Abstract
Relative enthalpies of cubr from 298.15 to 1,301 k were measured at the Bureau of Mines to provide thermodynamic data needed for the advancement of mineral technology. The temperatures of transition were meaured by differential scanning calorimetry and the standard enthalpies of transition (ahtr deg) by drop calorimetry. The combined results gave reversible transitions at 657 k with ahtr deg = 1.10 Kcal/mol, at 741 k with ahtr deg = 0.51 Kcal/mol, and at 759 k with an enthalpy of fusion (ahm deg) of 1.22 Kcal/mol. An anomalous increase in heat capacity preceded the first crystal transition at 657 k. Tabulated values are listed for the standard relative enthalpy, heat capacity, entropy, and Gibbs energy function from 298.15 to 1,500 k. Standard relative enthalpies are also given in equation form and combined with thermodynamic data from the literature to derive values of standard enthalpies of formation and Gibbs energies of formation.
