I live in Japan. I would like to evolve hydrogen to demonstrate to my son buoyant balloons (we have helium aerosol cans here which barely fill one balloon). There are drain cleaners here with low concentration of sodium such as up to 4% and say safe for aluminum (probably the calcium hydroxide also contained). I have obtained some wire and batteries and I think electrolysis could help- what should I do for the best chance of evolving hydrogen?

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    $\begingroup$ It depends on the nature of the sodium compound. If it is sodium carbonate, the reaction with aluminium is extremely slow. If it is sodium hydroxyde, a 4% solution will quickly react with aluminium and produce a lot of $\ce{H2}$ bubbles. But take care! The bubbles have a tendency to sweep and fill the flask. Take also care and of the droplets emitted when the bubbles blow up. They contain $\ce{NaOH}$ which is corrosive. $\endgroup$
    – Maurice
    Apr 24, 2021 at 8:13
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    $\begingroup$ Getting a little hydrogen at home is easy. Getting enough hydrogen at sufficient pressure to inflate a balloon is another story, though. $\endgroup$ Apr 24, 2021 at 9:04
  • $\begingroup$ @Ivan: Mylar balloons can be purchased without helium inside and can be inflated easily to the point where they will float in air. But they will still look floppy. $\endgroup$ Apr 25, 2021 at 13:55

1 Answer 1


First, any drain cleaner that is at all effective is probably not safe for a child to use, even under adult supervision.

Second, you can easily produce enough hydrogen to inflate a plastic bag, perhaps one to four liters, using electrolysis. Unlike an elastic balloon, the bag will not resist inflation appreciably until full. Try carbon electrodes (e.g., from zinc-carbon cells) with $\ce{MgSO4}$ (Epsom salt) in water as the electrolyte. You can also capture oxygen generated and test it with a glowing wooden splint.

It is an exercise for the experimenter to calculate how many ampere-hours it would take to inflate the specific bag.

BTW, you might want to perform this outdoors, in case a spark sets off the hydrogen!

  • $\begingroup$ How do I use a plastic bag to collect Hydrogen? $\endgroup$ Apr 25, 2021 at 10:36

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