The concentration of free iodine and its variation in the temperature range 10–40°C has been determined by the potentiometric method in nine commercial PVP-iodine products as well as in pure aqueous solutions (1, 5 and 10) of PVP-iodine of the type 17/12 and 90/04. In addition, aqueous solutions of PVP-iodine 30/06 of the same concentrations have been measured in the temperatur range 0–70°C. The commercial products showed a remarkably great spread in the concentration of free iodine (0.2–10 ppm at 25°C), which may be attributed to the different compositions, especially the ratio of total iodine to iodide as well as the kind and quantity of organic-pharmaceutical constituents. All tested PVP-iodine systems showed a significant—and unexpectedly similar—change of the concentration of free iodine by the
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