Mass spectrometric determination and thermodynamic calculation of the equilibria between iron, carbon and oxygen

The reduction of iron ore to iron is one of the oldest chemical techniques. It marked the start of a new era in the prehistory of mankind: the iron age. Nowadays it is the second-largest human generated chemical process on earth. It amounts to quantities of the order of 2 million tons per day and is surpassed only by the burning of coal for the generation of heat. An enormous body of scientific literature exists on this process dealing with technical and chemical aspects. However, a complete survey, which could be used to comprehend all measurements, does not exist. Thermodynamics however, enables one to calculate the equilibrium between a number of chemical compounds in an entire temperature and pressure region, if only a limited set of data, e.g. free energy and entropy, of these compounds are known. The latter data should be provided by other means. Among others, mass spectrometric determination of some equilibria between these compounds can provide the desired data. We will give the necessary thermodynamic formulae, derived from fundamental principles. A relatively small number of mass spectrometic measurements will give the complete set of equilibria between iron, iron oxides, iron carbonate graphite (carbon) or cementite (Fe3C), and a CO-CO2 mixture.