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Author: Subject: AP from table salt. Not in my case.
Cornz
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sad.gif posted on 30-9-2021 at 06:10
AP from table salt. Not in my case.


Hi all.
Ok, i'm trying to make a small amount of AP and this is how
Non iodised sodium chloride.
Platinum anode Titanium cathode
6-7v 10 amps for 8 days topping up with water as needed due to evaporation.
NO perchlorate (tested with methylene blue).

Re ran, different salt (still sodium chloride, no iodine) at6v 30 amps for 3 days.
NO perchlorate.

Of course , at this stage i haven't added the ammonium chloride to displace it but shouldn't i have a sodium perchlorate solution and shouldn't my MB react?


MB is good, same cell with an MMO anode and potassium chloride produces potassium chlorate easily (plat anode is from same seller so assumed genuine) which i then thermally decompose to potassium perchlorate and MB reacts correctly by turning pink and clumping.

What am i doing wrong?

Tried with a water jacket (30 oC) or without 70oC. Tried two different salt brands, two different currents and i just cant seem to get any perchlorate.
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dettoo456
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[*] posted on 30-9-2021 at 07:50


You might be suffering from too high of a current density and/or a too dilute electrolyte solution. The cooling for your cell acts as a twofold measure; keeping the cell from overheating, and letting the cell run a little warm to keep a saturated salt solution. Also on the current density, I’m not sure what the recommended amp/cm^3 level is for NaClO4 but if you have a ton of water loss then that might be a problem due to too high power. Last, iirc, AC favors cleavage of H2 and O2 while DC is more direct to bleach and eventually perchlorates (correct me if I’m wrong though). DONT solely take my advice though, look around the board for more info. Keep your workspace well ventilated too, you really don’t want an HHO lab detonation.
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Cornz
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[*] posted on 30-9-2021 at 08:28


Quote: Originally posted by dettoo456  
You might be suffering from too high of a current density and/or a too dilute electrolyte solution. The cooling for your cell acts as a twofold measure; keeping the cell from overheating, and letting the cell run a little warm to keep a saturated salt solution. Also on the current density, I’m not sure what the recommended amp/cm^3 level is for NaClO4 but if you have a ton of water loss then that might be a problem due to too high power. Last, iirc, AC favors cleavage of H2 and O2 while DC is more direct to bleach and eventually perchlorates (correct me if I’m wrong though). DONT solely take my advice though, look around the board for more info. Keep your workspace well ventilated too, you really don’t want an HHO lab detonation.


Thanks. I don't think the electrolyte is too weak, its as saturated as i could get it.
I have been using DC in both instances, wonder if that could be the issue. That's something to look into.
Talking of hydrogen, obviously, a lot is produced, which i knew so was venting it outside. So as a bit of an experiment, i captured some and did the old light a splint trick. So, a few weeks later i'm making a bit more and i think, lets try that again, only this time, like a pillock, i put a light to the end of the vent hose. BIIGGAA BADDAA BOOOOM!!!! Blew the plastic lid straight off the top of my cell into pieces and made me realise why the Hindenburg was a bad idea!!
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karolus28
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[*] posted on 30-9-2021 at 09:08


in this video they mention persulfates https://www.youtube.com/watch?v=cxmuHoh7ObM, I have no knowledge on the subject but I suppose it's worth checking this out



Hi, please read about exif data.
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Microtek
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[*] posted on 1-10-2021 at 12:47


Do you adjust the pH? IIRC, you need to keep it slightly acidic (usually by periodically adding hydrochloric acid).
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Cornz
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[*] posted on 2-10-2021 at 00:21


Quote: Originally posted by karolus28  
in this video they mention persulfates https://www.youtube.com/watch?v=cxmuHoh7ObM, I have no knowledge on the subject but I suppose it's worth checking this out


Thanks, i had seen that but sort of dismissed it, however, he is using DC so i know thats unlikely to be the problem.
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Cornz
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[*] posted on 2-10-2021 at 00:27


Quote: Originally posted by Microtek  
Do you adjust the pH? IIRC, you need to keep it slightly acidic (usually by periodically adding hydrochloric acid).


