111. Solving a chemistry problem

8. A portion of iodoform CHI3 weighing 0.3501 g, containing indifferent impurities, was dissolved in ethyl alcohol and 40.00 ml of a 0.1082 M solution of silver nitrate and concentrated nitric acid were added. The excess of silver nitrate was titrated with 18.20 ml of KSCN solution with a titer of 0.009699 g/ml. Determine the mass fraction (%) of iodoform in the sample if М(CHI3) = 393.72 g/mol.