>
> When we raced the VW engines in the formula Vee class SCCA we had a fire
> bottle in the car with a chemical called purple K designed for magnesium
> fires
>

Yeah, Purple K (potassium chloride) is one of the few things that can put
out burning magnesium. Really, the only way to put out burning metal is to
apply something to it that's dense and massive enough to absorb the heat of
the reaction and cool it down to the point where it's no longer self
perpetuating. Burning magnesium is nasty stuff. Water is bad because it just
gives it more oxygen and adds a cloud of burning hydrogen on top of it. CO2
does nothing but add oxygen and leave behind carbon and carbon monoxide gas.
And never, ever, EVER try to put out a magnesium fire with a Halon fire
extinguisher. That produces phosgene gas, which was used in WW1 as a
chemical weapon. Nasty, nasty stuff. The recommended way to put out burning
magnesium is to carefully cover it with sodium chloride or DRY sand to act
as a thermal ballast to sink the heat out of the reacting metal.
--
John Bange
'90 Vanagon - "Geldsauger"