Hi, thanks. No, i haven't. Don't have any HCI but have seen a proccess for using brick acid (Muriatic acid which i believe IS HCI) and a container of water, the Muriatic acid fumes "move" over to the water turning it over a period of weeks into reaction grade HCI.
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Microtek
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[*] posted on 5-10-2021 at 02:59


Yes, muriatic acid is another name for hydrochloric acid. If you are concerned about the purity of the acid, you can distill it, but you will need an efficient condensing setup. If you have access to dilute sulfuric acid, you could react it with NaCl, and distill. Just be aware that HCl is a gas with limited solubility in water, so if you use concentrated sulfuric acid you will produce lots of very corrosive and harmful gas. If you can make a good absorber coloumn, you can produce your hydrochloric acid this way.
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markx
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[*] posted on 6-10-2021 at 01:15


So you are trying to go from sodium chloride to sodium perchlorate with a Pt plated anode. Give it time to work...a week shall do nothing in terms of perchlorate when starting from chloride. It rarely does even when one starts with a "ripe " chlorate solution.

Do not push the cell to high amps by turning up supply voltage potential, just keep it ticking along quietly for a few weeks and then recheck. Pt shall produce perchlorate very nicely below 5V of cell potential and at low current densities. High currents achieved by cell voltages over 5V provoke excessive wear of your anode and it shall fail due to passivation.

I've messed around with enough Cl->ClO4- conversions to say that it is best to leave it at peace and ticking along quietly at minimum cell voltage that are required to achieve a sustainable current (5-12A is plenty for that stage if we are talking about a 1-3l cell). Do not go over 5V with the cell voltage....that usually guarantees a quick end to the positive side of the cell.
In my cases it took about a month to complete a conversion of fully loaded (2L if I remember correctly) cell. Perchlorate formation on Pt is not really a straightforward process in practice, there are delays and "hickups" that can reach several days of duration before any ClO4- begins to form in a chlorate enriched electrolyte. So just give it ample time and keep the conditions mild to preserve the electrode.
Also do not use any other grades of Ti than CP (commercially pure) for the anode stems or other parts of the cell. Alloyed grades are not durable enough and shall corrode, creating a huge fluff of precipitate.




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B(a)P
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[*] posted on 6-10-2021 at 06:03


You might have better results going to chlorate, then purifying, then go from pure chlorate to perchlorate. There are some differences between what is optimal for a chlorate vs perchlorate cell, so it is good to know which stage you are at to maximise efficiency.
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yobbo II
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[*] posted on 6-10-2021 at 12:32


http://pyrobin.com/files/ChloratesAndPerchlorates.zip

This will explain it if you want to read up.

Yob
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Metacelsus
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[*] posted on 7-10-2021 at 03:13


Yes, I agree it would be better to go to chlorate first (perhaps using an MMO anode) and then do the final oxidation to perchlorate. This has worked in my experience.



As below, so above.
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Cornz
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[*] posted on 16-10-2021 at 09:29


Thank you all for the help.
When i resume my testing i'll post the results.
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phlogiston
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[*] posted on 16-10-2021 at 13:13


How big is your cell (electrolyte volume)?
Have you calculated how much Ah is necessary for the conversion, and compared it to how much you actually put through the cell?




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mysteriusbhoice
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[*] posted on 5-11-2021 at 12:29


theres some sort of lag in the conversion of chlorate to perchlorate due to pressence of residual chloride and hypochlorite in the liquor at 99% chlorate conversion. This can be fixed by adjusting the pH to 7 with HCl, H2SO4 or persulfates which will help kick out the chloride and hypochlorite converting it to chlorate. I usually operate perchlorate cells above 200ma/cm^2 with a max of 250ma/cm^2 and the voltage around 5 volts.
The thing most people dont do is design the cell such that the current density at 5 volts will be around 250 or higher which can be done by reducing the gap of the anode and cathode distance to something like 0.9cm or 0.5cm to which chlorate even operates at 200ma/cm^2 at 3.8 volts which is nice and helps with efficiency as it reduces power consumption. Once the chloride is all consumed the real start point of the run from chlorate to perchlorate will begin and it ends when the cell starts to pump out ozone which is noticeable. be careful of the spontaneous detonation of H2 and ozone when you run a cell at around 40 amps which happened to a friend using a PbO2 anode.

After the run you have to destroy any remaining chlorate in the perchlorate which can be done with the usual stuff like SO2 and acids or what I use is UVC lamp for 2-3 days and HCl as a catalyst which releases O2 and regenerates HCl which after boiling down the solution to remove remaining chlorate then neutralizing it with sodium carbonate or ammonia solution.

[Edited on 5-11-2021 by mysteriusbhoice]
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