Indium is a soft, ductile, manleable, lustrous metallic metal. It is is a chemical element with the symbol In and atomic number 49. It’s colour is silvery white and it has a face-centered tetragonal structure. It is liquid over a wide range of temperatures, like gallium that belongs to its same group. Both indium and gallium are able to wet glass. Indium is stable in air and in water but dissolves in acids. When heated above its melting point it ignites burning with a violet flame.
It was discovered in 1863 by Ferdinand Reich and Hieronymous Theodor Richter by spectroscopic methods. They named it for the indigo blue line in its spectrum. Indium was isolated the next year. Indium is a minor component in zinc sulfide ores and is produced as a byproduct of zinc refinement. It has no biological role, though its compounds are toxic when injected into the bloodstream. Most occupational exposure is through ingestion, from which indium compounds are not absorbed well, and inhalation, from which they are moderately absorbed.
- Used in the manufacturing of automobile bearings, which improves anti-seizure properties and moisture resistance.
- Used in semiconductor industries in the manufacturing of transistors, rectifiers, and diodes.
- Used in plating applications.
- Used in manufacturing of corrosive resistant mirrors.
Physical Properties of Indium
- It is a silvery-white, highly ductile post-transition metal with a bright luster. It is so soft that like sodium, it can be cut with a knife. It also leaves a visible line on paper.
- It is a member of group 13 on the periodic table and its properties are mostly intermediate between its vertical neighbours gallium and thallium. Like tin, a high-pitched cry is heard when indium is bent a crackling sound due to crystal twinning.
- Like gallium, indium is able to wet glass. Like both, indium has a low melting point, 156.60 °C, higher than its lighter homologue, gallium, but lower than its heavier homologue, thallium, and lower than tin.
- The boiling point is 2072 °C, higher than that of thallium, but lower than gallium, conversely to the general trend of melting points, but similarly to the trends down the other post-transition metal groups because of the weakness of the metallic bonding with few electrons delocalized.