While skiing as a young teen, I was introduced to the wonders of reusable handwarmers, which use supercooled molten sodium acetate in some sort of exothermic crystallization reaction to keep your extremities from turning that nice shade of blue.

Vehicle catalytic converters do not perform well at all until they reach a certain light-off temperature, which is well into the 400 to 600 F range. It takes a few minutes for the exhaust temperatures at the converter to reach that temperature, and so a sizable portion of vehicle emissions control is a function of getting the converter to temperature as quickly as possible.

I am not a chemist, and am not certain that the temperatures and available heat energy from a sodium acetate reaction or a similar one would be that significant in terms of improving catalytic converter warm-up times, but I'm really quite curious to find out.
-- RayfordSteele, Apr 09 2010

random, halfbakery