There was no explosion, there was no violent scattering of molten particles, and there were no noxious life-destroying gases such as come from the explosion of gunpowder, dynamite, or even the burning of coal. And yet the seething, molten metals in the crucible reached a temperature second or third to the highest ever registered by man. Five thousand four hundred degrees—think of it!—more than half as hot as science tells us is the sun which makes this world of ours habitable.
But what was the result of this temperature which staggers the imagination?
Just this. Doctor Goldschmidt knew that the aluminum had won the prize of battle and had paid the price of victory.
The conquered iron was at the bottom of the crucible, a molten mass of pure metal, while the victorious aluminum, seething on the top, was nothing but slag (aluminum oxide).
Perhaps there may be a little lesson in this drama of the metals, because while the iron was vanquished it emerged from the stress of conflict purified and fitted for its high service to mankind, while the more aggressive aluminum came to the top an almost useless product, ruined by the prize for which it had fought.
Another interesting point about this reaction is that the heat produced by a certain quantity of the mixture is no greater in total volume than the heat that would be produced by the burning of an equal amount of anthracite coal. The difference is that the thermit process concentrates all the heat in a few seconds whereas the coal gives off its heat bit by bit for a long period of time.
The mixture of filings used in this process is called thermit. A technical definition of the product is as follows: "Thermit is a mixture of finely divided aluminum and iron oxide. When ignited in one spot, the combustion so started continues throughout the entire mass without supply of heat or power from outside and produces superheated liquid steel and superheated liquid slag (aluminum oxide)."
Thus the makers of thermit call the pure metal that results from the combustion, thermit steel.
For the boy who has studied chemistry the simple equation by which the scientist described the process to his young friend will mean as much as his long explanation. The equation is:
Fe2O3 + 2Al = Al2O3 + 2Fe.