Thread: Hydrogen from magnesium and vinegar

Hi;
I want to fill balloons with hydrogen. I have magnesium turnings (look like stamp-sized corrugated and cracked flakes of metal foil) and vinegar. So far, so good.

Problem is, when I put some of those into a bottle and pour vinegar over them, what I get is a violently bubbling, dirty-looking foam that bursts out of the bottle like boiling milk, magnesium and all. If I put a balloon on top of the bottle, it will get filled with this stuff instead of just hydrogen gas.

How can I make the foam settle? I suppose getting magnesium in a more massive form (such as bars or large pellets) might help, but I wouldn't like to waste too much time and money shopping for various shapes and sizes which might again prove useless.

TIA, L.L.

It sounds like you're having problems with impurity. You need to make sure that the magnesium isn't covered in magnesium oxide and that the vinegar is good quality. You probably are producing hydrogen, albeit along with who knows what else. Have you tried burning the gas? Hydrogen burns with a pop.

The other problem is keeping the foam in check, that's more of a problem with the method you're using, the foam is caused by the gas that is being evolved. Try stoppering the bottle and have a straw coming out from the top that feeds into the balloon. That might reduce the amount of foam spilling.

Thanks for your reply.

I don't care how pure my hydrogen is; I just want the baloon to fly. 80% H2 is fine by me.

Yes, my problem is controlling the foam. The way it behaves, I think it would squirt right through the straw; one advantage though is most of the magnesium would stay behind.

I am also thinking of putting the magnesium in some kind of fine mesh (a piece of stocking?) with a piece of steel or glass to weigh it down, so the thin metal will not float with the bubbles.

As for the quality of the vinegar, I think the worse (from a cooking point of view) the better for my experiment. Good quality cooking vinegars would have some extra tasty organic stuff from fruit (such as grapes if it's made from wine), while the cheapest vinegar is just diluted acetic acid.

If you aren't worried about how you make the hydrogen then just use electrolysis. Get a cup of salty water and place two pieces of conducting metal into it, each of which are connected to opposite terminals of a battery. When you switch on the current hydrogen will be produced at one electrode and oxygen at the other in the ratio 2:1. Just stick a bottle or something above the electrode and you'll get your hydrogen.

Electrolysis would take forever to fill a balloon. Besides, I want to do this experiment outdoor, with kids. No electric mains.

Oh ok, that's fair enough then. The best solution to your foam problem would then be a container that is tall enough to compensate for the height of foam that is produced. It would ideally be tall and narrow, otherwise you won't build enough gas pressure to inflate the balloon. Something like a conical flask maybe?