Paul Émile (François) Lecoq de Boisbaudran (18 April 1838, Cognac, Charente – 28 May 1912) was a French chemist born in Cognac. In 1858 he joined the family winemaking business, but a year later was working as a chemist.
In 1874 he wrote Spectres lumineux: spectres prismatiques et en longueurs d'ondes destinés aux recherches de chimie minérale, which was published in Paris by Gauthier-Villars and was one of the first descriptions of the new science of spectroscopy developed by Kirchhoff. In 1875 he used this method to discover the element gallium, which he named after the Latin word for Gaul, Gallia. He found the metal in a sample of zinc ore from the Pyrenees. A year later he isolated the element by electrolysis. It was later claimed that Lecoq had named the element after himself, since gallus is the Latin translation of the French le coq, but Lecoq denied this in an article of 1877. The existence of gallium had been predicted in 1871 by Mendeleev, who called it eka-aluminium, and its discovery was a boost for Mendeleev's theory of the periodic table. Later Lecoq discovered samarium (1880) and dysprosium (1886). He also isolated gadolinium in 1885, which had been discovered in 1880 by J.C. Galissard de Marignac.
Lecoq contributed further to the development of the periodic classification of elements by proposing, soon after its discovery, that argon was a member of a new, previously unsuspected, group of elements, later to become known as the noble gases.
He died in Paris at the age of 74.
* Ramsay, W.; Sakurai, Joji; Orton, K. J. P.; Richards, Theodore W.; Reid, W. F.; Ling, Arthur R.; Dunn, J. T.; Collie, J. N. et al. (1913). "Obituary notices: Paul Émile (dit François) Lecoq de Boisbaudran, 1838-1912; Edward Divers, 1837-1912; Humphrey Owen Jones, F.R.S., 1878-1912; John William Mallet, 1832-1912; Henry de Mosenthal, 1850-1912; Benjamin Edward Reina Newlands, 1842-1912; John Pattinson, 1828-1912; Arthur Richardson, 1858-1912; John Wade, 1864-1912; William Ord Wootton, 1884-1912". Journal of the Chemical Society, Transactions 103: 742. doi:10.1039/CT9130300742.
He discovered dysprosium in 1886, but it was not used commercially until 1950.