Osmium

Osmium is a group metals with the symbol Os and atomic number 76.Osmium was first discovered in 1803 by Smithson Tennant in the residue left when crude platinum was dissolved by aqua regia (a mixture of hydrochloric acid and nitric acid). Application of Osmium is Osmium alloys such as osmiridium are very hard and, along with other platinum group metals, are used in the tips of fountain pens, instrument pivots, and electrical contacts, as they can resist wear from frequent operation.