A thermodynamic study of the gaseous thorium carbides, ThC, ThC2, ThC3, ThC4, ThC5, and ThC6

Abstract

Six gaseous carbides of thorium, ThC_n(n=1–6), have been identified in a Knudsen effusion mass spectrometric investigation of the vapor phase above a thorium–uranium–rhodium–graphite system at high temperatures. The partial pressures of the thorium containing species were measured as a function of temperature in the 2300–2700 °K range. Third law enthalpies for the reactions Th(g)+nC(graphite) =ThC_n, n=1 to 6, and of various other homogeneous and heterogeneous reactions were evaluated. By combining the experimental enthalpies with appropriate thermodynamic data taken from literature, the following values for the atomization energies ΔH °_at,298, and standard heats of formation ΔH^°_f,298 of thorium carbides have been derived: