[en] The excess of iodine in mercury(II) iodide crystals was determined by spectrophotometry. Dynamic dissolution of mercury(II) iodide samples in carbon tetrachloride allows the detection of minute amounts (<1 μmol mol^-1) of free iodine in the crystal. This method has a detection limit that is at least two orders of magnitude lower than for other methods for the determination of excess iodine. Many crystals grown under various iodine overpressure conditions were studied. The solubility limit of free iodine in mercury(II) iodine was found to about 130 μmol mol^-1 in the range 95-120degC. (author). 15 refs.; 1 fig.; 1 tab