 1413–34 at 1429–32. DOI: 10.1021/ed009p1413.
Photo credit: Chemical Elements: A Virtual Museum, 2009. Wikimedia Commons. Licensed under a Creative Commons Attribution 3.0 Unported License.