Discovered in 1803 by Smithson Tennant (most famous for his determination that diamond is just a form of carbon), osmium is a very dense, blue-white hard metal. Its name is taken from the Greek, osme, for "odor". The oxides of osmium emit highly toxic gases and form readily when the metal is exposed to air. Thus there are few commercial applications for osmium except as a minor alloying agent where it reduces frictional wear ("osmiroid" ball point pen tips, for example).
Most osmium is recovered as a by-product of the refining of platinum and nickel ores.
Palladium is part of the the Platinum Group Metals (PGM) whic is located in the 5th and 6th rows of the transition metal section of the periodic table and includes Ruthenium, Rhodium, Palladium, Osmium, Iridium, and Platinum. Common characteristics include resistance to wear, oxidation, and corrosion, high melting points, and oxidation states of +2 to +4. They are generally non-toxic.
\(OsO_4\) (Osmium Tetroxide) is a valuable catalyst in organic chemistry reactions.
Stephen R. Marsden (ChemTopics)