# Trying to displace iron from ferrous sulphate heptahydrate using aluminium foil but nothing has happened

I started by dissolving the sulphate into water and filtering it as I noticed there was a dirty residue lying at the bottom. (I am using ferrous sulphate that is commonly used in gardening.) I then poured this solution into a jar along with torn pieces of tin foil (tin foil being a common name; the foil is made of aluminium). At the start the solution was fairly clear and greenish in colour. A few days later there is no sign of iron collecting at the bottom of the jar and there has been a slight change in colour. The solution is now slightly cloudier and looks more like apple juice. The orange colour makes me think there must be iron oxide being produced. I need to know whether my method for displacing the iron is correct and if elementary iron will be produced.

• No, you can't reduce iron like that, for tin is less active than iron. Tin just sits there and does nothing. Meanwhile, iron is oxidized by air to $\ce{Fe^3+}$. – Ivan Neretin Apr 1 '16 at 11:09
• Take a look at an activity series for more info. – Denton Unger Apr 1 '16 at 11:33
• Isn't tin foil made from aluminium though? – The Garage Chemist Apr 1 '16 at 11:36
• Aluminium, however, is easily passivated in the presence of oxygen. – Jannis Andreska Apr 1 '16 at 19:56

Jannis Andreska is also correct: The passivating oxide on the aluminum is likely preventing the iron ions from reaching the $\ce{Al^0}$ and swiping their electrons.
So, you are correct again: The yellow/orange color you're observing is probably oxidation of the $\ce{Fe^{2+}}$ to $\ce{Fe^{3+}}$, by $\ce{O2}$ in the air.
Regardless, I would recommend adding some table salt $\left(\ce{NaCl}\right)$ to your solution, both to increase its conductivity and also to introduce chloride, which may help to attack the oxide on the aluminum, in tandem with the applied potential.