[kwhubby]

Hi, I am building a good sized homemade hoffman apparatus out of pvc pipe in order to decompose water to hydrogen and oxygen and contain the gases for use. I need help to find a decent electrolyte and decent electrodes as I am having difficulty finding something that doesn't disolve the electrode rapidly, cause unwanted reactions or cost me a fotune. I hear sulfuric acid as an electolyte and platnum for electrodes will function the best, but I want to find something cheaper and easier to get. I heard nichrome wire and sodium sulfate was good, so I got some of this to be disapointed. At first it appears to function but then the oxygen electrode stops producing oxygen gas and disolves creating yellow stuff in the water. I heard graphite does well, this works but seems to quickly disolve the graphite and puts a bunch of black stuff in the water. I did an expirament with a piece of stainless steel for the oxygen electrode and this appears to work well without disolving but I did not do a long test (I only tested for about 10 minutes) to truely see if it will work very long. Thanks for any *delete me*  

[Mitch]

Graphite electrodes will work as well as platinum. Much cheaper too.

[kwhubby]

Ok, thanks but I assume that this requires a better graphite as the pencil lead I tried breaks down rapidly. If you know where and how I could get suitable graphite electrodes that would be nice, Ive heard some batteries (I think the 6v lantern "heavy duty" batteries) have graphite electrodes in them maby I could open a battery to get these. I think I may do some more expiraments and test to see how far the pencil graphite and stainless steel will break down over time. My hoffman device will hook up to a water hose for an easy way to compress the gas for filling things such as balloons, because of this I have it set up with a somewhat permanent system and it will be difficult to replace the electrodes. I should see if I can get some threaded pvc fittings to make it easier to replace electrodes.

[Corvettaholic]

I believe you can get some nice thick carbon electrodes from www.unitednuclear.com, or you can try a welding shop. They usually have some available.

[kwhubby]

I could not find those carbon electrodes on that website, maby I didn't look at the right places I ran a test with stainless steel for about 4 hours using 20 volts running at about 2 amps. I found the stainless steel did not appear to have corroded and still measured 0.0 ohms of resistance on my multi meter. The only noticeable difference was the stainless steel was a bit less shiny, but I believe this was due to the fact I was using cheap stainless steel forks that probobly had some layer on the outside making it shinier. I think I will just use stainless steel, maby I will get some better grade stuff somewhere. The one thing that I am very curious about is what happens to the water. At first the water gets yellow then brown matter starts to build up, I wonder what reactions are occuring besides producing oxygen and hydrogen what is this other stuff in the water? (I am using sodium sulfate and water)

[billnotgatez]

http://www.scitoys.com/scitoys/scitoys/echem/echem.html

[kwhubby]

Ah! interesting that confirms the cheap batteries as sources for carbon electrodes. I am trying my stainless steel idea but then I think will go with carbon from batteries or gold plated electrodes. I assume the gold will work the best as it won't oxidize or break down. I wonder if the gold plated things will have some wierd plateing type issues that will expose the metal underneath and cause oxidation, or if the carbon electrodes will create CO2 instead of oxygen.
 I just noticed that site sells platnum coated nickle wire for 10$ a foot, I might just buy two feet or so of that stuff and use that!! still cheaper then those stupid gold plated speaker connectors at radio shack.

[billnotgatez]

Platinum Wire might be more expensive now - I am not sure how current the site I posted.

[billnotgatez]

<http://www.sciencelab.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=10-500>

<http://www.sciencelab.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=10-501-2>

<http://www.sciencelab.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=10-498>
<http://www.sciencelab.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=10-499-2>

[tony]

Hi,
The best electrode i have found is 316 stainless steel, in potassium hydroxide only (NOT draino etc!) the other materials just get eaten away. there is alot of misleading project information on the net.
I have done substantial testing but dont claim to be an expert - yet! - visit my webpage here:

http://pulse8.i8.com/h2o.htm

I have decided to post my hydrogen/oxygen gas project and results to that others in this area may benefit from it. Also learn how why and what not to do...
My current project 3 is underway, and I hope to update when finished.
thanks, let me know if it is helpful, so that I may judge interest and keep inspired to update more.
tony

[billnotgatez]

tony –

I read your web page and found it interesting. It is nice to see the kind of experimentation you are doing.

A question I have is how did you determine you have pure potassium hydroxide solution from the filtration of wood ashes. One wonders if there are also other soluble inorganic and organic molecules in the solution. In any case I guess it makes no difference if the impurities have no effect on the electrodes or the gas production.

[cavemen]

I have the same problem.
The only thing I am concerned about is that in both stainless steel and aluminum, the corrosion is prevented by passivation.

Wouldn't stainless steel erode due to exposure of iron from the chromium protective layer?

Would aluminum work?

Brass?
Nicker?
Tin?

Lead?
Copper?
Chromium?

Any other fairly popular metals?

I am building a Hoffman apparatus.

[billnotgatez]

You could make a small system cheaply and test the metals you suggest. But, I have seen many experiments try copper only to find it becomes part of the water solution giving a green / blue tint. Brass has copper in it. My guess is many of the other metals you listed would erode quickly.

[Arkcon]

Like they say at the top of this thread you've raised from the quiet dead cavemen:, you can substitute graphite pencil leads for platinum, but like billnotgatez: says, your metal choices aren't much better than each other -- they will be attacked by electrolytes, or consumed by the active oxygen before it becomes O₂ gas.

[ARGOS++]

Dear Caveman;

Tony is quite right as the Book: "Chem. Schulversuche” ( = School-Experiments) is telling.
In case you, like Tony, use diluted NaOH  as the Electrolyte, you can also use Nickel, or Nickel-plated Copper.

Nickel-plated Copper ( ~10 μm) is used in the “Cheapest” Hoffman-Apparatus you can see below.
(Plating you can easily do in Nickel-Sulfate by yourself.)

Good Luck!
                    ARGOS⁺⁺