Titrimetric Estimation of Hexacyanoferrate(III) With Iron(II) in Presence of Pyrophoasphate and Acetic Acid Medium

These methods are not entirely satisfactory and suffer from one disadvantage or the other. For example, most of the reductants are not susceptable to aerial oxidation and hence required special apparatus for their storage under inert atmosphere. Potassium hexacyanoferrate(III) is well known as a oxidant particularly in alkaline medium and useful oxidemetric titrant known from a long time Berka&zyka1 determination of numerous inorganic and organic substances. Some other reductents employed are expensive and the procedures reported are tedious and time consuming. The method developed using iron(II) in presence of fluoride affects glass-ware. Murthy and et.al; determination of HCF(III) iron(II) in phosphoric acid medium2 for the first time not succeed in developing a visual end-point method using a redox indicator, because of the reported formation of a deep blue colour during the titration. We have now developed a direct visual end-point method for the determination of HCF(III) with iron(II) in presence of pyrophosphate and acetic acid medium employing thiazine dyes used as redox indicators keeping zinc sulphate in the rection medium to prevent the formation of blue colour during the titration. The method now developed does not suffer from any of the disadvantages associated with the earlier methods

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