[Enthalpy]

What happens with hydrogen evolved by the cited flameless ration heater?

The linked http://en.wikipedia.org/wiki/Flameless_ration_heater#Confined_space_hazard suggests it evolves in air, and FAA considers it a "potential hazard" in aeroplanes.

5g silicon for one glass would evolve 1/3 mol hydrogen, enough for a good bang. Can it react with an other compound to disappear? MnO₂ has this function in batteries, but I'm not enthusiastic about it in a teacup.

Better ideas? Or just recommend to use in open space only, which excludes camping tents?

[curiouscat]

How many million packets have been used so far? I don't see any reports of much damage done.

[Enthalpy]

Yes.

Meanwhile I've re-checked the use of MnO₂ in batteries, and it needs also NH₄Cl plus some graphite powder to keep the slurry conductive, and at the end the Zn electrode is only a small fraction of the battery's volume.

Which explains why heating compositions just let the hydrogen evolve.

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Any ideas to degrade silicon's resistance to corrosion? It has probably the most benign oxide and I like it for that, but I understand silicon isn't very common in general chemistry.

Two decades ago people managed to make nanoporous silicon which could be oxidized into nanoporous silica, but this was semiconductor technology, not necessarily affordable as a fuel.

Or an other metal whose oxides and hydroxides are harmless in a tea bag?

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Alternately to the tea bag in drinking water, we might perhaps plunge a tube in the water, hot only at the tip, and long enough to keep the reactants and products away from the cup. Say, magnesium powder in a tube of thin electrolytic nickel that makes the anode instead of iron. Or keep some iron in the nickel tube.

[Enthalpy]

And from organic chemistry, could some insoluble solid react with water? Say, the addition of water on a double bond produces heat. Could that happen at a suitable speed around room temperature? A conjugated diene, for increased reactivity? A triple bond?

[curiouscat]

Just noticed the title and was reminded that I recently used a Lenovo Tablet and that itself would make an excellent water heater. 

[billnotgatez]

@curiouscat
Very Punny

[Enthalpy]

If heating strongly enough, that could be a smoking pun.

[Enthalpy]

So, don't we find anything better than the usual hand warmer or ration heater, separated from the drinking water but transferring heat to it?

I've just re-checked the heat of hydration/absorption/adsorption of silica gel and zeolite: the best ones one need 100g to warm 300g water by 40K, too bad to my taste.

Metals (silicon) that form non-toxic oxides and hydroxides in water? Water addition on multiple bonds or antiaromatic rings?

Or is the brainstorm in a teapot already finished?