Discovery of lanthanum

Lanthanum was discovered in 1839 by the Swedish chemist Carl Gustaf Mosander in Stockholm. While studying cerium nitrate, he found that heating it and dissolving the product in dilute nitric acid left behind a new oxide as an impurity. He named the element from the Greek lanthanein, meaning to lie hidden, since it had been concealed within cerium compounds. Mosander went on to discover further rare earth elements: didymium, which was later shown to be a mixture, then erbium and terbium. The metal is soft, silvery and quickly tarnishes in air. Lanthanum is used in camera and telescope lenses to give glass a high refractive index, as a catalyst in oil refining and in the nickel-metal hydride batteries found in some hybrid cars.

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