Cadmium

Cadmium is a soft, bluish-white metal recovered as a byproduct of refining zinc, whose ores it always accompanies. Friedrich Stromeyer discovered it in 1817 while investigating impure zinc compounds.

For decades it was used in rechargeable nickel-cadmium batteries, in bright yellow, orange and red pigments, and in rust-resistant plating. It is toxic, however, and builds up in the body, so its use is now tightly limited; European rules restrict it in most electronics. Cadmium compounds are still used in some thin-film solar panels. Early quantum-dot televisions used tiny cadmium selenide crystals to make pure colors, though most makers have moved to cadmium-free versions.