Thermodynamic properties of the vapor transport reactions in the Au?Cl system by a transpiration-mass spectrometric technique

A new transpiration-mass spectrometric technique is described for the study of vapor transport reactions, whereby the vapor transport species can be identified and their partial pressures determined from mass spectrometer ion intensity data. The vapor transport species in the Au?Cl system at low temperature (T<450°C) has been identified as Au₂Cl_8(g). For the reaction $$2Au_{(c)} + 3Cl_{2(g)} = Au_2 Cl_{6(g)} $$ the following results were obtained $$\Delta G_R^\circ = - 24,600( \pm 4400) + 59.8( \pm 8.2) T; \pm 1200 cal$$ A vapor pressure diagram for the Au?Cl system has been constructed from the experimental results and selected data from the literature. A new vapor transport species Au FeCl_8(g) was identified when chlorine was passed over a mixture of iron and gold. Formation of the vapor complex gives rise to increased transport rates.