Q.Find percentage of oxygen, silicon, aluminium and iron in earth's crust.

Wrought iron is the purest commercially available form of iron.

Iron is produced and used in several forms, differing mainly in carbon content and impurities:

• Pig iron — the crude form obtained directly from the blast furnace; contains the highest impurity level (~3–4.5% carbon, plus Si, Mn, P, S). Brittle and least pure.
• Cast iron — made by remelting pig iron with scrap iron and coke; still has high carbon content (~2–4%). Hard and brittle, used for casting.
• Steel — an alloy of iron with a controlled, much lower carbon content (0.1–1.5%) plus other elements; strong and useful, but still an alloy, not pure iron. …