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markx
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Not that it is false to use higher voltages, but unduly harsh on the anodes in my experience. The industry aims for max yields and productivity and
hence perhaps the high voltages are advocated and have settled in the model as a dogmatic element. I also got the strong theoretical pre-experimental
impression from literature that one needs above 5V of cell voltage to even enable the formation of perchlorates....does not seem like it really after
the experiments I ran and the yields I got.
The practical approach that I took after burning some anodes real quick at high potentials was to limit the cell voltage to the minimum that still
enables reasonable current flow through the system. Reasonable being on the order of about 7-10A for a 3L cell at the perchlorate stage in my case.
This was achievable below 5V. The simplified reasoning being that if side reactions that occur on lower anode polarisation levels (lower current
density due to lower cell voltage) hinder the formation of perchlorate synthesis then at higher polarisation they shall be further increased and thus
not much shall change except the electrode wears quicker due to new side reactions being called to life. Hence if reasonable current flow is enabled
then one has no need to push it further. Seemed to work for my purposes, but I do not claim that this is "THE RIGHT WAY" 
Everyone has got a different setup and different nuances....whatever seems to work in any particular case is fine. All that I'm advocating is that
"what works" might have a broader reach of parameters than that being claimed in many mainstream references.
Exact science is a figment of imagination.......
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ManyInterests
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Quote: Originally posted by markx  | | Quote: Originally posted by Alkoholvergiftung | Sometimes is the imposible possible. Sometimes Perchlorate emerge in alkalien cells. they think if the bubbles of gas on the anode and cathode mix and
stir together it can be formed there also (as an example). But an direct conversion on pt anode is an feat. 
[Edited on 28-10-2025 by Alkoholvergiftung] |
It quite consistently forms in alkaline cells according to my experience....I've done numerous direct full conversions of Cl- to ClO4- in single runs
with Pt coated Ti anode and Ti cathodes. No additives or pH corrections at any stage, just let it tick along at a minimum cell voltage which still
enables reasonable current flow (less than 5V), top up with water as required (or chlorate solution) and it usually works out just fine. The solution
after the ClO3- stage is quite alkaline, but it seems to pose no obstacle for further ClO4- formation. Nor does the residual Cl- content, since it
reaches an equilibrium concentration parallelly forming during perchlorate synthesis stage anyways (even if one was to start out with pure chlorate
solution). I've had no sudden passivation or other destructive events happening at the chlorate formation stage end. It just passes gradually over to
perchlorate synthesis and keeps on going. But as the ClO3- is depleted and the run nears the full conversion limit, the passivation can set in quite
suddenly and the anode gives up it's ghost. The same is true if one pushes the cell voltage past 5V. It steeply raises the anode polarisation and
intensifies competitive reactions (passivation or degradation due to excessive O2 formation e.g.).
Patience and time are your allies in this game....don't fiddle with the system nor push the cell to the limits and just give it time to do it's thing.
A month of constant running was about my realistic and repeatable pace for a full conversion of a 3l cell starting from chloride. Apart from adding
electrolyte to top off the lost volume I basically ran it unsupervised and it worked like a charm.
Just accept the fact that any anode beside a solid chunk of Pt is pretty much expendable when a near full conversion of ClO4- is required. One can
halt sooner and use selective precipitation and further purification to harvest the perchlorate and push a bit more life out of the anode, but
eventually it shall passivate or disintegrate (in a few runs). The conditions are way harsher than during chlorate formation which can be run
seemingly indefinitely with a MMO and some common sense. |
Your mention of patience is my take away. I think I've managed to stabilize my setup for now. Sure the current is far from ideal, but it is probably
the best given the circumstances. I will try to keep it running for a few weeks if I can to see if I can turn what I have mostly into perchlorate, or
at least have a decent amount of perchlorate in my run. I've recently been replenishing with both persulfate and additional chloride.
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ManyInterests
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I wanted to put this in an edit, but I couldn't. I want to put the results of my old run into the current run when replenishing the electrolyte. I
will obviously need more run time, but I am OK with that.
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ManyInterests
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I had to move my setup indoors with proper ventilation to protect it from the increasing cold outside. I realize that this does mean I can keep it
running for a good long time. So 30 days or more is not out of the question! I added all my previous run days ago and will just replenish with sodium
persulfate solution (I had added 225g of sodium chloride previously. I don't want to add any more).
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bnull
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| Quote: Originally posted by bnull | | Quote: | | Speaking of which what can I do about sodium chloride left over? |
I was preparing a perchlorate (or was it chlorate) cell the other day but didn't have a power supply that would work with the electrodes I was going
to use. I'll look into it and see what I can find. |
Quite late but...
