Osmium

Category: transition metal Atomic number: 76 Colour: blueish-silver Melting point: 3,033°C (5,491°F) Boiling point: 5,012°C (9,054°F) First identified: 1803

Osmium was first identified in 1803 by the British chemist Smithson Tennant. Working with William Wollaston (see here), he melted crude platinum in aqua regia (a ferocious blend of acids used to melt metals) and it left a black residue. While Wollaston investigated the remaining platinum, Tennant experimented on this residue and discovered it could be separated out into two previously unknown metals: osmium and iridium. He was more impressed by iridium, naming osmium after the Greek word, osme, meaning smell, because it had a peculiar odour – several of its compounds also smell bad and the oxide is particularly unpleasant.

Depending on how you measure it, osmium is the densest element, about twice as dense as lead, but it has few contemporary commercial uses: only about 100 kilograms are currently produced each year. It is sometimes alloyed with iridium in expensive nibs for fountain pens, in surgical equipment, and in other tools that need be resistant to corrosion and wear. Osmium was one of the metals used in the filaments for lightbulbs, due to its high melting point, although tungsten came to be preferred for this purpose: the major German manufacturer of lighting equipment was named Osram in 1906 when both were in use – the name combines parts of the names of osmium and tungsten (bearing in mind that the German name for tungsten was still ‘wolfram’ at the time).