THERMODYNAMICS OF NICKEL-TIN LIQUID ALLOYS

An automated very high temperature calorimeter has been used to invest igate the partial and integral enthalpies of mixing of liquid nickel+t in alloys in the temperature and molar fraction range 867<T/K<1579 and 0<x(Ni)<0.80 respectively. The enthalpies of mixing, Delta(mix)H degr ees(m) = f(x(Ni)) are exothermic over the entire concentration range. They are represented by the following equation for temperatures betwee n 1530 and 1580 K: Delta(mix)H degrees(m)/kJ mol(-1) = x(1 - x)(-46.01 - 6.788x - 209.616x(2) + 203.879x(3) - 20.145x(4)) where x = x(Ni). T he coordinates of the minimum are Delta(mix)H degrees(m) = - 20.2+/-0. 6 kJ mol(-1) at x(Ni) = 0.60. The limiting partial molar enthalpy of N i in liquid tin, referred to liquid Ni, was determined to be h degrees (m)(Ni(1), in infinity Sn-(1)/kJ mol(-1) = - 36.48 - 12960/T over the entire temperature range scanned. The change in Fermi enthalpy on allo ying indicates a restricted number of electrons transferred from Sn to Ni for alloys with x(Sn) >0.75. Higher tin concentrations do not chan ge the number of electrons accepted by Ni.