Attachment: chlorates_and_perchlorates.pdf (3MB)
This file has been downloaded 64 times
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ManyInterests
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Thanks for the PDF. I will download and review later.
One thing I remember about removing chlorides is a lesson I learned from 2022... just hook up an electrolysis of with my solid IR-TU MMA (one that has
produced a lot of excellent chlorates and has a near 100% converstion) and just give it a run for a while, it'll turn the chlorides into chlorates,
which then can be put on the PbO2 setup to turn them into perchlorates.
Right now moving my setup indoors has done well to keep the temperature up and I worked to fix the corroding connections (and there is a lot of salt
creep developing) that is reducing the current. I was able to get the amperage up from a low 5-12 back to 21-17. Which should help things.
So far I have been running this cell for more than 3 weeks. I plan on at least 5 weeks now. I just hope that I will have mostly perchlorate by them
(or all perchlorates). I really want this to work.
My total run would include 725g of chloride + 480g of my previous run (a mix of chloride and chlorates with only a little perchlorate). I am
replenishing my electrolyte only with persulfate solution, not just distilled water. Or maybe I should be using just distilled water at this point?
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ManyInterests
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I am almost at my 5th week and I will be halting the synthesis this Saturday (November 29th). The amount of salt creep on the beaker and in the
container I put it in is unbelievable. Probably due to the mist that came out due to the heat, and that is what makes me want to get this done with. I
don't know if that stuff is chlorate or perchlorate (I am hoping the latter) which is why I intend to pour out the contents and filter out the PbO2
stuff that came out before boiling it. I will then dissolve the salt creep and filter out any insolubles before boiling that stuff down, too.
The electrolyte has been a lot clearer than before, too. I really hope I have a good amount of perchlorate at this stage, and I hope the salt creep
didn't result in too much loss. Keeping this indoors (there are no odors at all coming out right now) has done a lot to keep the temperature high,
which does help to encourage synthesis, but probably isn't doing my anode any favors.
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ManyInterests
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OK, so after halting everything and evaporating the water fully and grinding it up (there was a smell of chlorine as I did so, but it is gone now),
and I ended up with a yield of around 1240g. The burn rate is slow and with little residue, and I did three methylene blue tests. All used 1g of my
powder. The first was the least impressive and worst. I added too much water (30ml) and I used concentrated methylene blue and I only added an acid
(in this case 10% vinegar) in the end. Yes I was using an LLM and it was stupid. It did turn a strong violet though.
The second test was better, I added a few drops of sulfuric acid to 10ml of water with the powder in it, then another drop of of concentrated
meythlene blue. I also got a strong violet color that very slowly turned blue over 24 hours.
the third test had the same setup, except I diluted the methylene blue in 10ml of water (one drop in 10 ml) before adding a few drops of that into
another acidific solution, and this time it did dissipate purple slightly and it turned blue and remained that way for 24 hours.
Did I succeed? Do I have plenty of sodium perchlorate?
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Mister Double U
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Hello ManyInterests,
When I made Sodium Perchlorate many years ago, I was using roughly this route (has been 10+ years, so cut me some slack here):
Step 1: Electrolyze NaCl to make NaClO3.
I had a MMO anode capable of generating Oxygen - the ones which do not passivate.
I think I went to ~130% of the calculated run time and conversion was almost complete (explain in next step why I think that).
I also like to add the Faraday equation for calculating run time:
I * t = n * Z * F
I: Current [A]
t: Time [s]
n: Molar Amount [mol]
Z: Number of electrons needed for the reaction [e-]
F: Faraday Constant 96485[C/mol]
If you divide the equation by 'I' you get:
t = (n * Z * F) / I
Step 2: Boil down the cell liquor to a little bit more than saturation (I remember NaClO3 was very difficult to crystallize). Back then this was done
in a ceramic plated cooking pot. Boil the solution down to the point that a skin forms on the surface when blowing air on it and then maybe a little
bit more. If you stop too early, nothing crystallizes and if you get it right, a lot crystallizes. These 2 points are very close together (that was
very weird to me). Then place the solution in a freezer which goes to at least -10C. NaClO3 forms nice big cubic crystals. Some of them were measuring
~4mm on the edges.
Anyway, I do not think there was much NaCl left at the time, because none crystallized out at any time in the boiling down phase.
Lastly, I did the crystallization to purify the intermediate product. I was using self-made PbO2 electrodes at the time and I remember them being
quite sensitive to Cl[-] and [OH-].
