Ruthenium
a tetrad metallic element discovered by Osann in 1828, in the platinum ores from the Ural, and first isolated by Claus in 1845. Symbol, Ru.; at. wt., 101.7. It occurs chiefly in osmiridium, and is separated from the latter by heating to redness a mixture of this ore and common salt in a current of moist chlorine. By digestion in cold water an extract is obtained from which ammonia throws down the oxides of ruthenium and osmium. The latter is expelled by heat, and the former converted into ruthenate of potassium by fusion with potash, which yields oxide of ruthenium on addition of nitric acid.
On ignition in a stream of hydrogen the oxide is reduced to the metallic state in the form of porous fragments. With the exception of osmium it is the most refractory of all metals, but can be fused in the hottest part of the oxyhydrogen blowpipe. It then has a density of 11 to 11.4, and is scarcely attacked by nitro-muriatic acid.