Chemistry: smelting, part 0

Tutoring chemistry, ancient processes are interesting. The tutor begins about smelting.

Smelting is the process of turning ore into pure metal. In simple terms, ore is how it’s found naturally; the pure metal is what’s useful. Gold is exceptional in that it’s often found in more or less pure form. Moreover, a gold nugget can be worth more than its mass in gold. Industrial metals typically aren’t like that: they need to be pure to be useful.

From a simple point of view, the ore is often the oxide of the metal – imagine it’s (Metal)O_n. At a very high temperature, the oxygen will be willing to leave the metal for carbon to become CO₂. That’s why raw carbon, in charcoal or coke form, is needed. To make it more reactive, it can be finely divided. The metal ore is finely divided for the same reason.

Now the crushed up metal ore and charcoal are cast into an oven and heated from outside. For best results, inside the oven there shouldn’t be oxygen supplied so that it is all extracted from the ore. At a high enough temperature, the oxygen will reject the metal for the carbon, leaving the metal pure. That’s very basic smelting.

Nowadays, smelting can be done much cleaner, with electricity. However, until very recently it was done as explained above, and probably still is in many cases.

Source:

thecrucible.org