Indium: a metal that can be bitten through

Indium properties and areas of application


In­di­um is a fusible, spark­ly, sil­very-white met­al with a melt­ing point of 157°C (314°F).This tem­per­a­ture is one of the ref­er­ence points on the in­ter­na­tion­al tem­per­a­ture scale.

It is soft enough to cut with a knife or bend with your hands… or even bite through! If you bend a piece of in­di­um, you will hear a crunch – a tes­ta­ment to changes in the met­al’s crys­tal lat­tice. In­di­um ions tint flames in­di­go.

His­to­ry of dis­cov­ery

Ger­man sci­en­tists Fer­di­nand Re­ich and Jerome Richter dis­cov­ered in­di­um in 1863. Re­ich was study­ing a zinc ore, spha­lerite, hop­ing it would con­tain a sam­ple of the new­found el­e­ment thal­li­um. As Re­ich was col­or­blind, he asked his col­league Richter to check the spec­trum for him. The sci­en­tists were sur­prised: in­stead of the green line they were ex­pect­ing, Richter no­ticed a rich vi­o­let-blue line that had not been seen be­fore. Re­ich and Richter re­al­ized that they had found a new el­e­ment. They called it the Latin word in­dicum – "pur­ple" or "in­di­go." The sci­en­tists lat­er quar­reled over who dis­cov­ered this el­e­ment, with Richter claim­ing to be the sole dis­cov­er­er.

Richter con­tin­ued seek­ing this met­al. Three years lat­er, an in­di­um in­got weigh­ing 0.5 kg was demon­strat­ed at the Paris Uni­ver­sal Ex­po­si­tion.


Pure in­di­um met­al can be found in na­ture, but most of it is pro­duced as a byprod­uct when melt­ing zinc ore. Based on cur­rent con­sump­tion, sci­en­tists sug­gest that its sup­ply will meet hu­man needs for just the next 13 years.

Chem­i­cal prop­er­ties

When heat­ed, in­di­um re­acts with sul­fur, form­ing in­di­um (III) sul­fide:

2In + 3S = In­₂S₃

It dis­solves slow­ly in ni­tric acid, form­ing in­di­um (III) ni­trate:

In + 4H­NO₃ = In(NO₃)₃ + NO + 2H₂O

When in­di­um and gal­li­um touch, they dis­solve in each oth­er, form­ing an al­loy that melts at 16°C (61°F). Such al­loys are used to sub­sti­tute for mer­cury in de­vices like ther­mome­ters.


In­di­um is added to oth­er met­als to pro­duce strong, sol­id al­loys for den­tistry and electrics. It in­creas­es the wear re­sis­tance of parts – the ad­di­tion of in­di­um re­duces the co­ef­fi­cient of fric­tion. In­di­um is not very tox­ic and is not me­tab­o­lized by liv­ing or­gan­isms. How­ev­er, pro­longed res­pi­ra­tion of its salts or in­di­um ox­ide can lead to lung dis­ease, and in­ject­ing it neg­a­tive­ly af­fects the kid­neys. The ra­dioac­tive iso­tope In-111 emits gam­ma ra­di­a­tion. It is used in pre­cise med­i­cal scan­ners to rec­og­nize os­teomyeli­tis (bone dis­ease).

In­di­um first found sig­nif­i­cant use dur­ing World War II, where it was used to coat air­craft bear­ings. To­day, in­di­um tin ox­ide can be found in LCD-TVs, mon­i­tors, and smart­phone screens. It is a good elec­tri­cal con­duc­tor that can send sig­nals to in­di­vid­u­al pix­els of the screen with­out in­ter­fer­ing with the light from oth­er pix­els. Cop­per-in­di­um-gal­li­um se­lenide is used as a ma­te­ri­al for so­lar bat­ter­ies.