THE REACTION OF POTASSIUM-IODIDE IN MOLTEN NITRATE EUTECTICS

Besides the known oxidation of iodide in molten nitrates to form iodine (e.g. at greater-than-or-equal-to 220-degrees-C in LiNO3-KNO3 eutectic), a further oxidation has been observed at higher temperatures (greater-than-or-equal-to 400-degrees-C) to form I(VII) as paraperiodate. This anion has been found to precipitate in pure lithium nitrate-potassium nitrate eutectic, and in sodium, nitrate-potassium nitrate or lithium nitrate-potassium nitrate eutectics when containing calcium nitrate (as Li5IO6, Ca5(IO6)2 and LiCa2IO6, respectively). Although it does not react significantly with iodate in pure nitrate melts, iodide is oxidised readily in the presence of protonic acids (NaHSO4, KHSO4 or sulphamic acid), as are solutions of iodide alone.