Highest Oxidation State of Iron Ferrates VI

Like other 3d transition metals, the highest oxidation state is more stable in alkaline media. However, these oxidation states become less stable beyond Mn. The highest state available for iron is +6, attainable in alkaline solution when iron(lll) species are oxidised by a strong oxidant. The tetrahedral ferrate(VI) is like the tetrahedral MO4] ions of the earlier 3d metals. 

Prepare 0.5 M iron(lll) nitrate solution acidified to prevent hydrolysis. Prepare 2 M solution of NaOCl in water. Dissolve 2 g NaOH in 50 cm of the solution. Heat to boiling and add, dropwise, the iron solution until there is no change in colour. Boil the mixture for 2 minutes. Filter the suspension through a glass wool plug and collect the filtrate in a conical flask. Add slowly to the filtrate barium chloride solution while stirring. Filter the precipitate under suction, wash with a little water and dry by pressing between filter paper under suction. 

Add dil. HCI to part of the solid, quickly insert a glass wool plug in the test tube and test with a glowing splint. When completely dissolved, add to separate portions 

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