Put some in a bottle along with tin foil, add water and pull a balloon over the top. Watch as it inflates and there, you have a balloon o' hydrogen.
It can manipulate your voice in a similar way to helium, but it's cheaper, or when mixed with oxygen and lit it can manipulate other people's voices into sounding as though they're muted, along with sounds of any sort really.
Warning: Caustic soda is very caustic, as one might understand. Getting it in your eyes is actually worse than getting a strong acid there.
Allso, a mixture of hydrogen and oxygen is quite volatile.
You didn't hear this from me.