2293.     ---------------.  [MITTASCH, A.]  [Iron Carbonyl and Carbonyl Iron.]  Ztschr. angew. Chem., vol. 41, 1928, pp. 827-833; Chem. Abs., vol. 22, 1928, p. 4731.

        Fe pentacarbonyl is produced on a large scale by circulating CO under pressure over sponge Fe at 150°-200° and cooling the gases evolved.  It has d.₄²⁰ 1.453, a surface tension of 22 dynes per cm. and a viscosity of 0.0075 c.g.s. unit at 20°.  Its heat of formation (liquid) is 54.2 kcal., latent heat of fusion 3.25 kcal. per mol., and heat of combustion 384.5 kcal. per mol.  In alkaline solution it behaves as a powerful reducing and dechlorinating agent for organic compounds.  In pentane solution it combines with Br, forming a yellow unstable compound, which rapidly decomposes with evolution of CO and formation of the reddish-brown compound, Fe(CO)₄Br₂.  Iron pentacarbonyl decomposes at 250° in a hollow vessel heated by radiation, yielding a finely divided Fe containing about 1% C.  If this is melted in a vacuum high-frequency furnace together with the requisite quantity of pure FeO, obtained by combustion of the carbonyl, an exceedingly pure Fe of high permeability, low hysteresis, and small wattage loss is obtained.