Rhodium
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About chlorate cell electrodes
Hi guys!
First of all I'm very sorry for my bad knowledge of the english language^^
Secondly there is my problem.
I want to build a chlorate cell.
Normaly some sodium chromate is added du build a 'wall' of chromium oxide in order to prevent a cathodical destruction of the chlorate. Could you
reach by using chromium or something with a layer of chromium as cathode the same effect?
As anode platinium coated stuff was used.
The goldsmith told me that they can't coat something with platinium but rhodium. So should I search a ney goldsmith, or will rhodium work as well (I
think the thin layer won't make some big price diffrence) ?
Thanks in advance
Rhodium
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garage chemist
chemical wizard
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Dont use precious metal coatings for the anode, they will be slowly attacked, and then the base metal will be attacked much faster destroying the
anode.
Use graphite, its cheap and if you keep current density low and temperature below 40°C erosion will be small.
The acthode will not dissolve, you can use almost any metal for it.
That does also mean that chromium will not go into suoltion at the cathode, and certainly not as the required chromate/dichromate.
You should really add a chromate or dichromate to the cell liquor, it vastly improves the efficiency because it prevents reduction of chlorate back to
chloride at the cathode.
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woelen
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Making some chromate is not that difficult. You do not even need to isolate the chromate, you only need a very small amount for an electrolysis cell.
One method is to use chromium oxide from a pottery/ceramics supplier. Mix this with some NaOH and melt this. The chromium oxide dissolves and now it
is converted to a water-soluble form. If you have an oxidizer like KNO3, then add this to the melt. It will change color from green to yellow and you
have your impure K2CrO4. This can be used as is in your cell, just dissolve it in water and add HCl such that pH is close to 7 (not critical at all).
200 mg or so of chromate/dichromate is suitable for an average chlorate cell.
If you can obtain chrome alum, then life even is easier. Dissolve 500 mg or so in some water and then add a solution of NaOH. First a precipitate is
formed, but you should add more NaOH-solution, until the precipitate dissolves again and a nice clear green solution is obtained. Then add a little
more NaOH-solution, amounts again are not very critical.
To this green solution, add 10 ml of 3% H2O2, and carefully heat (do not boil). The liquid will turn yellow (with some green or brown hue, but that
does not matter). Once the liquid is clearly yellow, then heat vigorously, such that the liquid boils for some time. This destroys any excess H2O2.
This liquid then is roughly neutralized with HCl and then it can be used for an average chlorate cell.
As garage chemist says, graphite is easy and cheap. Best is to use large rods. Nice rods, which are easy to obtain are the ones from 4R25 batteries:
Example: http://www.batterybob.com/product.asp?intProdID=682958
These batteries are cheap, and it really is nice if you can obtain used ones for free. This type of batteries is available in many agricultural shops,
or the better equipped hardware stores.
For some practical experience, see my webpage on bromate-making. Chlorate-making is very similar, except that stirring/dissolving the chlorine is
somewhat more critical:
http://woelen.scheikunde.net/science/chem/exps/KBrO3_synth/i...
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vulture
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Please! We've got plenty of threads on this matter.
Closed.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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