Introduction: Electrolysis

Picture of Electrolysis

Electrolysis is the decomposition of hydrogen and oxygen in water. In other words you break apart the molecules that make up water to restore the elements to their original state. In this case both hydrogen and oxygen exist in a gaseous state. In order to perform electrolysis you must run an electric current through water that contains an electrolyte. The electrolyte allows current to pass through the water because pure water, or even tap water for that matter, is not conductive enough to allow electricity to pass through it. The electrolyte I added in this experiment was salt, a common household item.

Step 1: Getting the Stuff

Picture of Getting the Stuff

The materials you will need for this experiment are:

baking soda (it used to be salt but then I was informed that I may have been producing chlorine gas)

Hot water (enough to fill your container of choice)

a container preferably air-tight and definitely clear

a pair of screws (these will act as the electrodes you pass the
current through)

a battery (a nine volt will do nicely for your first try)

Space to work (I barely had any and that made it a lot tougher)

Materials you may want to have, but are not necessary:

a glue gun (to patch up any holes left by the electrodes)

a DC power source so you don't have to worry about the batteries
running out.

a container that can dispense the hydrogen and oxygen (see introduction)

Step 2: Build the Cell

Picture of Build the Cell

Once you've gathered all of the materials you will want to start by drilling two holes at the bottom of your container. (I drilled them at the top) You'll want these holes to be just slightly smaller than the screws you'll be putting through them. You will want the two screws to be as close as possible to each other so as to get the maximum effect when electrolyzing the water. Once you have paced the screws in you may want to hot glue around them so as to create a seal.

Step 3: Baking Soda-water Mixture

Picture of Baking Soda-water Mixture

Tos start this you will want to heat up enough water to fill your container the heat helps saturate the baking soda within the water. Once you have heated the water you will then need to pour baking soda into the water while stirring (don't be shy about this you can saturate a lot of baking soda in hot water.) Dont' let any baking soda gather on the bottom of the container it will effect conductivity.

Step 4: Setting Up the Cell

Picture of Setting Up the Cell

Once you have placed the screws in and mixed in the salt you'll want to get to the main event. Pour the water into the container and place the cap on. Then place the battery, or batteries if your ambitious on the two electrodes. This will create a stream of bubbles that emanate from the probe connected to the negative end of the battery.

Step 5: The Science of Electrolysis

Picture of The Science of Electrolysis

What you will have just witnessed is the separation of hydrogen and oxygen. The negative probe will always produce hydrogen whereas the positive will always produce oxygen. The reason you see very few bubbles coming from the positive end is the result of there being less oxygen in water than there is hydrogen thus resulting in more bubbles of hydrogen than oxygen.

Step 6: Trouble Shooting

You may have encountered some of these probelms during the operation of the cell. The stream may have stopped flowing from the negative and positive end, this may be the result of an insuffiecient connection between the two probes so adjust the position of the battery and the flow will restart. The bubbles may have never been created and that would be the couse of either a dead battery which if your brave enough (unlike some people I know -*Cough*Gerid*cough*-) you can test on your tongue. This may also be the result of non-conductive probes. To fix the latter you will have to find new METAL screws.


bobdabiulder (author)2016-04-26

When I did this with aluminum foil, it would not work if both electrodes were the same metal. One had to copper or something else.

LabRatMatt (author)bobdabiulder2017-03-03

Aluminum is not the best metal for this particular project. You're much better off using stainless steel if you can find some.

russjd (author)2016-12-05

pair of screws (these will act as the electrodes)

is there a better material to use than steel screws?

(Screws are generally made from low to medium carbon steel wire, but other
tough and inexpensive metals may be substituted, such as stainless steel,
brass, nickel alloys, or aluminum alloy. Steel may be coated or plated with zinc, cadmium, nickel, or
chromium for extra protection).

LabRatMatt (author)russjd2017-03-03

Steel plates are probably your best option. Anything else will oxidize (rust) immediately

darkath (author)2016-04-20

wait....... i though hydrogen is off the positive lead..... I am so confused right now.

Lewissunn (author)darkath2016-10-23

Okay, 6 months late but i'll explain anyway.


Hydrogen in water has a charge of +1

Oxygen has a charge of -2

The negative lead attracts the hydrogen because it is the oppisite charge

HenryFlack (author)2016-10-13

Interesting ....

LandonSalvador (author)2016-09-27

Wow great experiment....

trickery89. (author)2016-04-01

Nice, I'm going to try this soon!

PetieE (author)2015-07-18

I'm not sure if this entirely applies to this electrolytic cell, but I am recovering a steel plate with electrolysis for an EEI, and I need to know if using baking soda and water as the electrolyte will produce harmful gases or anything of the sort. I have to choose between NaOH or the baking soda and water. I need the half reaction to support my decision (I suck at doing half reactions and I don't always understand how to do them). If someone could help, it would be much appreciated

BBoyBravo (author)2009-02-03

how do you stop the electrodes and water from getting guey! I' tried more soda, less soda, distilled water, well water, bottled water it always seems to fry the electrodes and it still gets all guey

dknutson (author)BBoyBravo2009-03-09

Simple: use stainless steel plates, and KHO flakes as your electrolyte. Salt produces chlorene gas, bakeing soda produces carbon monoxide!

tyu123456789 (author)dknutson2013-09-01

If you put baking soda in it, it will only make carbon dioxide not carbon monoxide because carbon monoxide is made when carbon dioxide is heated or if theirs not enough oxygen to combine with the carbon atom.

