Introduction

Abstract

Indium was discovered in 1863 by Ferdinand Reich and Hieronymus Theodor Richter at the Freiberg School of Mines, Saxony, Germany while they were studying zinc ore (sphalerite ore with traces of pyrite, arsenopyrite, galena, chalcopyrite, stannite) from the local Freiberg polymetallic vein-type deposit (‘Himmelfahrt Fundgrube’) for thallium (Fig. 1.1; Reich and Richter 1863a,b). The spectroscopy of unknown coatings led to the identification of characteristic indigo blue spectral lines instead of the thallium spectrum. The new element was named indium. Reich and Richter (1863a) noted: “... Es zeigte (sich) keine Thalliumlinie, dagegen eine indigoblaue bisher unbekannte Linie. 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” (“[...] It appeared no thallium line but an unknown indigo blue line. Following the preparation of small quantities of the material as chloride, hydroxide and metal, we got, after subtle moistening with hydrochlorine acid, a glancing, sharp and persistent blue line in the spectroscope. We concluded an unknown metal which we beg to inform you we want to call indium.”). Further analytical work led to the identification of sphalerite as the general mineral host for indium (Reich and Richter 1863b). Subsequent work on zinc flue dusts from 2.15 tons of zinc from the Freiberg ore deposit yielded about one kilogram of the pure metal. An ingot of 0.5 kilogram of this material was first exhibited during the world exhibition in Paris in 1867.