About a first order transformation of magnetite at 1 160 {\deg}C

Abstract

In the literature on the w{\"u}stite/magnetite transformation, there are two distinct values of the enthalpy and entropy terms of the equilibrium between these two oxides. The formalism established previously for the calculation of thermodynamic properties of w{\"u}stite is taken as well as the adjustment of the boundary between the respective domains. A first-order transformation of the magnetite is demonstrated at 1 433 K or 1 160{\textdegree}C where the change in the reference enthalpy is -9 990 J.mole-1 at heating, with the corresponding entropy change being-6.89 J.K-1. . mole-1. The approximate determination of enthalpy vs temperature is made for both varieties of magnetite. Two values of the molar heat content are deduced, with which a direct experimental value can be compared.