In the presence of fluoride ion,  $M{n}^{2+}$ can be titrated with $Mn{O_4^{-}}_{ }$ , where both reactants being converted to a complex of Mn(III). A 0.458g of sample containing $M{n}_3{O}_4$  was dissolved and all manganese was converted to $M{n}^{2+}$ . Titration in the presence of fluoride ion consumed 30.0 ml of $KMn{O}_4$  that was 0.125 N against oxalate. (Mn = 55)