Wollaston, Tennant and Berzelius identify new elements

Background. The identification of new elements occurred through chemical analysis of platinum ores and mineral samples. Wollaston's work on purifying platinum led to palladium and rhodium. Tennant analyzed insoluble residues from platinum ores, finding iridium and osmium. Berzelius and Hisinger discovered cerium in Bastnäs, Sweden, while Klaproth independently identified it in Germany.

Wollaston's Discoveries. William Hyde Wollaston discovered palladium in July 1802 and named it in August. He offered the material in a Soho shop in April 1803. Wollaston discovered rhodium soon after palladium; one account dates the rhodium discovery to 1803, while another dates it to 1804. He published the rhodium discovery in 1804 and disclosed palladium in 1805.

Tennant's Residues. Smithson Tennant analyzed insoluble residues from platinum ores in 1803. He identified iridium and osmium, naming osmium for its volatile oxide's smell. French chemists observed the black residue but lacked sufficient material. Tennant's larger sample allowed him to confirm two new elements, documented in a letter to the Royal Society on June 21, 1804.

Berzelius and Cerium. Jöns Jakob Berzelius, a Swedish chemist, discovered cerium in 1803 with Wilhelm Hisinger in Bastnäs. Berzelius worked as a physician near Stockholm before Hisinger provided him a laboratory. Martin Heinrich Klaproth independently discovered cerium in Germany in the same year. The ceria isolated contained other lanthanides, not pure cerium.