El Mano (author)dknutson2009-03-10

I tried steel rods in baking soda and they rusted; I can't find a good material to make into electrodes. Also, what are KHO flakes?

dknutson (author)El Mano2009-03-12

KHO: Potassium Hydroxide. BTW, Steel will rust, STAINLESS steal should resist corrosion much better.

CameronC (author)dknutson2009-05-06

But its also quite expensive. If this is just for blowing stuff up pointlessly then salt/baking soda and carbon or galvanised electrodes work fine.

El Mano (author)CameronC2009-05-06

Where can I find some good carbon electrodes that won't corrode?

find d batteries that say super heavy duty, or open a lantern battery that says it is a magnesium carbon battery or a zinc carbon battery.

Forgive me for being cautious, but I prefer to know what I'm dealing with. I got ahold of 4 Panasonic Super Heavy Duty C cells. I tore the jacket off of one of them, and there's a metal canister inside. Now I'm going to be cynical and assume that the can is filled with some sort of chemical with an unknown level of toxitity. Can I just take a hacksaw to said canister, or will it explode, combust, and/or leak poisons all over my hands? (And once disassembled, what's a use for the contents?)

brandon8775 (author)El Mano2009-09-20

If you were to cut the battery it would not explode, the acid would leak out and burn a hole in the ground. The only way it would explode was if you cut it open, and then placed it in water. If you did this everyone within a 10 foot radius would be dead. This I have tried this and I have a hole in my dogs house now.

Wait until after this weekend or next, i will have an instructable up with all the precautions necessary for this, plus a better electrolysis method, trust me. just dont open it yet. coincidentally, i have the same batteries to take apart.

I have to laugh. So many ironic things have happened today. I took apart the batteries this afternoon. I you have a better idea for an electrolysis unit, though, I may just wait around to see it before I build the model I have in mind.

just wait a week or less, itll be up, maybe by tomorrow or monday

the best materials are carbon rods. they cant short out the ciruit and they wont oxidise.

14860 (author)dknutson2009-05-12

Sodium bicarbonate + H2O = Carbon Dioxide I think (which is harmless) and sodium hydroxide. Is that correct?

wolfmain (author)2013-08-27


wolfmain (author)2013-08-27

Baking soda works perfectly fine, I would know, the carbonate poly atomic anion won't break up, but if you're really picky, use sulfuric acid. Your electrolyte must be made of a group 1 or 2a group metal cation (check periodic table) and A poly atomic anion, such as SO4 or CO3. If it's a halogen, you'll get the halogen gas instead of oxygen, and a hydroxide in your water. Halogens can kill you. Use graphite for you positive electrode and copper wire for your negative.

werd608 (author)2013-03-12

Do I cut completely through to the other side

ubuntuPenguin (author)2011-05-18

is vinegar a good electrolyte to use? does it produce any dangerous gases?

S3anyBoy (author)2008-04-07

I have a charger from my old laptop that outputs DC, but I don't know what would be negative and what'd be positive.

beavercleaver (author)S3anyBoy2008-07-24

One output wire will have a white stripe or dashes on it, that is your positive. You seriously need a DVOM, they are really cheap, and necessary for any electrical experiments.

Actually, a white striped wire usually indicates a negative, and dashed indicates positive. It took me a long time to figure that out when I couldn't figure out why all my projects wouldn't work.

Not in the automotive electronics world, dashes do not exist on wires. A DVOM is the only way to be sure what you are working with.

Tombini (author)S3anyBoy2008-10-03

a simple solution (get it) is to set up the apparatus and check which one bubbles ~20 times more. This is the hydrogen

professorred (author)Tombini2008-11-14

fyi, there is 2 times as much hydrogen as there is oxygen. not 20.

Tombini (author)professorred2008-11-15

Urrrghh, I meant by volume! Hydrogen is roughly 10 times less dense than oxygen, so if there is twice as much hydrogen you get 20 times in volume. I have done this test many times the hydrogen filled up a test tube and the oxygen was barely 1cm full

Default117 (author)Tombini2009-03-12

To correct you on your math: if you were going by densities, then there would be two Hydrogen atoms and One Oxygen atom (if you were to split a single water molocule). The two Hydrogen atoms would equal one fifth of the Oxygen atom.

Tombini (author)Default1172009-03-14

Lol, smartypants... still the basic rule applies, whichever bubbles more is the Hydrogen

marmique123 (author)Tombini2010-02-09

aww... my friends said that its just boiling water... not hydrogen gas >o<

Your friend doesn't know what they're talking about. It's hydrogen.

Default117 (author)Tombini2009-03-15

Yeah... I mean no... I mean... Aww crap Your making me think XD

ReCreate (author)Default1172009-03-18

{{{ }}}
brain explodes

nodrog19 (author)ReCreate2009-05-01

Equal amounts (by the mole) of gas at the same conditions have equal volume. You will get 2 volumes of H2 and one volume of O2. Look up the ideal gas law.

ReCreate (author)nodrog192009-05-01
Everything now explodes,including brains
marmique123 (author)ReCreate2010-02-09


yep , 22,4 liters of gas / mole

Moles are furry and cute.

digital01 (author)professorred2009-07-07

No they are curry and fute

professorred (author)digital012009-08-13

MMmmm. Mole curry.

bylerfamily (author)ReCreate2009-08-13
brain explodes.

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Bio: Gimme a break I'm only 14
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