On Apr 17 2005, 12:19, Teo Zenios wrote: pure get it That temperature is for powder or dust. It's much higher for bulk solid magnesium, normally quoted as 625C or thereabouts, though lower than its melting point (648C). There are various factors that affect ignition temperature. See for example: http://www.netl.doe.gov/coolscience/res_archive/q&a_36.html http://www.eh.doe.gov/techstds/standard/hdbk1081/hbk1081c.html and for common alloys: http://www.parkwayproducts.com/thixomolding/engineering_data.html Oh, and for some more pictures of what happens when it does burn, and how hard it is to make that happen: http://www.theodoregray.com/PeriodicTable/Stories/012.2/ By the way, titanium dust and grit is worse than magnesium dust; when turning titanium you're supposed to use water-based collant to avoud ignition risk -- but it's only a few months ago I had my titanium spectacle frames welded back together. Aluminium too; damp aluminium dust will spontaneously ignite (another standard school chemistry demo, it used to be mixed with iodine to produce purple smoke) and its bulk ignition temperature is lower than that of magnesium's, but I've seen its auto-ignition temperature quoted as high as 780C. I suppose the reason I've replied to so many of the posts about this is that people remember seeing magnesium ribbon burning in school chemistry classes, but Real Life ain't like the science lab. -- Pete Peter Turnbull Network Manager University of York