A 5.00 mL aqueous suspension of elemental selenium was treated with 25.00 mL of ammoniacal 0.0360 M AgNO3. Reaction:
6Ag(NH3)2+ + 3Se(s) + 3H2O 2Ag2Se(s) + Ag2SeO3(s) + 6NH4+
After this reaction is complete, nitric acid was added to dissolve the Ag2SO3 but not the Ag2Se. The Ag+ from the dissolved Ag2SO3 and the excess reagent required 16.71 mL of 0.01370 M KSCN in a Volhard titration. How many milligrams of Se were contained in each millilitre of sample?