Permanganate iodometric titration

An alternative method for the analysis of permanganate is the use of conventional iodometric methods (177) where excess potassium iodide is added to a solution of permanganate under acidic conditions. The Hberated iodide is then titrated with standard thiosulfate solution using starch as an indicator. 

Redox (reduction-oxidation) titrimetry is used primarily for nitrate detns. Five systems are in current use ferrous sulfate—dichromate, io dome trie, periodic acid oxidation (NaOH titrant), K permanganate, and titanous chloride-ferric ammonium sulfate. The ferrous sulfate— dichromate system is used for MNT DNT detns (Vol 2, C162-Lff Vol 6, F17-Rff Ref 17). In the iodometric procedure, the sample (ie, NG) is treated in a C02 atm with a satd soln of Mn chloride in coned HC1, the vol reaction products are bubbled thru a K iodide soln, and the liberated iodine is titrated with standard thiosulfate soln (Refs 1 17). The periodic... 

Potassium permanganate oxidises arsenious acid rapidly and quantitatively in the presence of a trace of potassium iodide, which acts catalytically.7 The reaction takes place in the presence of mineral acid and the use of an indicator or of sodium bicarbonate is unnecessary. The titration may be carried out at any temperature up to 95° C. A slight correction is necessary for the oxidation of the iodide other iodides are less effective than the potassium salt. This method is comparable in accuracy with the iodometric method. 

The ferrous-ferric ion analytical technique was used to determine the ozone concentration of the stock solution. Enough ferrous ammonium sulfate was added to an aliquot of ozone to bring 100 ml. of the solution to about 0.005iV and the nonoxidized ferrous ions were then back-titrated with 0.1 A potassium permanganate. The chlorine concentration was determined iodometrically (2). 

In the case of stabilisers which consume permanganate under these conditions, the determination is done iodometrically by adding 1 g KI to the acidified solution and titrated the iodine liberated, after keeping in dark for 10 min, with O.IN sodium thiosulphate using starch as an indicator. 

The isothermal method was used. Ten to twelve hours were allowed for equilibration. The nitrite ion content was determined by the iodometric back titration of excess permanganate. The phosphate ion content was determined gravimetrically as Mg2P20y... 

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