How to Determine the Temperature at Which Carbon Can Reduce Iron Oxide to Iron

Smelting is a process by which iron (iii) oxide is reduced to elemental iron.

Iron occurs naturally as iron ore, which is a compound of iron and oxygen, commonly as iron (iii) oxide. In order to separate metallic iron from this ore, the material must go through a smelting process. This process uses carbon to reduce the iron in the compound to its elemental form. Smelting takes place in large blast furnaces at temperatures above 1832 degrees Farhenheit and the reduction takes place at a temperature below the melting point of iron, which is 2795 degrees Farhenheit. It is possible to experimentally determine the temperature at which this reduction can occur.

Things You'll Need

• Iron (iii) oxide
• Carbon (wood charcoal)
• Hard-glass test tube
• Tongs
• Bunsen burner
• Heat mat
• Test tube holder
• Magnet
• High-temperature (1500 degrees Celsius/2732 degrees Farhenheit) thermometer
• Safety goggles
• Thermal safety gloves
• Protective lab apron

Instructions

1. Light the Bunsen burner.

2. Mix iron (iii) oxide powder with the carbon powder in a test tube.

3. Run a magnet under the glass of the test tube to see if there is any magnetic reaction or movement in the powder mixture.

4. Hold the test tube in a pair of tongs and heat its bottom in the hottest part of the Bunsen burner flame. Do so for five minutes.

5. Remove the test tube from the flame. Use the thermometer to take the temperature of the mixture in the test tube. Record this data.

6. Set the test tube in the test tube rack on the heat mat, and allow it to cool to room temperature.

7. Run a magnet under the glass of the test tube to see if there is any magnetic reaction or movement in the powder mixture. If there are no signs of magnetism, repeat steps 4 through 7, heating the mixture a minute longer each time, until you do.

8. Record the temperature at which magnetic properties are first noticed.

Tips & Warnings

• Because it is bonded to oxygen, iron (iii) oxide does not have magnetic properties. When in its elemental form, pure iron does have magnetic properties.

• The reduction of iron (iii) oxide to elemental iron occurs between 1652 and 2552 degrees Farhenheit in a blast furnace. This is approximately the temperature at which you should see magnetic properties start to occur.

• This experiment requires heating materials to an extremely high temperature. Follow proper lab safety techniques to avoid injury or death.

• Do not use equipment in this experiment that has not been rated for temperatures up to 2732 degrees Farhenheit. This is particularly important for the thermometer and the test tube.

References

• Practical Chemistry: Where Does Carbon Come in the Reactivity Series?
• ChemGuide: Iron and Steel
• Chemical Elements: Iron (Fe)
• Web Elements: Iron
• WLU: The Basics of Bloomery Smelting
• Smart 2000: Reduction and Ceramics Firing

Resources

• University of Bradford: Experimental Iron Smelting at Rievaulx Abbey