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This Reaction Makes an Explosive Chemical Snake

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We've all seen test-tube reactions that overflow in long snakes, but this one is so quick it's like someone used a jump-cut on a film. The resulting foam has been studied by NASA for its fire-resistant properties. Too bad it takes sulfuric acid to make the stuff.

Welcome to io9's Word of the Day. Today's word is "aphrogen." An aphrogen is something, generally a liquid, that spontaneously forms a foam when it's heated. (I've tried to find out if butter is an aphrogen, as it foams in the pan if you heat it enough, but so far I've had no luck. Scientist cooks? Let me know.) P-nitroaniline is certainly an aphrogen. We see it at work, when combined with sulfuric acid.

We've seen sulfuric acid at work with sugar. It initiates a process of dehydration, setting the water molecules free while generating a lot of heat. The heat essentially boils the water, and the water turns to steam, escaping the solidifying carbon. The escaping steam creates bubbles the carbon structure, causing it to rise up from a container in a black column. It's impressive to watch, but sulfuric acid and the p-nitroaniline is something else.


Nothing happens until the whole thing heats up to about 230°C. The mixture sits in its little container like the world's most deadly cup of coffee. When it gets to the right temperature, the structure explodes up from the glass. The tower of foam forms in the blink of an eye. The foam is so surprisingly fire-resistant that it has been studied by NASA. The most the foam does when exposed to a flame is glow and slowly melt away. It's an insulator and a fire-blocker.


Shame the best way to make it is with acid, heat, and explosive change.

[Via Science Line.]