The decarbonation and heat capacity of ZnCO3

The decarbonation curve for ZnCO₃ has been determined in the pressure range 3–20 kbar by using a combination of cold-seal vessels and piston-cylinder apparatus with NaCl assemblies. Heat capacities for both synthetic and natural ZnCO₃ samples were measured by differential scanning calorimetry at temperatures ranging from 340 to 497 K. The results of these experiments indicate that the enthalpy of formation for smithsonite, ΔH_f(1,298.15), is approximately −817. kJ/mol. which is about 4 kJ more negative than most tabulated values.