[dongfang]

Hi,
Some friends and I are trying to fly a balloon across an ocean. The balloons carry more or less well sealed container with electronic equipment, but unfortunately fail quite often and splash down in the sea.
Now I want to improve the survivability chances in the sea, or at least get some more data from the long drift. I want to introduce a slight overpressure in the container, to avoid small pressure changes forcing water into it through any tiny leak there might be.
Does someone have a good idea for a chemical reaction that can very slowly produce an inert gas? Well any gas that is not known to harm electronics, like CO_2.
Temperature is around zero C at this time. The reactants must survive a flight up to -50 C and back to 0C. Liquids should be non corrosive and ideally be possible to jelly-fy somehow. The reaction should go on for months, producing a small amount of gas all the time.
Thanks for any suggestions.
Regards
Soren

[Borek]

Makes me think of ammonium nitrite. It slowly decomposes producing water and gaseous nitrogen. Water is not something you want in the container, but it can be absorbed by some drying agent (which you probably should put into the container anyway).

But I am not sure how fast the decomposition is. Plus, if there is a risk the container can be heated (Sun on the beach?), nitrite can explode. Not that there will be much of it, still, it can be dangerous.

All in all I am not convinced that's the best idea, but I feel like it at least points in an interesting direction.