Enthalpy increment of PbBi12O19(s) and ϕ-Pb5Bi8O17(s) by drop calorimetry

Enthalpy increments of PbBi₁₂O₁₉(s) and ϕ-Pb₅Bi₈O₁₇(s) were measured by drop calorimetry in the temperature range 463–895 K and 475–757 K, respectively. A Python-based computer program implementing the Shomate method was coded to fit the experimental data. The expressions for enthalpy increment of PbBi₁₂O₁₉(s) and ϕ-Pb₅Bi₈O₁₇(s) as a function of temperature are:

$H_T^0-H_{298}^0$ < PbBi₁₂O₁₉> (J/mol) = $180.994\times T+4939.217\times {10}^{-4}\times T^2-1746.59\times {10}^4\times T^{-1}-39289$ (T: 463 – 895 K)

$H_T^0-H_{298}^0$ < ϕ-Pb₅Bi₈O₁₇> (J/mol) = $792.256\times T-65.626\times {10}^{-4}\times T^2+1638.68\times {10}^4\times T^{-1}-290589$ (T: 475 – 757 K)

Entropies and Gibbs energy functions were also derived from the enthalpy increment data.