a polyhalide light - polarizing material comprising a complex obtained by reacting : elemental iodine ; a hydrohalide acid or an ammonium halide , alkali metal halide or alkaline earth metal halide ; a first compound capable of chelating hydrogen , ammonium or metal ions ; and a second compound comprising at least one chelating group present in the first compound and either at least one group of the first compound is changed to a different group or the second compound comprises at least one additional group .