Manganese is a metal of a dull whitish colour, but soon changes to a dark grey by exposure to the air. It is hard, brittle, rough in its fracture; not pulverizable, but falls to powder when broken to pieces by spontaneous oxidation. It is so difficult of fusion, that no heat yet exhibited has caused it to run into masses of any considerable magnitude. Concentrated sulphuric acid attacks manganese, at the same time that hydrogen gas is disengaged. Nitric acid dissolves it with effervescence, and the escape of nitrous gas. A spongy, black, and friable matter remains, which is a carburet of iron. The oxide is more readily soluble in nitrous acid. Manganese is dissolved in the usual manner by muriatic acid. In the dry way, the oxide of manganese combines with such earths and saline substances as are capable of undergoing fusion in a strong heat Manganese melts readily with most of the other metals, but rejects mercury. Gold and iron are rendered more fusible by a due admixture of manganese, and the latter metal is rendered more ductile. Copper becomes less fusible, and is rendered whiter, but of a colour subject to tarnish. The ore of manganese, known in Derbyshire by the name of black wadd, is remarkable for its spontaneous inflammation when thoroughly dried with oil.