Thermochemistry of inorganic sulfur compounds III. The standard molar enthalpy of formation at 298.15 K of US1.992 (β-uranium disulfide) by fluorine bomb calorimetry☆☆☆

Abstract A thoroughly analyzed specimen of β-uranium disulfide of composition US 1.992±0.002 has been studied by fluorine-bomb calorimetry. The standard molar energy of combustion: Δ c U m o (US 1.992 , cr, β, 298.15 K) = −(4092.5±7.5) kJ·mol −1 has been determined on the basis of the reaction: US 1.992 (cr, β) + 8.976F 2 (g) = UF 6 (cr) + 1.992F 6 (g). The standard molar enthalpy of formation: Δ f H m o (US 1.992 , cr, β, 298.15 K) = −(519.7±8.0) kJ·mol −1 was derived, and from that result Δ f H m o (US 2 , cr, 298.15 K) = −(521±8) kJ·mol −1 is estimated.