T. A. Stolyarova

Standard thermodynamic properties of Pd and Pt ditellurides

Platinumgroup elements (PGE) are transition metals of group VIII in the periodic table of chemical elements. Although similarities between PGE are emphasized in geochemistry, the types of their interac� tions with other elements and the specifics of their electron structure make it possible to classify PGE into three groups. Groups 1 and 2 include Ru with Os and Ir with Rh, respectively, and group 3 consists of Pt and Pd, which are the most chemically active PGE (this applies, first of all, to Pd) because of the structure of their electron shells. The most widely spread natu� rally occurring PGE tellurides are those of Pt and Pd, which usually contain Bi, and no pure binary com� pounds have ever been found. Pd and Pt ditellurides are typically contained in ores at Cu-Ni mineral deposits. An important problem is revealing the factors responsible for the different behavior of Pt and Pd in mineralforming processes, an issue that cannot be elucidated without knowing properties of the most widely spread minerals at these deposits. Our research was focused on the calorimetric determination of the enthalpy of formation of Pt and Pd ditellurides, with the use of literature data on lowtemperature adiabatic calorimetry and electrochemical measurements. Pt and Pd ditellurides can be easily synthesized by heating corresponding stoichiometric mixtures in ampoules of quartz glass evacuated to

Determination of the enthalpies of formation of some platinum antimonides and their phase diagrams under standard conditions

Using the method of direct synthesis calorimetry, we determined the standard enthalpy of formation of PtSb (stumpflite), ΔfH°298.15 (PtSb, cr) =–105.16 ± 0.84 kJ/mol and PdSb2 (geversite), ΔfH°298.15 (PtSb2,cr) =–160.92 ± 0.84 kJ/mol. Isothermal (298.15 K, p = 1 bar) phase diagrams were computed for the Pt–Sb–S and Pt–Sb–O ternary systems in the coordinates composition of the Pt–Sb binary system versus fugacity of a gaseous volatile component (O2, S2).

Calorimetric determination of the standard enthalpy of formation of stannite, Cu 2 FeSnS 4

The standard enthalpy of formation of stannite (Cu2FeSnS4) was calculated from the calorimetric measurements of the reactions of its formation from simple synthetic sulfides: Cu2S + FeS2 + SnS → Cu2FeSnS4 and 2CuS + FeS + SnS → Cu2FeSnS4. Using published data for the binary sulfides, the standard enthalpy of formation of stannite from the elements was determined as ΔfH°298.15(Cu2FeSnS4) =–(417.28 ± 2.28) kJ mol–1.