IRON. A ductile metal, susceptible of taking a high polish. By exposure to damp air, it absorbs oxygen, becoming rust. Its ores are very numerous. Few soils are destitute of some admixture. The ashes of plants are also furn ished with a small quantity. Cast iron con tains irnpurities, which are removed, to a great extent, in wrought iron. The former is brittle, harder, and lasts longer when exposed than wrought iron, which is ductile, soft, mallea.ble, and fibrous. Steel is a compound of carbon and iron, remarkable for its elasticity and hardness. Iron combines, also, with sulphur and halogen bodies. This is the black oxide, and exists in green vitriol and the proto-salts of iron, serving as a base. The peroxide is the common red or brown oxide; it is also a base, producing the persalts of iron. Iron is readily dissolved by acids, being firk oxidized, and then uniting with the acid. The salts of the protoxide are, for the most part, instable, changing to perox ides when exposed to moist air. Iron is dis
covered in solution by an infusion of gall-nuts, which, sooner or later, produce a black color (ink). If the color arises immediately, the per oxide is present; if the mixture requires stirring and exposure to air, the protoxide is present. Many of the compounds of iron are of interest to the farmer. The protosulphate (copperas) is much used in dyeing, in making ink, and as an emetic. It is added to urine and fluid manures, to fix their ammonia, which it converts into a sulphate. It is also powerfully disinfecting, removing bad smells. This body is sometimes present in marshy and peaty soils, and makes them barren; they are recovered by liming. The pyrolignate of iron (persalt) is used hi dye ing and the preservation of timber. The muriate has the same properties, and is also a medicine. Prussian Blue is a sesquiferrocyanide of iron.