chloric1
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Salt Bridge
Hello all! As I type this I have a salt bridge diaphram cell running. OK I want to know how long should it take to charge the diaphram with ions.
Here arethe stats of my cell.
My "salt bridge" is an ordinary clay pot that holds just uner 500 ml. This is inserted in the center of a 5 L tupperware. The electrolyte
is MgSO4 between 6 and 8%. There is about 3L anolyte outside the cell
and there are two lead electrodes with about 10 cm sq each. THe cell votage is about 12VDC with 6 AMPS. The clay pot has typical wall
thickness(about 1/8 inch)
Anybody built simular cell?
Thanks for your input
Fellow molecular manipulator
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Marvin
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I dont understand what you are trying to do. Ions will leave the cell at the same rate they enter is (in this case becuase the charges are the same).
Lead does not make good electrodes, and the salts formed can be very toxic though in the case of sulphate I dont think you are in much danger. If
your anolyte and catholyte are difference you can get a sort of electrically increased ion diffusion.....
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chloric1
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My experiences
OK Marvin, here is the scoop. I was not set out to make an end product just merely to try out a method with store bought materials. I have heard
about using flower pots as a diaphram but I was skeptical. I thought they would be too thick or they would react with the electrolytes. But, one day
I decided I would just try it to see if I had a use for it. I did "charge" the diaphragm with epson salts and lead electrodes. It worked
nicely to just have a working set up. By the way lead can make good electrodes when used in a sulfate medium. In fact as a nice bonus I got a
coating of lead dioxide on my positive(anode). In fact many industrial processes uses lead electrodes when they were seen as benificial.
Example,oxidizing trivalent chromium waste back into hexavalent chromium for organic synthesis. Obviously you would not want to use lead electrodes
in strong alkali, nitrate, or halogen electrolytes but they still can be useful in many applications.
Also, once I had a charged salt bridge, I made a NaCl electrolyte with a nickel cathode and a iron anode. the anode was in the flower pot and after
11 hours at 2 amps it disappeared!! I had a green solution of ferrous chloride with some rust floating in it(easily filtered) and it was noticeably
hotter that the catholyte which was mostyl NaOH! I verified this becuase I dumped some of the green liquid into it and got the characteristic blue
green Fe(OH)2!!!  Now obviously this proved to be quite an adventure and I would guess that I could find this quite useful.
Oh and if I made my own NaOH or KOH this way I can easily purify them by dissolving them in ethyl alcohol to separate any NaCl impurity.
[Edited on 10/31/2003 by chloric1]
[Edited on 10/31/2003 by chloric1]
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Marvin
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Useful information, but unless you need a lead electrode for a purpose only it can do, its a bad idea to be using it. Ive made copper nitrate in a
similar idea to your ferric chloride, though I used a paper salt bridge.
I'm still no closer to understanding what you mean by 'charging' a salt bridge though.
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Al Koholic
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I think what he is trying to convey by "charging the salt bridge" is that he first soaked the pottery pot in a magnesium sulfate solution so
as to impregnate the matrix with ionic solution. I don't see why this would be necessary though because the same thing will happen once you
actually set up the experiment with the electrolytes anyway.
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Saerynide
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chloric1, I got kind of interested at your little experiment that made Fe(OH)2. So I decided to try it out at home, except I didnt have a salt bridge
cause I dont have something that could act as one (I did this in a cookie jar btw).
I used an iron anode and a nickel cathode and a NaCl solution. Only, I didnt get much Fe(OH)2, but I did get quite a bit of Fe(OH)3 though. It looks
like I got a load of Fe0 cause theres all this black precipitate with only tiny amounts of greenish blue Fe(OH)2.
So, is there no other way to make Fe(OH)2 (i dont want Fe(OH)3 cause it doesnt look as cool, its not green! ) other than to use a salt bridge? I was thinking that I would get Fe(OH)2 at the bottom of the NaCl solution.
[Edited on 23-11-2003 by Saerynide]
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unionised
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Fe(OH)2 is not stable in the presence of air. You could swap the electrodes and hope to get Ni(OH)2 which is stable and green.
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Saerynide
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Before conducting the experiment, swapping the electrodes had crossed my mind, but I was afraid of dealing with the nickel hydroxide's toxicity
and carcinogenicity. I think Id rather not risk it.
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unionised
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Can't say I blame you. I gather there is a nice bright green copper arsenate. 
This thread seems to have drifted from the original topic.
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