Solubility of H2 and CO in molten alkali-metal nitrates

Abstract

The solubility of H₂ and CO often used as fuel gases in high-temperature fuel-cells has been studied in the molten equimolar mixture (sodium + potassium) nitrate at temperature values ranging between 500 and 600 K. In both cases the plots log(K_H/mol cm^–3 bar^–1) against K/T yielded straight lines whose least-squares equations are log K_H=–5.39–768 K/T and log K_H=–5.98–980 K/T for hydrogen and carbon monoxide respectively. The heats of solution and the standard entropies are calculated and compared with those of other systems. Both gases react slightly with the solvent, by H₂+ NO^–₃→ NO^–₂+ H₂O and CO + NO^–₃→ NO^–₂+ CO₂, which gave rise to “unusual” solubility kinetic curves. The experimental results are discussed in terms of the Uhlig–Blander theory.