Vaporization behavior of Agp 2(s) and Au 2P 3(s)

Abstract

The vaporization behavior of AgP 2(s) and Au 2P 3(s) has been studied by mass loss effusion, from graphite and glass cells, in the respective temperature ranges 521 – 639 K and 646 – 773 K. The vaporization of Au 2P 3 is severely retarded, while that of AgP 2 is retarded somewhat less. Equilibrium pressures of P 4 obtained in both systems, when combined with other pressure data from the literature, lead to: 2AgP 2(s) = 2Ag(s) + P 4(g), ΔH° 600 = 33.1 ± 2.0 kcal ΔS° 600 = 40.0 ± 2.4 cal deg −1 4 3 Au 2 P 3( s) = 8 3 Au( s) + P 4( g) , ΔH° 740 = 44.3 ± 2.0 kcal ΔS° 740 = 45.6± 2.4 cal deg −1. Combination of these data with the published enthalpy of formation of P 4(g) and estimated heat capacities gives the following enthalpies of formation at 298.15 K: AgP 2(s), −1.8 ± 1.2 kcal mole −1, and Au 2P 3(s), −11.6 ±2.0 kcal mole −1 (relative to red phosphorus as the standard state).