2006 Volume 47 Issue 6 Pages 1555-1559
The thermodynamic properties of Zn8La were investigated by calorimetry. The standard entropy of formation at 298 K, ΔfS298°, was determined from measuring the heat capacities, Cp, from near absolute zero (2 K) to 300 K by the relaxation method. The standard enthalpy of formation at 298 K, ΔfH298°, was determined by solution calorimetry in hydrochloric acid solution. The standard Gibbs energy of formation at 298 K, ΔfG298°, was determined from these data. The results obtained were as follows: ΔfH298°(Zn8La)/kJ·mol−1 = −297.18±18; ΔfS298°(Zn8La)/J·mol−1·K−1 = −25.02±3.60; ΔfG298°(Zn8La)/kJ·mol−1 = −289.71±18. The coefficient, γ, of the electronic term contributing to the heat capacity of Zn8La was small, indicating that decrease of the density of states for 4f component of the lanthanum atom in the vicinity of EF.