Comment: Or

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Or

Molten aluminum with impurities picked up from the room it was in? Aluminum can glow yellow with impurities, but I don't know for sure if that's what occurred.

Could also have been from the melted lead and copper batteries on that floor? The floor was a storage floor for UPS units.

http://11-settembre.blogspot.com/2007/02/ups-on-81st-floor-o...

Gives the most likely explanation, in my mind.

It's most likely a combination of aluminum, lead, and copper, given what was on the floor. We know it can't be steel because the temperatures wouldn't have been hot enough.

http://www.sintef.no/home/Press-Room/Research-News/New-theor...

Gives an interesting alternative explanation of what occurred. I hadn't thought of the molten aluminum meeting the sprinkler system, but that'd definitely explain the explosions heard. Not sure if he's right, but it's plausible.

Eric Hoffer