[constant thinker]

I was kinda wondering exactly what is in those hand warmers. The ones you use when you go snowboarding or skiing.

I'm guessing that one of the things in it is Fe because when I opened one it looked just like rust. Oxidizing iron wouldn't give off that much heat. Would it?

I just wanna wanna know what is in those things outta curiosity.

[Mitch]

Have you checked the manufacturer's website?

[jdurg]

From what I remember back in high school chemistry class, I think those packets contain a supersaturated solution of sodium thiosulfate.  When you click that little disc inside of it, it catalyzes the precipitation of the thiosulfate which release a LOT of heat.  Still, Mitch's suggestion of going to the manufacturer's site is the best idea.

[movies]

From what I remember back in high school chemistry class, I think those packets contain a supersaturated solution of sodium thiosulfate.  When you click that little disc inside of it, it catalyzes the precipitation of the thiosulfate which release a LOT of heat.  Still, Mitch's suggestion of going to the manufacturer's site is the best idea.

There are many different types with many different things in them, I'd bet.  I used to use the ones that jdurg mentioned.  They are nice because you can reuse them by putting the packets in boiling water for a while.

The other type probably have some sort of oxygen activated reaction because they start to heat up as soon as you take them out of the plastic bag.  They aren't reusable though, probably because it would be tough to reduce whatever it is that got oxidized by the oxygen....

[constant thinker]

Yea the ones I've used say warning do not put in an oxygen rich enviroment. That probably means it creates heat by oxidizing something. I figured some of them must contain salts but I'll take mitch's advice and check their website.

[mithrilhack]

MRE packets use a iron-magnesium substance and water.