Redox and redox equilibria

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Why is no indicator used in the titration of ammonium iron(II) sulphate solution against potassium manganate(VII) solution? Also I want to know what made it change to a permanent feint pink colour?
110208

Corrie writes .....
 
From the equation for the reaction taking place in this titration you will know that iron(II) ions and manganate(VII) ions react to produce Mn²⁺ ions and Fe³⁺ ions in solution. Manganate(VII) ions are, as you know, deep purple in solution. All the other species present, as reactants or products, are colourless, or almost colourless, in solution at the concentrations used here. (Mn²⁺ ions are very pale pink, and Fe³⁺ ions are pale yellow-brown).
 
As a result, when you pour purple potassium manganate(VII) solution (from a burette) into ammonium iron(II) sulphate solution (in your titration flask - and almost colourless), the purple colour immediately disappears as the MnO₄^- ions and the Fe²⁺ ions react. This continues until all the Fe²⁺ ions have reacted. Then one more drop of potassium manganate(VII) solution will turn the mixture a permanent pink colour. That's the end-point. No indicator is therefore necessary. Adding excess potassium manganate(VII) solution would turn the mixture purple.

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updated: 12 February 2008