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Author Topic: Why do steel electrolysis electrodes make a solution brown?  (Read 2212 times)

Robert

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Robert  asked the Naked Scientists:

Hi Chris,

I made a hydrogen kit myself using two stainless steel round round head bolts for posts suspended in my water tank running off my 12V truck system.

Resistance between the stainless steel post suspended in water was very high. I kept the two post separated by a piece of plastic.

While on vacation I used the system with marginal results but my question has to do with the water turning a rusty brown after a few hours use; do you know what could have caused this?  

Thanks  Robert

What do you think?


 

Offline Madidus_Scientia

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Why do steel electrolysis electrodes make a solution brown?
« Reply #1 on: 11/07/2008 14:37:28 »
That would be the iron oxide being produced at the anode.
« Last Edit: 11/07/2008 14:45:39 by Madidus_Scientia »
 

Offline chris

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Why do steel electrolysis electrodes make a solution brown?
« Reply #2 on: 12/07/2008 12:08:12 »
Hi Robert

the reason is that you are dissolving the positively charged electrode, liberating iron 3+ ions (iron III) into solution. As iron III ions are brown, your solution is changing colour.

This is happening because at the positive electrode metallic iron atoms are giving up electrons to become soluble ions. At the negative electrode, where there is an excess of electrons and you might expect the reverse to be happening, the electrons are mainly picked up by hydrogen ions (H+) to form H2 gas, because this is more energetically favourable than producing new metallic iron.

Chris

 

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Why do steel electrolysis electrodes make a solution brown?
« Reply #2 on: 12/07/2008 12:08:12 »

 

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