S. R. Dharwadkar

Thermodynamic investigation of the vaporization of molybdenum trioxide

Abstract The vapour pressure of MoO3(s) was measured using a novel thermogravimetric system. The total pressures obtained in this investigation agree well with the best assessed values from data in the literature. The enthalpy of sublimation at 1000 K obtained from this work is 365.2 ± 5.0 kJ mol−1 in close agreement with the assessed value of 369.1 ± 0.8 kJ mol−1. The vapour pressure data for pure MoO3(s) was obtained in the context of our investigations on the vaporization of transition metal molybdates.

The palladium-platinum phase diagram

Abstract The palladium-platinum equilibrium phase diagram was determined using a “spot” technique. The two metals form a series of solid solutions over the entire composition range, which solid solutions coexist with their liquid solutions. The experimentally observed gap between the solidus and the liquidus was comparable to that calculated employing a regular solution model. The phase boundaries delineated in the present work, however, differ significantly from those in an earlier work which were obtained by the Pirani method.

The standard molar enthalpy of formation of ZrTe3O8

Abstract The molar enthalpies of solution of ZrTe 3 O 8 , TeO 2 , and ZrF 4 , in HF(aq) of concentration 10 mol.dm −3 have been measured using an isoperibol calorimeter. From the results and other auxiliary quantities, the standard molar enthalpy of formation of ZrTe 3 O 8 (s) has been determined to be Δ f H m °(298.15 K) = −(2119.2 ± 9.6)kJ·mol −1 .

The standard molar enthalpy of formation of HfTe3O8

Abstract The molar enthalpies of solution of HfTe 3 O 8 , TeO 2 and HfF 4 in 10 mol dm −3 HF(aq) have been measured using an isoperibol-type calorimeter. From these results and other auxiliary data, the standard molar enthalpy of formation of HfTe 3 O 8 (s) has been calculated to be Δ f H m 0 (298.15 K) = −2129.1 ± 10.1 kJ mol −1 . This value of enthalpy of formation of HfTe 3 O 8 is consistent with the free energy of formation of HfTe 3 O 8 determined in this laboratory by the transpiration technique.

The standard molar enthalpy of formation of HfMo2O8

The molar enthalpies of solution of HfMo2O8, Mo and HfF4 in (10 mol HF(aq) + 4.41 mol H2O2(aq)) dm−3 have been measured using an isoperibol type calorimeter. From these results and other auxiliary data, the standard molar enthalpy of formation of HfMo2O8(S) has been calculated to be ΔfHm(298.15K) = −2605.8 ± 5.9kJ mol−1. This value of enthalphy of formation of HfMo2O8 is consistent with the second law enthalpy of formation of HfMo2O8 determined in this laboratory by transpiration technique.