Isotope exchange of iodine in iodide-iodate melts studied by radio paper chromatography

The isotopic exchange reaction of iodine in fused NaI–NaIO₃ and KI–KIO₃ systems, which does not proceed until the mixture is melted, is found to be almost instantaneous in homogeneous melts. The equilibrium is attained within a period of less than 5 min at a temperature 5°C above the melting temperature of each composition for both systems. No noticeable exchange is observed even after heating the samples for 30 min at a temperature 20°C below the corresponding melting point. A single-step bimolecular association-dissociation mechanism is proposed for the exchange.