On Wed, 10 Jan 2007 20:30:36 -0800 Jim Cathey <[EMAIL PROTECTED]> wrote:
> > The hydrogen certainly helped start the conflagration, but it was the > > nitro- based paints that really caused the problems. > > Saw a special on that. The hydrogen didn't start the fire, it was > a spark across improperly grounded skin panels. The fabric doping, > new for the Hindenburg, was a mixture of aluminum powder and iron > oxide. Yes, thanks for correcting me on that. > Anybody else remember the formula for thermite? http://en.wikipedia.org/wiki/Thermite A thermite reaction is a type of aluminothermic reaction in which aluminium metal is oxidized by the oxide of another metal, most commonly iron oxide. The name thermite is also used to refer to a mixture of two such chemicals. The products are aluminium oxide, free elemental iron, and a large amount of heat. The reactants are commonly powdered and mixed with a binder to keep the material solid and prevent separation. The reaction is used for thermite welding, often used to join rails. Black or blue iron oxide (Fe3O4), produced by oxidizing iron in an oxygen-rich environment under high heat, is the most commonly used thermite oxidizing agent because it is inexpensive and easily produced. Red iron(III) oxide (Fe2O3, commonly known as rust) can also be used to make thermite and yields a significantly more energetic reaction. Other oxides are occasionally used, such as in manganese thermite and chromium thermite, but only for highly specialized purposes. Both examples use aluminium as the reactive metal. In principle, any reactive metal could be used instead of aluminum. This is rarely done, however, because the properties of aluminium are ideal for this reaction. It is by far the cheapest of the highly reactive metals; it also forms a passivation layer making it safer to handle than many other reactive metals. The melting and boiling points of aluminum also make it ideal for thermite reactions. Its relatively low melting point (660°C, 1221°F) means that it is easy to melt the metal, so that the reaction can occur mainly in the liquid phase[1] and thus proceeds fairly quickly. At the same time, its high boiling point (2519°C, 4566°F) enables the reaction to reach very high temperatures, since several processes tend to limit the maximum temperature to just below the boiling point.[2] Such a high boiling point is common among transition metals (e.g. iron and copper boil at 2887 °C and 2582 °C respectively), but is especially unusual among the highly reactive metals (cf. magnesium and sodium which boil at 1090 °C and 883 °C respectively). Although the reactants are stable at room temperature, they burn with an extremely intense exothermic reaction when they are heated to ignition temperature. The products emerge as liquids due to the high temperatures reached (up to 2500 °C (4500 °F) with iron(III) oxide)___although the actual temperature reached depends on how quickly heat can escape to the surrounding environment. Thermite contains its own supply of oxygen and does not require any external source of air. Consequently, it cannot be smothered and may ignite in any environment, given sufficient initial heat. It will burn well while wet and cannot be extinguished with water. Small amounts of water will boil before reaching the reaction. If thermite is ignited underwater, the molten iron produced will extract oxygen from water and generate hydrogen gas in a single-replacement reaction. This gas may, in turn, burn by combining with oxygen in the air. It continues, talking about how to ignite it "safely." Craig
