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Chromate removal from a Halate cell

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I`ve just been experimenting with a Halate cell, in particular Calcium Chloride.

80ml of saturaled calcium chloride was added to 350ml of water and 50ml of 20% HCl, and a pinch (1/4 spatula) of potassium dichromate added.


I`m keeping the cell started as acidic so so Calcium hydroxide doesn`t form and insulate the carbon electrode.


anyway, the Cl2 smell was really bad, so I added a little H2O2, instantly the soln turned Purple/black, Very strange I thought but let it continue.

slowly over a period of roughly 2 mins the soln got lighter and lighter purple leaving an Aqua colored soln and perfectly clear.

now there`s a purple PPT floating on the top that will be Very easy to filter off later :)


now this thread isn`t about how good bad and idea this was for making a Chlorate cell! it was Purely experimental, so stay to topic here.


this thread IS about removal of the Chromate after a cell is completed, it Should leave a cleaner product without so much Chromate contamination :)

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YT, did you really add HCl to the chlorate cell? That is absolutely not good. It prevents formation of chlorate, because the reaction of making chlorate requires hydroxide.


Adding dichromate to the cell is a good thing, but removing it is really hard, if you use carbon rods for the anode. I have found out that the carbon anode gives off tiny particles of carbon, which adsorb some chromate and/or chromium(III). These carbon particles are so small that they cannot be removed easily.


If you, on the other hand, use a platinum anode (and the cathode can be any metal), then the product is really clean, and also remarkably, the chromate can be removed VERY easily. It simply does not get included in the crystal lattice of the halate formed. So, it is the combination of carbon and dichromate, which makes such a mess.

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well the odd part is that it`s PH sensitive, the cleanup only seems to work at a low PH and also seems to need the electricity to form the purple ppt.

I tried replicating this in test tubes, using CaOCl as one of the tests, actualy got chromate colors that I never knew existed :)

AND the reactions with H2O2 change color over time! :)

the cell`s working fine now anyway, I just reverse the current when it starts to slow down, and filter paper dip and dry test seems to show that`s working well as an oxidiser, only problem is that some of the yellow/orange dichromate has come back into soln.



try every single combination of dichromate soln and H2O2, HCl, and CaOCl.

the results are Fascinating!

but you Must give a few mins before the addition of another chem as that gives the existing mix/combo time to react and change.


I recon with a little tinkering, it may be possible to make a Really Vivid oscillating reaction :)

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