connecting wires to pencils underwater

Alligator clips (test clips) covered with Sugru (check sparkfun.com ). The teeth of the clips will make good contact with the pencil "lead" and the Sugru (a moldable silicone that dries hard in 24 hours) will provide water proofing.

That's an "artist's impression"

Copper electrodes will work too but will taint the water, with carbon electrodes some carbon decomposes at the anode but the CO2 formed has the same volume as the O2 it replaces so the text books ignore it when discussing stochiometry.

If the goal is to produce more than samples of the gasses, for improved results use stainless steel electrodes for electrolysis in a dilute caustic soda solution.

Run insulated wire all the way up in the test tube, then down to the pencil above the liquid level. Here:

test tube +------------+ | +--+ | | | | | | | P | | | E | | W N | |**I**C *****|

Not shown in the pictures linked in the original post is that the setup starts with the test tubes full of water.

Not a bad idea.

I'm probably going to use plastic tubing leading to some kind of vessels rather than test tubes.

:-)

Good point. I could probably connect the wires to some bits of stainless with small bolts & nuts, then shrink-wrap over them.

Does that make a difference?

Ed

only if the goal of the looping the wire round to the top like that was to keep it dry

That looks like fun stuff, thanks.

What would happen with zinc-plated steel (bolts, for example)?

probably be pretty messy, unplated steel would be better.

The zinc will probably get involved. Remember the copper/lemon juice/zinc battery from grade school science?

-- Les Cargill

Well, I was tinkering around with a scrap bit of stainless steel rod (unthreaded) & trying to figure out how to attach a wire to it so I could shrink-wrap the connection; then came up with the idea of a stainless steel bolt & an eye crimp; then realized I only have (AFAIK) zinc-plated & brass bolts, no stainless ones.

I figured that would probably be the case, but it doesn't hurt to ask (usually).

silver solder if you're equipped, borrow a spot welder for 20 seconds, plate the end with copper and solder to that, even a bullet type connector as used in auto electrics.

Checking my Rolodex to see if I know anyone with a spot welder...

Thanks again for the tips.