Sciencemadness Discussion Board - Perchlorate manufacture (not) with Graphite

Perchlorate manufacture (not) with Graphite

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dann2 - 4-6-2007 at 18:10

Hello,

I cranked up a Perchlorate cell some time ago using a Graphite anode. I put the results up here
http://www.geocities.com/CapeCanaveral/Campus/5361/basechem....
It is in the Graphite anode section.

The long and the short of it is this:
Cell was run for twice the 'run time'.
Current density on anode was 30 to 40mA per cm squared.

Anode wore at a rate of approx. 0.19 grams per Ah run through it.
Bugger all Perchlorate formed.
The electrolyte contained about 2% weight Chloride at the start. THis is the best I was willing to achieve by recrystallizing Home producted Chlorate.
No Perchlorate for 55 hours.
When cell was 'finished' I was unable to extract any usable Perchlorate by adding KCl. Only Chlorate or perhaps Chlorate containing small amounts of Perchlorate precipitated.

I do not believe that increasing/decreasing current density on Anode, using a different cell temperature, electrode arragement, additives etc etc will transform the operation of the cell.

Making Perchlorate with a Graphite anode is a HOPELESS
operation IMHO.

OH, did I mention the black mess

Dann2

Rosco Bodine - 4-6-2007 at 21:53

Isn't that a way lower current density than Mad Hatter was using ? I'd have to go back and check and find it , but it seems like he was using maybe five times that current density or more . Maybe there is a sweet spot
for the current density and you didn't find it .

IIRC , for each anode or cathode reaction there is an
optimum current density . How badly the efficiency drops off when you get away from that figure I'm not sure .....
but from your experiment it looks like it could drop the efficiency a good bit

dann2 - 5-6-2007 at 15:40

Quote:

Originally posted by Rosco Bodine
Isn't that a way lower current density than Mad Hatter was using ? I'd have to go back and check and find it , but it seems like he was using maybe five times that current density or more . Maybe there is a sweet spot
for the current density and you didn't find it .

IIRC , for each anode or cathode reaction there is an
optimum current density . How badly the efficiency drops off when you get away from that figure I'm not sure .....
but from your experiment it looks like it could drop the efficiency a good bit

Hello,
There is no sweet spot IMHO.

The current density that MadHater was using was 200mA per square cm. (Up and kicking with Lead Dioxide)
The graphite would get eaten as quick as you could carry goughing rods (what maDhatter use) to the cell.

Cheers,
Dann2

Rosco Bodine - 5-6-2007 at 16:16

So.... if we don't really want any perchlorate to form , then
we should use 30-40 ma per square cm . But on the other hand if we want the perchlorate cell to actually
make any perchlorate then we should use 200 ma per square cm ?

It would seem that getting some perchlorate along with
eaten anodes would be sweeter than getting no perchlorate along with eaten anodes .

Maybe at 30-40 ma current density , all you have is a bath warmer / anode eroder , and not a perchlorate cell at all .

If MadHatter was getting a good yield at 200 ma current density , then why do you pass judgement before you try
that same current density to see if your results track with his ?

I would bet good money that current density does matter and there most definitely is a sweet spot for each particular anode material , a niche value that is ideal .

hashashan - 5-6-2007 at 22:13

You should also try to make this with normal graphite and not gauging rods.

hashashan - 5-6-2007 at 22:14

Quote:

Originally posted by hashashan
You should also try to make this with normal graphite and not gauging rods.

sorry didnt notice you did use normal graphite,

Electrolysis Procedure

MadHatter - 5-6-2007 at 22:31

This is the electrolysis section of the method I found years ago for making KClO4
using gouging rods. Yes, I eroded a couple of rods because I prefer a higher current
density but I got the KClO4 I wanted. Before I bought a variable power supply, I
used a 6 volt/15 amp battery charger that worked very well. The linseed oil soaking of
gouging rods and keeping cell temperature below 40 C slowed the rate of erosion.

What really caught my attention about the procedure was that the chlorine produced at the
gouging rod bubbles up directly to mix with the potassium hydroxide produced at the
cathode. One improvement I made on the cathode was to spray paint the upper side so
that potassium hydroxide is formed on the bottom side only. The corrosive nature of the
cell will eventually remove the paint but for the most part keeps the electrode products
in very close contact.

BTW, I electrolyse KCl directly bypassing the NaCl route. I don't want sodium cations
contaminating the final product. After electrolysis, add water and boil until the K salts
are dissolved. Filter hot through several layers of white paper towels. This traps
the carbon, paint, and any other insoluble materials.

I use this method because it works for me and gouging rods are cheap.

Electrolysis
Using a coffee can for a source of steel, cut it out to form an inverted U shaped trough. Insert it in the mixture of salt and KCl dissolved in water. The (-) connector is connected to the steel. The steel U trough (similar to a rain gutter, except upside down) is setting at an angle to increase the amount of surface area in contact with the liquid. The carbon rod has some aluminum foil wrapped around the end of the rod, and the (+) connector is connected to it. The rod is positioned within the U shaped trough - under it, without touching. The charger is turned on, and he position & depth of the rod is adjusted to get 8 to 12 amps of current.
NOTE: A setup with the electrodes running electricity through an electrolyte is called a "Cell". This setup is commonly refered to as a cell throughout this description.

Let the liquid electrolyze for about 5 days continuously. Add water to make up for water lost during the process, and try to keep it roughly constant.

A couple times a day, you will need to check the current level, and adjust the rod position to keep the current in the 8-12amp range. Mine has been running between 40 - 50C, but commercial proceedures keep the temp just below 40C to reduce carbon rod errosion. The rods will gradually errode away, but if you use a 6V charger, one rod will probably last for the full 5 days.

