Pure Iron Preparation
The pure metal is not often encountered in commerce, but is usually alloyed with carbon or other metals. Chemically pure iron can be prepared either by the reduction of pure iron oxide (best obtained for this purpose by heating the oxalate in air) with hydrogen, or by the electrolysis of aqueous solutions of iron(II)
salts, e.g., of iron(II) ammonium oxalate. On the technical scale, pure iron is prepared chiefly by the thermal decomposition of iron pentacarbonyl. The so-called “carbonyl iron” prepared in this way initially contains some carbon and o;o,,’Ygen in solid solution. These impurities can be removed by suitable after treatment.
Pure iron is a lustrous, rather soft metal (hardness 4.5). Some of its physical properties are given in Table 5.43. Iron is ferromagnetic, i.e., it is strongly magnetized “”hen placed in a magnetic field. Unlike iron which contains
carbon, pure iron has a very low remanence, i.e., it instantly loses its magnetization when the applied electric field is removed. For this reason it finds certain applications in electrotechnology, e.g., for electric motors and transformers, in which rapid fluctuations must occur in the magnetism of·an iron core.