Complex sentence: In a closed vessel the metal reacts with iodine at temperatures of elevated temperature forming the iodide, at a tunsten filament of 1700 ° C the reverse reaction happens and the iodine and the metall is set free.
Split into simpler sentences: In a closed vessel the metal reacts with iodine at elevated temperature forming the iodide. At a tungsten filament of 1700 ° C the reverse reaction occurs, and the iodine and the metal are set free.