Chemical Reaction
Ration heaters generate heat in an electron-transfer process called an oxidation-reduction reaction. Water oxidizes magnesium metal, according to the following chemical reaction:
- Mg + 2H2O → Mg(OH)2 + H2 + heat
This reaction is analogous to iron being rusted by oxygen, and proceeds at about the same slow rate. On their own, the reaction between magnesium and water is too slow to generate usable heat.
To accelerate the reaction, the developers (see US Patents 4,017,414 and 4,264,362) mixed metallic iron particles and table salt (NaCl) with the magnesium particles.
Iron and magnesium metals, when suspended in an electrolyte (such as salt water), form a galvanic cell -- a "battery" -- that can generate electricity. (For an example of how to build such a battery, see http://www.miniscience.com/link/Airbattery.htm)
When water is added to a ration heater, it dissolves the salt to form a salt-water electrolyte, thereby turning each particle of magnesium and iron into a tiny battery. Because the magnesium and iron particles are in contact, they become thousands of tiny short-circuited batteries, which quickly burn out, producing heat in a process the patent holders call "Supercorroding Galvanic Cells".
Read more about this topic: Flameless Ration Heater
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