posted by emily .
Fe3+ is added to excess Ag+ prior to titration with KSCN. When all the excess Ag+ has reacted, the red complex of Fe(SCN)2+ forms. This red complex is visible when the [SCN-] is about 2x10^-4M. at this pt. >99% (but not all) of the Ag+ has precipitated. Calc. the Ag+ when the Fe(SCN)2+ forms.