Thermochemistry of binary liquid gold alloys: The systems Au-Ni, Au-Co, Au-Fe, and Au-Mn

Abstract

In this paper we report enthalpy of mixing data for the liquid alloys of gold with manganese, iron, cobalt, and nickel obtained by a Calvet-type calorimeter at 1378 K. The enthalpies of mixing are compared with Gibbs energies calculated from earlier emf and vapor pressure studies to yield information on the excess entropies of mixing. The limiting enthalpies of solution of the liquid transition metals in liquid gold are compared with values predicted from the semi-empirical model of Miedemaet al. and with earlier data for the same transition metals in liquid copper. The calculated values of the excess entropy of solution in liquid gold are compared with the corresponding values in liquid copper near 1400 K. For Ni, Co, and Fe as solutes we observepositive shifts of 5 to 9 J K−1 mol−1 which are attributed to vibrational entropy terms. For Mn there is a strongnegative shift of about 35 J K−1 mol−1. This shift probably is due to “complex” or “associate” formation between gold and manganese atoms.