Oxides and Hydroxides.-Iron forms three oxides: ferrous oxide, FeO, ferric oxide, Fe2O3, and ferroso-ferric oxide, Fe304.
Rend., 1892, 114, p. 1429) obtained it by acting with nitrous oxide on metallic iron at 200°, and Tissandier by heating the metal to 900 in carbon dioxide; Donau (Monats., 1904, 25, p. 181), on the other hand, obtained a magnetic and crystalline-ferroso-ferric oxide at 1200°.
It forms red crystalline double salts with the chlorides of the metals of the alkalis and of the 1 By solution in concentrated hydrochloric acid, a yellow liquid is obtained, which on concentration over sulphuric acid gives yellow deliquescent crusts of ferroso-ferric chloride, Fe3C118H20.
With ferric salts its solution gives a deep blue colour, and with ferrous salts, after exposure to the air, an insoluble, blue-black, ferroso-ferric gallate.
It may be regarded as a ferroso-ferric oxide, FeO.Fe 2 O 3, or as iron ferrate, Fe"Fe 2 '0 4.