Complexometric Titration of Mn II in Solution

Weigh out accurately about 4.50 g purest MnS04.(NH4)2S04.6H203 dissolve in slightly acidified water and make up to 250 cm in a volumetric flask. Pipette 2S.0 cm of the 

2 Complexometric determination of manganesefll) ions in presence of magnesium ions 

Both ions can be titrated with EDTA, the titre gives the sum of their concenu tions. When NaF is then added, it will form Mgp2 from the Mg complexonate. When excess of Mn(II) ion solution is then added, the excess can be back-titrated against EDTA. Prepare a solution approximately 0.05 M in Mn(II) and 0.05 M in Mg. Pipette 25.0 cm of the mixed solution, treat as above and record the average titre of 0.05 M EDTA. At the end point, add 2.5 g NaF and agitate to dissolve for a minute, then introduce from a burette the standardised Mn(II) solution in 1 cm portions until a permanent red colour is obtained and then add a slight excess. After recording the volume used, titrate with standardised EDTA to the blue end point. Calculate from the titres the concentrations of Mg and of Mn(Il) in mol dm . 

Solutions of Mn(Il) salts can be titrated with potassium permanganate in presence of pyrophosophate. If a Pt and a saturated calomel electrode dip into the solution and connected to a potentiometer (Sec.2.5.1) (or pH-millivolt meter), a large change in the potential of the Pt electrode is observed when the Mn(lII) pyrophosphate complex is formed according to  

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