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Lesson: Chapter 16 — Changes of Matter

16.4. Extracting metals 7 of 7

Iron in old Sri Lanka

The blast furnace is a modern design, but extracting iron is nothing new — and Sri Lanka has a long history of it.

For extra knowledge

There is evidence that a high level of knowledge about iron extraction existed in ancient Sri Lanka. Archaeological excavations carried out recently in the Samanalawewa area have uncovered a furnace for smelting iron ore which was found to have been operated with the help of the monsoon winds. A team of archaeologists succeeded in rebuilding such a furnace and using it to smelt ore and produce iron. Archaeological records state that the steel needed to make the ceremonial sword of the Arabian emperor was obtained from the land of "Serendib".

The monsoon supplied the blast

We saw that in a modern blast furnace, air heated to 650 °C is blown in from below. In the Samanalawewa furnace that work was done by the monsoon wind — the blast came free.

Assignment 16.2

  1. Collect information about the iron industry of ancient Sri Lanka.
  2. Iron is used to make alloys. Prepare a table of the alloys containing iron, the new properties those alloys gain, and the uses those properties have in manufactured articles.
  3. Discuss with your teacher whether there is any advantage in having slag inside a blast furnace.

A hint for the third question

Remember that the slag floats as a layer on the molten iron — and that keeps the iron from reacting with the oxygen of the air again.