It might have emerged in any case; but Canning, with his brilliant popular gifts and his frank appeal to popular support, gave it a revivifying stimulus which it would never have received froman aristocrat of the type of Castlereagh.
Upon removing the material from the vessel and exposing it to the atmosphere the sulphide of iron undergoes a revivifying process, the oxygen of the air displacing the sulphur from the sulphide as free sulphur, and with moisture converting the iron into hydrated oxide of iron.