On Sat, Nov 21, 2009 at 03:25:01AM -0700, Jeshua Lacock wrote: > > On Nov 21, 2009, at 3:03 AM, Erik Christiansen wrote: > > > On Fri, Nov 20, 2009 at 05:10:18PM +0000, Leslie Newell wrote: > >> Carbon dioxide is 66% oxygen (CO2). As aluminum is very active it > >> will > >> strip oxygen out of the CO2. That is also the reason why you should > >> never use a CO2 fire extinguisher on magnesium fires. > > > > However, it is extensively used in fire extinguishers precisely > > because > > it does not give up its oxygen even at hundreds of degrees C. I'm not > > sure of how many thousand degrees magnesium burns at, but it is more > > than 1500, because thermite (magnesium and iron oxide) combustion > > melts > > the iron produced by the reduction of the iron oxide. > > > Correction: "Thermite" is actually a name brand which is a mixture of > aluminum and iron oxide.
You are so right. A bit of magnesium ribbon can be used to start the reaction. Please forgive the typo. > Generically speaking, Thermite is referred to an "aluminothermic" > reaction. It is aluminum's high infinity for oxygen that strips the > oxygen away from the iron oxide. > > I am sure you could also burn (exothermic reaction) magnesium with > iron oxide, however, that would result in such rapid combustion it > would cause an explosion. Your correction of the record is important in that light, and I don't doubt the conclusion. (I've seen photographs of the severely burned arms of a handyman who used a narrow belt sander on rusty iron after his son had used it on aluminium/magnesium alloy. There was an instantaneous incandescent flash, and the skin hung somewhat loosely from his arms.) > I have actually casted iron, steel, nickel, chromium, ferrotitanium, > and even titanium using aluminothermic reactions (you use the oxide > for the metal that you want - like titanium dioxide for titanium). It > is fascinating stuff! I've only seen it used to weld railway line lengths together. I like to stand well back. The other uses are very intriguing. Erik ------------------------------------------------------------------------------ Let Crystal Reports handle the reporting - Free Crystal Reports 2008 30-Day trial. Simplify your report design, integration and deployment - and focus on what you do best, core application coding. Discover what's new with Crystal Reports now. http://p.sf.net/sfu/bobj-july _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
