Aluminium is prepared industrially by Hall- Heroult process. Various steps in the concentration of ore are given below. Write them in the correct order.
i)The precipitate formed is separated, washed and strongly heated to get alumina.
ii) Crushed bauxite is leached with hot sodium hydroxide solution.
iii) Impurities are removed from the sodium aluminate solution by filtration.
iv) Solution is diluted after adding a little aluminium hydroxide, to precipitate aluminium hydroxide .