A piece of iron wire of mass 2.225g was put into a conical flask containing dilute sulphuric acid. The flask was fitted with a bung carrying a Bunsen valve, to allow the hydrogen generated to escape but preventing air from entering. The mixture was warmed to speed up the reaction. When all the iron had reacted, the solution was cooled to room temperature and made up to 250cm^3 in a graduated flask. With all these precautions, iron is converted to Fe^2+ ions only and no Fe^3+ ions are formed. 25.0cm3 of the solution were acidified and titrated against a 0.0185 mol/dm^3 solution of potassium dichromate (VI). The volume required was 31.0cm^3. Calculate the percentage of iron in the iron wire.