THE PHASE BOUNDARIES OF WUSTITE

According to Darken and Gurry and to Swaroop and Wagner, the iron/wuestite phase boundary shows a minimum in oxygen content. From general thermodynamic relations it follows that at this minimum, the enthalpy of solution and entropy of solution of metallic iron in wuestite must be zero. With this condition and the application of further thermochemical data for wuestite, an equation for the Gibbs energy has been derived which may be used to calculate iron/wuestite and wuestite/magnetite phase boundaries in agreement with those determined experimentally.