In 1803, Smithson Tennant analyzed the insoluble residue and concluded that it must contain a new metal. Vauquelin treated the powder alternately with alkali and acids and obtained a volatile new oxide, which he believed was of this new metal—which he named "ptene", from the Greek word (ptènos) for winged. However, Tennant, who had the advantage of a much larger amount of residue, continued his research and identified two previously undiscovered elements in the black residue, iridium and osmium. He obtained a yellow solution (probably of "cis"–[Os(OH)2O4]2−) by reactions with sodium hydroxide at red heat. After acidification he was able to distill the formed OsO4. He named it osmium after Greek "osme" meaning "a smell", because of the ashy and smoky smell of the volatile osmium tetroxide. Discovery of the new elements was documented in a letter to the Royal Society on June 21, 1804.