NEMO-Chemistry
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acid Suggestions for a chlorate cell
I dont want to shoot my mouth off too early, but while trying to get something else to work i came across a recent journal article.
Using what they suggested as electrodes it has/is working really well for another application, I cant set a Chlorate Cell up for a week or so as it
would mean rebuilding my old one.
However there might be a slight problem, normally i put a little HCl in the cell and some Dichromate as per Woelens page on Chlorate cells.
The problem however is the electrodes contain Nickel, so I assume even with an alloy of 7-8% Platinum in the conditions in the cell would attack the
electrodes.
So apart from Nitric,Sulphuric or Hydrochloric acids, are there any other acids that can be used to lower the PH of a chlorate cell and wont attack a
Nickel alloy?
If it works then we have access to extremely cheap (normally free) pretty big electrodes that should last.
Sorry if its a bit cryptic but I want to try it before shouting out, or getting shot down in flames. The electrodes are currently being used for
something else and working extremely well, i modified the procedure used in the journal a little bit and now they work exceptionally well.
Having recently been trying to dissolve Nickel flakes in Ferric Chloride acidified with HCl, i am reluctant to try a Chlorate cell with HCl in and a
powerful oxidizer.
But if we can up with another acid that isnt to harsh on a nickel platinum alloy then we might have decent chlorate electrodes.
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walruslover69
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Fair warning, I do not have that much hands on experience with electrochemistry. But you might be able to use phosphoric acid. Nickel Phosphate is
insoluble. It might cause a problem with passivating your electrode though. Using some acid transition metal salt like FeCl3 might also be possible
but my intuition says that would cause problems.
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NEMO-Chemistry
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Quote: Originally posted by walruslover69  | Fair warning, I do not have that much hands on experience with electrochemistry. But you might be able to use phosphoric acid. Nickel Phosphate is
insoluble. It might cause a problem with passivating your electrode though. Using some acid transition metal salt like FeCl3 might also be possible
but my intuition says that would cause problems.
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Its not about being insoluble, you dont want the electrode to be affected in the first place, i thought the Dichromate was used to stop passivization?
I will give them a try with HCl anyway, but I need to build a different type of cell to the one I got, what i really like about these is the size, you
can get two different sizes and both have very good surface area.
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walruslover69
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From reading woelen's method it appears the chromate forms a very thin film over the electrode preventing the reduction of chlorites. Being insoluble
means that its not going to dissolve your electrodes. I would recommend using a week acid to acidify with. If your electrodes are being attached by
acid, using a weak acid will slow it by at least an order of magnitude compared to HCl. Phosphoric acid being triprotic will also keep your solution
acidic 3 times as long given the same molar amount.
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NEMO-Chemistry
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| Quote: Originally posted by walruslover69 | | From reading woelen's method it appears the chromate forms a very thin film over the electrode preventing the reduction of chlorites. Being insoluble
means that its not going to dissolve your electrodes. I would recommend using a week acid to acidify with. If your electrodes are being attached by
acid, using a weak acid will slow it by at least an order of magnitude compared to HCl. Phosphoric acid being triprotic will also keep your solution
acidic 3 times as long given the same molar amount. |
Ok great thanks for explaining. Even HCl seems to take a while getting to Nickel, plus this is an alloy of not just Nickel and platinum.
I will have a got at the weekend with some different acids, fingers crossed it works  .
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markx
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I would suggest to try it without the acid and chromate and see how the system behaves, Especially if you have the suspicion that the acidification
may cause harm to the electrode material. Perhaps the system shall perform just as well without the additives.
In my experience one can usually get quite decent yields from small scale chlorate cells without pH control and chromate for the inhibition of
parasitic cathodic reduction.
Another way to improve yields without pH control is to use asymmetrically dimensioned electrodes (cathode surface area smaller than anode). If I
remember correctly Varmint had great success with this method using small titanium rods as cathodes.
Exact science is a figment of imagination.......
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