Step 3: I ran the ClO3[-] to ClO4[-] conversion. PbO2 anode performed well without any brown stuff in the liquor - just some bigger pieces broken off
and at the bottom of the cell.
When conversion comes close to the end you will start to smell Ozone.
After that you let it run a day longer and take a small sample of the cell liquor and mix it with conc. HCL. Then heat it to boiling point. If sample
turns yellow, you let the cell run another day. After a couple of days the Ozone smell is really strong and the HCl test does not turn yellow anymore
-> Then you have an almost pure solution of NaClO4 :-).
As a side note, I believe the conversion from Chlorate to Perchlorate took about 3x the calculated run time.
Btw. I did not use any cell additives for any of the steps at this time (Later on, I used CaCl2 addition to form a diaphragm on the cathode when I
made Chlorates). I saw the addition of persulfates being mentioned a couple times, but I will admit, that I do not understand how these work in a
Chlorate cell - maybe someone can give me a hint.
Hope that helps & friendly greetings!
[Edited on 13-12-2025 by Mister Double U]
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Alkoholvergiftung
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Manyinterests. You can desolve your Sodiumperchlorate in Aceton. Sodiumchlorate is insoluble. So you can purify and see how much Perchlorate you have.
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ManyInterests
International Hazard
Posts: 1037
Registered: 19-5-2019
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Thank you guys,
| Quote: | Hello ManyInterests,
When I made Sodium Perchlorate many years ago, I was using roughly this route (has been 10+ years, so cut me some slack here):
Step 1: Electrolyze NaCl to make NaClO3.
I had a MMO anode capable of generating Oxygen - the ones which do not passivate.
I think I went to ~130% of the calculated run time and conversion was almost complete (explain in next step why I think that).
I also like to add the Faraday equation for calculating run time:
I * t = n * Z * F
I: Current [A]
t: Time [s]
n: Molar Amount [mol]
Z: Number of electrons needed for the reaction [e-]
F: Faraday Constant 96485[C/mol]
If you divide the equation by 'I' you get:
t = (n * Z * F) / I
Step 2: Boil down the cell liquor to a little bit more than saturation (I remember NaClO3 was very difficult to crystallize). Back then this was done
in a ceramic plated cooking pot. Boil the solution down to the point that a skin forms on the surface when blowing air on it and then maybe a little
bit more. If you stop too early, nothing crystallizes and if you get it right, a lot crystallizes. These 2 points are very close together (that was
very weird to me). Then place the solution in a freezer which goes to at least -10C. NaClO3 forms nice big cubic crystals. Some of them were measuring
~4mm on the edges.
Anyway, I do not think there was much NaCl left at the time, because none crystallized out at any time in the boiling down phase.
Lastly, I did the crystallization to purify the intermediate product. I was using self-made PbO2 electrodes at the time and I remember them being
quite sensitive to Cl[-] and [OH-].
Step 3: I ran the ClO3[-] to ClO4[-] conversion. PbO2 anode performed well without any brown stuff in the liquor - just some bigger pieces broken off
and at the bottom of the cell.
When conversion comes close to the end you will start to smell Ozone.
After that you let it run a day longer and take a small sample of the cell liquor and mix it with conc. HCL. Then heat it to boiling point. If sample
turns yellow, you let the cell run another day. After a couple of days the Ozone smell is really strong and the HCl test does not turn yellow anymore
-> Then you have an almost pure solution of NaClO4 :-).
As a side note, I believe the conversion from Chlorate to Perchlorate took about 3x the calculated run time.
Btw. I did not use any cell additives for any of the steps at this time (Later on, I used CaCl2 addition to form a diaphragm on the cathode when I
made Chlorates). I saw the addition of persulfates being mentioned a couple times, but I will admit, that I do not understand how these work in a
Chlorate cell - maybe someone can give me a hint.
Hope that helps & friendly greetings! |
Thank you for that information. Yes you seem to have done better than me with it, and maybe I will try again next time using my own home made PbO2
anode (I did make one from an old MMO anode I don't want anymore, I used lead nitrate as coating. I saw a video on doing it and followed it). But at
this point I am more interested in purifying what I have from any chlorate.
| Quote: | | Manyinterests. You can desolve your Sodiumperchlorate in Aceton. Sodiumchlorate is insoluble. So you can purify and see how much Perchlorate you
have. |
That does work, but it still needs HCl purification. There must be no chlorate in it in order to safely make ammonium perchlorate.
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