Chemical experiment not going well

With my 7 year old, I was trying to do a simple experiment, which is
extraction of oxygen and hydrogen from water by means of electrolysis.
To that end, we used magnesium sulfate (epsom salt) as electrolyte,
insulated copper wire with bare ends for electrodes, and a DC power
supply for electricity.
We collected hydrogen and oxygen into separate test tubes.
The part that did not work is that only one of the electrodes produced
any gas at all, and there was no gas coming out of the second
electrode. After a while of this, one test tube filled with gas and
the experiment stopped as the water was displaced from that
electrode.
So, my question is how come there is no gas on the second electrode.
I do not understand why this is so, given that both the experiment
book as well as Wikipedia says that magnesium should not oxidize?
The water acquired bluish tint.
WTF?
Reply to
Ignoramus25884
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electrolysis.
produced
You're getting copper sulfate, magnesium (hydr)oxide, and hydrogen.
Change to a mild acid. Use stainless steel electrodes.
Try a 5% solution of sulfuric acid (battery acid).
LLoyd
Reply to
Lloyd E. Sponenburgh
plain salt water is the easiest and safest.
Reply to
Cydrome Leader
Bluish tint sounds like the copper is oxidizing (though using up *all* the oxygen seems a bit much). Googling around, I've seen a suggestion of using pencil lead as the electrode.
Reply to
Joe Pfeiffer
Carbon electrodes will also work, and you won't have them oxidize. Take a pencil with a thick lead and cut the wood off of it. Magnesium sulphate will work fine.
Reply to
Madalch
if not for the stink of chlorine
Reply to
Ignoramus25884
Your voltage is too high if you are making chlorine.
here's some useful info
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Reply to
Cydrome Leader
carbon electrode for arc lamps work great, assuming you can find any. Even with them, the anode starts to powder and fall apart.
Pretty much any electrolytic cell is going to turn nasty looking/into sludge.
Reply to
Cydrome Leader
I have some EDM carbon pieces, they should work I think.
Reply to
Ignoramus25884
if they're made to conduct electricity, they should be ok. pencil lead is clay and other junk, it's not that good of a conductor.
Reply to
Cydrome Leader
"Cydrome Leader" wrote: (clip) carbon electrode for arc lamps work great, assuming you can find any. (clip) ^^^^^^^^^^^^^^^^^^^ If you do find carbon arc electrodes, they will be copper clad. An easy source for carbon rods is flashlight batteries (cells, actually.)
Reply to
Leo Lichtman
Not in the alkaline style. It's positive electrode is a ribbon.
You can still get carbon zinc cells (with the carbon rod):
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--Winston
Reply to
Winston
I can't believe kids nowadays have to grow up without those gigantic 1.5v cells with the little screw terminals on top. They were a little biggera round than, and a bit taller than, a container of frozen orange juice, lemme go look...
Oh yeah, the No.6 dry cell/ignition cell/ telephone system cell!
Bigass carbon rod in one of those.
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Dave
Reply to
spamTHISbrp
I remember as a kid playing with automatic pencil leads and AA NiCads, that the leads conducted well enough to glow white hot and burn away if they didn't pop first.
Reply to
David Billington
Do they still sell those things? I thought RoHS meant the death-knell of the dry cell (because of its mercury content).
Reply to
Mark Thorson
Cydrome Leader fired this volley in news:ghk384$rui$ snipped-for-privacy@reader1.panix.com:
If you want chlorine gas as part of the product...
LLoyd
Reply to
Lloyd E. Sponenburgh
The reason you're not seeing any hydrogen is that the electrons at the cathode that would release it are producing magnesium instead which reacts with water if finely divided and it is turning into magnesium hydroxide. Years ago when I built a welder using an aircraft generator I made a electrolytic cell consisting of a glass bottle with salt water in it and two carbon electrodes protruding through the cork. With this device I could determine the polarity of the welding circuit by the greater amount of bubbles released at the negative terminal. Engineman
Reply to
erngineman
This probably isn't going to work well for you if you don't use platinum as an electrode. You were getting hydrogen off of the cathode, but the anode was reacting with the oxygen as soon as it was produced, so you never saw it. (Obviously, you'd only gotten half as much as the hydrogen, anyway.)
Maybe these guys can help.....
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Reply to
Gene
12 volt "lantern" batteries were an whopping $30 something last time saw one at a radio shack a few weeks ago. they must have been like $5 when I used to play with them.
I was surprised to see them at all in fact.
Reply to
Cydrome Leader
You don't get weird secondary reactions if you stick with the lowest possible voltage.
Use the largest flattest electrodes you can, as close as possible. The lower the resistance of the cell, the more current flow you get- which means you get more gas.
you can also use baking soda, it's cheap and won't corrode everything near you.
I've made gas generators in 500Ml nalgene squirt bottles. If you run enough current though it you ge the water to boil and end up with more steam than gas, which is a problem if you want hydrogen and oxygen for a fire.
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has a section about how their electroyltic cells work. The torches they make are pretty nifty as well. The amount of heat they produce for the size of the flame is incredible, especially for soldering.
Reply to
Cydrome Leader

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