Selenium

Uses

Selenium’s photoconductivity — its ability to conduct electricity much more readily when exposed to light — made it central to the technology behind early photocopiers and light-sensitive exposure meters, where a selenium-coated surface converts patterns of light into an electrical signal. It’s also used to decolorize glass by counteracting the greenish tint that iron impurities naturally give it, and, in higher concentrations, to produce a deep ruby-red glass and certain ceramic glazes.

In nutrition, selenium is an essential trace mineral that the body uses in antioxidant enzymes and thyroid-related processes, which is why small amounts appear in multivitamins and are naturally present in foods like Brazil nuts, seafood and grains. Selenium compounds are also used in some anti-dandruff shampoos and in agriculture as a soil supplement in regions where local soils are naturally deficient in it.

History

Selenium was discovered in 1817 by Swedish chemists Jöns Jacob Berzelius and Johan Gottlieb Gahn while they were investigating reddish sediment left behind during sulfuric acid production. Berzelius initially suspected the material was tellurium, an element discovered decades earlier, but careful analysis showed it was something new that simply behaved similarly. Because tellurium had been named after the Earth, using the Latin word tellus, Berzelius named the new element selenium after Selene, the Greek goddess of the moon, treating the pairing as a kind of chemical companionship between the two elements.