Water electrolysis?

[MDJH]

I know I've asked about this before, but I was thinking of how to do water electrolysis in a reasonably efficient and/or relatively inexpensive manner.

 

One idea I had was to set up a bucket, throw in some epsom salt (my current bag of epsom salt doesn't specify whether it's the heptahydrate or some other concentration of it though) and add tap water and stir until it's either all or mostly dissolved. Then I'd put in a couple plastic or glass bottles, (one about twice the size of the other) immerse them in the solution until they are filled, then find some way to fasten them upside-down (ie. the open end is facing downwards) and have electrodes set up so as to be insulated outside the bucket, on its way into the bucket, and just about everywhere except either inside the bottles or just below such bottles (preferably the latter, so long as the bubbles would go into the container, since I'd like both bottles to be filled with their respective gases) and connect said electrodes to a power supply that would consist of a combination of AA and AAA batteries connected primarily in parallel, through means of one piece of aluminum foil across all their positive terminals, and another piece of aluminum foil across all their negative terminals. This raises a few questions:

 

1. How long would it take epsom salt to either reach saturation or get fairly close to it? I ask this because with an unspecified concentration, I wouldn't know how concentrated the epsom salt would be until I brought it to near saturation through stirring, but I wouldn't want to assume too soon that the epsom salt was saturated.

 

2. A related question, how much voltage does it take to drive electrolysis with epsom salt as the electrolyte, and to what extent does it depend on the concentration?

 

3. And related to question 2, how would the current be drawn if the batteries are connected in parallel? Would it draw a variety of voltages (ie. from varied effectiveness of the batteries) or would they average out? Would the current be drawn as if each battery-water-battery loop were its own circuit, or as if the combination of batteries were an average power source and the water was the resistor?

[ercdndrs]

Unfortunately I can't accurately answer your questions, but I have some things I'd like to point out.

 

1. If you want to do this efficiently/ inexpensively, batteries aren't the gratest choice. I use a car battery charger, preferrably with a low (~2V) voltage/high current setting.

 

2. make sure you use an inert anode, or you'll have a metal sulfate, magnesium hydroxide, and H2 gas forming instead of H2 and O2.

[MDJH]

Unfortunately I can't accurately answer your questions, but I have some things I'd like to point out.

 

1. If you want to do this efficiently/ inexpensively, batteries aren't the gratest choice. I use a car battery charger, preferrably with a low (~2V) voltage/high current setting.

 

2. make sure you use an inert anode, or you'll have a metal sulfate, magnesium hydroxide, and H2 gas forming instead of H2 and O2.

1. Car battery charger? Where could I get one?

 

2. Inert anode? Like graphite?

[rogerxd45]

i use an old laptop power supply that is 18v and about 5 amps. which is easy to get from a friend, also if you buy an external hard drive and take it apart and put the hardrive inside your computer you will have a left over power supply very similar to the lap top one.

an old desktop power supply would probably work well also but they require some rewiring to get them to run outside of a computer. which can be dangerous if you dont know what your doing.

however i dont know if these are optimum due to there high power consumption...its what i had so i used it

 

you can buy a 6v lantern battery (carbon-zinc not alkaline) take it apart and you have 4 carbon electrodes in the center of each cell that already have a wire attached to it.

 

 

i also dont think you need to get it fully saturated with an electrolyte either. unless im trying to create chlorine gas (using NaCl) then i just add a little bit

 

someone else can probably clear up some of the gaps i left.... thats just the set up i came up with with what i had on hand.

 

also keep in mind as your bottles fill up they will start to float and more gas will escape unless you have them held in place

[HaydenHatTrick]

just btw, you want to use Sulfuric acid as your electrolyte, for it doesn't take part in the reaction (like salts)

Graphite is a good electrode

Distilled water has less crap in it (just saying)

If you separate the anode and cathode so the gas collects in different containers, then you get each gas in its pure form (however I wouldn't suggest breathing either of them!!!)

[Fuzzwood]

Epsom salt won't take part in this reaction either. Sodium won't reduce or oxidise, nor would the sulphate at room temperatures.

[Ahamed]

When u use NaCl as electrolyte u will have to use platinum as electrode which wud be v expensive maybe..

Actually.. can we use graphite as electrode and use any solution that produce H+ and OH- as electrolyte?

My blog: http://globaltutor.blogspot.com/

[John Cuthber]

If you are using 12 or 18 volts to electrolyse water then you are wasting a lot of power. The cell voltage is about 2v and the rest (10 to 16V) is wasted heating the electrolyte.

 

Fuzzwood, I don't think you meant sodium.

[UC]

Epsom salt won't take part in this reaction either. Sodium won't reduce or oxidise, nor would the sulphate at room temperatures.

 

Epsom salt is Magnesium Sulfate heptahydrate.

[Fuzzwood]

Epsom salt is Magnesium Sulfate heptahydrate.

 

Thank you, even better, magnesium won't reduce either. So why would you want to use sulphuric acid as an electrolyte?