jhonn
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Chromate /dichromate substitute in chlorate cell
Does anyone knows if there is a substitute for chromate/dichromate in a chlorate cell ? I'm using MMO anode and titanium cathode, the cell works very
well, but i want a higher efficiency, but do not want to deal with Cr+6.
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woelen
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The amount of hexavalent chromium needed in a cell is low and you hardly have to fear its toxicity. In a cell of a liter you can use 200 mg or so and
that is enough. You do not even have to handle pure dichromate. If you have chrome alum or chromium sulfate (either the dark purple stuff or the green
stuff), then dissolve some of this in water, add a slight excess amount of bleach and add the resulting yellow solution to your electrolysis cell.
An alternative to adding chromate or dichromate is adding fluoride, but this makes construction of the cell much more complicated. Fluorides attack
glass and even in low concentration they are VERY dangerous for the skin!! You also need to refrain from using titanium when you use fluoride as
alternative for chromate, because fluoride ion very easily corrodes titanium.
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jhonn
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Quote: Originally posted by woelen  | The amount of hexavalent chromium needed in a cell is low and you hardly have to fear its toxicity. In a cell of a liter you can use 200 mg or so and
that is enough. You do not even have to handle pure dichromate. If you have chrome alum or chromium sulfate (either the dark purple stuff or the green
stuff), then dissolve some of this in water, add a slight excess amount of bleach and add the resulting yellow solution to your electrolysis cell.
An alternative to adding chromate or dichromate is adding fluoride, but this makes construction of the cell much more complicated. Fluorides attack
glass and even in low concentration they are VERY dangerous for the skin!! You also need to refrain from using titanium when you use fluoride as
alternative for chromate, because fluoride ion very easily corrodes titanium. |
You mean to use the bleach to oxidise the the Cr+3 to Cr+6 ?May i add the Cr+3 source directly to the cell, since there is constant formation of
hypochlorite in the cell, and the small ammount of Cr+3 wont interfe in the chlorate production.
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Fantasma4500
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i believe that the dichromate / chromate actually helps controlling the pH of the cell aswell as stopping a chemical reaction (somewhat advanced, cant
remember it in details) that makes the NaClO go into useless stuff, degenerate at the cathode somehow..
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