THERMODYNAMIC PROPERTIES OF HIGH-TEMPERATURE AQUEOUS SOLUTIONS .X. ELECTRODE POTENTIALS OF SULFATE ION ELECTRODES FROM 0 DEGREES TO 100 DEGREES . ACTIVITY COEFFICIENTS AND ENTROPY OF AQUEOUS SULFURIC ACID

The potentials previously reported for the Pt-H2 | H2SO4(m) | PbSO4-PbO2-Pt and Pt-H2 | H2SO4(m) | Hg2SO4-Hg cells between 0 and55° have been reexamined using the recently experimentally determined partial molal heat capacities of sulfuric acid. By a third-law analysis, it was possible to demonstrate that most of the reported standard potentials cannot be correct over part or all of the 55° temperature range. By adopting the most recent value of E° and activity coefficients at 25° from one of the se s of data for the mercury cell, it was possible to derive a consistent set of E° values and activity coefficients for sulfuric acid and for the other cells over the entire temperature range. The thermodynamic data so obtained are in agreement with the best calorimetric data and vapor pressure measurements for sulfuric acid solutions.