Part 3 - Wollaston’s Contribution
Palladium was finally isolated from platinum and identified as a separate elemental metal in 1803 by William Hyde Wollaston, a brilliant researcher who made many contributions to science. Wollaston made important discoveries in astronomy (the dark lines in the solar spectrum, a crucial tool in stellar astronomy today), biochemistry (he discovered cystine, the first amino acid), physiology (he was the first to postulate that human hearing is limited to certain frequencies), and physics (in atomic theory and crystallography).
 The Wollaston Medal is named after him: the highest award granted by the Geological Society of London, first granted in 1832. (It was originally made of palladium.) He even had an island in the Arctic named after him, in recognition of a navigational instrument he invented.
Wollaston had formed an association with Smithson Tennant to conduct experiments in chemistry. As the 19th century dawned, that platina is dissolved in aqua regia was well known, with an insoluble black residue remaining. The partners decided between them that Wollaston would investigate the soluble portion and that Tennant would examine the insoluble residue. Wollaston then was able to separate out palladium in 1802 and rhodium in 1804. Tennant announced his discoveries of indium and osmium in 1804.
Wollaston’s process began with with platina - a natively occuring platinum mix which came from South America. To refine it, the common practice was to dissolve it in aqua regia (a mixture of hydrochloric and nitric acids). Adding ammonium chloride would then cause the platinum to precipitate out of solution in the form of an insoluble complex salt. Wollaston went further, adding iron, and treating the precipitate again with aqua regia. Adding iron a second time, he obtained a new precipitate, different than the previous ones.
When he treated this new precipitate with nitric acid, he obtained a reddish solution. This readily combined with mercury into an amalgam that when decomposed by heat left a new white metal.
 Wollaston initially named his discovery “ceresium,” after the newly-discovered asteroid Ceres. But he soon changed it to palladium, after a different new asteroid: Pallas, which in turn was named after the Greek Goddess of wisdom.
Wollaston didn’t announce his discovery; he apparently thought it would have commercial value, and didn’t want to tell others how to make it. In April 1803, he anonymously printed notices of palladium’s properties, and made it available for sale in a Soho shop.
Other scientists were skeptical, especially chemist Richard Chenevix. He believed that palladium was a fraud; he suspected it was only an alloy of platinum, and not a new metal at all. Chenevix even claimed to have created his own palladium by combining mercuric oxide, platinum, aqua regina, and ferrous sulfate.
Wollaston rebutted Chevenix’s claims, anonymously offering a reward of twenty pounds to anybody who could synthesize palladium. After many failures, chemists finally accepted palladium as a new metal.
Wollaston finally went public with his discovery in February of 1805. His secrecy over palladium put him into disfavor with scientists of the day who favored open communication to further scientific progress. Nonetheless, the importance of his contributions were recognized; the prestigious Royal Medal from the Royal Society was awarded to him for solving the riddle of malleable platinum. He made and sold the metal for years but refused to reveal the process until shortly before his death in 1826.
Continued from Part 2
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