You can also use higher voltage chargers, but you will probably need to connect several electrolytic cells together to keep the voltage accross ONE cell to be about 6 volts. If you use a 12 V charger, you will need 2 cells ( 12V/(6V per cell) = 2cells). If you connect more than 1 cell in series, you may need to use a voltmeter to check the actual voltage accross each cell - because it will change depending upon the resistance differences between the cells, which can be adjusted by re-positioning the rods.

The purpose for the U shaped trough cathode (-) electrode, is to cause the gas bubbles formed to generate a convection flow up through the trough. This causes the chemical products produced at each electrode to mix and react efficiently. Other electrode geometries will work, some better, and others worse. The key is to cause the two electrodes to be very close to each other, and cause the chemical products to mix well to help form chlorate and perchlorates. The WORST case situation is where the electrodes are on opposite sides of the cell, causing the chlorine gas produced at the anode (+) to tend to bubble and escape out of solution into the air.

hashashan - 5-6-2007 at 23:23

How did you make perch from K-chlorate??? its really poorly soulable only 7gr/100ml, what was the temperature of the cell?
How well did you clean off the chloride and how?

dann2 - 6-6-2007 at 17:08

Hello MadHatter and folks,

Glad you came in.

I don't want to annoy/insult/sound-like-a-complete-prick but here goes.... Drumm rollllll.

The procedure that you have read on the Internet for how to make Chlorate + Perchlorate (or Perchlorate) is:

*COMPLETE AND TOTAL CRAP*

The site that (I believe) you are quoting from is an old site
put up by a guy studying electrochemistry back in the ninties.
The guy has since gone on to graduate etc etc but the information regarding Perchlorate making on his page is NOT correct.
He himself had lost access to the page (left university) and could not correct it. The method he used to identify the 'Perchlorate' was the fact that he was getting lovely glinting crystals of Potassium 'Perchlorate'.
At run times before the glinting 'Perchlorate' appeared the observed crystallization was not of a pretty glinting variety. Thats because the early crystallizations were a mixture of KCl + some K Chlorate. He thought this was Chlorate----> then on to Glinting 'Perchlorate' later.
The lovely glinting crystals are pure Potassium Chlorate.
You will not get any Perchlorate worth talking about from this method. You cannot make Perchlorate in any sensible manner using a Graphite anode, PERIOD.

It has the added danger that people think/insist they have Perchlorate + combustable when in fact they have a mixtrure of Chlorate + combustable when they go to use it.
(Though K Chlorate is not a dangerous as Sodium Chlorate, it is not wise using a Chlorate when you think you have a Perchlorate).

There is a last remnant of the page you quote from here:

[Go to the second link down the page just below the yellow bar] Note the bold writing at the top.

http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

The run time table was taken from the page you quote. It was the first page ever on the internet explaining Chlorate making (Gouging rods and Graphite, some mention Pt). It was early days back then. Wouter Visser was in the same group so I am not trying to say they were clueless. The info for Perchlorate was simply wrong.

The link at the very bottom of the page below was put there in an attempt to stop people assuming they have Perchlorate (whether or not they are using Lead Dioxide, Platinum (or God forbid) carbon) when the cell is in fact still a 100% Chlorate cell. NO PERCHLORATE.

http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

As Hashashan pointed out (as well), it is not feasible to manufacture Potassium Perchlorate from Potassium Chlorate as the solubility of K Chlorate is too low for to obtain a sensible concentration of it in the cell.

If you have any of the 'Perchlorate' left, mix it with some sugar (50/50) and put a drop of concentrated sulphuric acid on it. It WILL ignite.
Mind you fingers (and more!) if using Sulphur etc.

Dann2

Graphite and Carbon Anodes

Rosco Bodine - 6-6-2007 at 23:17

Some reading through old patents tells me that indeed
carbon and graphite anodes of some type have most
definitely been used successfully for perchlorate production
in specially designed cells . And there are references griping about the difficulty , and the erosion , and having to interrupt production to clean out the graphite sludge from
*perchlorate* cells . And there are a few references which
mention use of "activated" graphite in such cells , but exactly what is "activated" graphite is unspecified .

I found one single patent that illustrates the use of a graphite anode in a perchlorate cell , and it is a divided cell .

And I found one patent which seems to describe what might be the idea of an "activated" graphite , but I am not certain this is the same thing .

Attachment: US1279593 Perchlorates Using Carbon Anode.pdf (173kB)
This file has been downloaded 875 times

"Activated" ???? Graphite

Rosco Bodine - 6-6-2007 at 23:22

Maybe something similar to this is what is meant by
activated graphite . Evidently graphite can be glazed
with a conductive doped alumina baked on at a moderate
temperature to improve its durability .

Attachment: US3377265 PbO2 doped alumina anode coating.pdf (326kB)
This file has been downloaded 866 times

dann2 - 7-6-2007 at 16:36

Quote:

Originally posted by Rosco Bodine
Some reading through old patents tells me that indeed
carbon and graphite anodes of some type have most
definitely been used successfully for perchlorate production
in specially designed cells . And there are references griping about the difficulty , and the erosion , and having to interrupt production to clean out the graphite sludge from
*perchlorate* cells . And there are a few references which
mention use of "activated" graphite in such cells , but exactly what is "activated" graphite is unspecified .

I found one single patent that illustrates the use of a graphite anode in a perchlorate cell , and it is a divided cell .

And I found one patent which seems to describe what might be the idea of an "activated" graphite , but I am not certain this is the same thing .

Hello Rosco,

I'll be dammed!
Perhaps there is hope and redemption for humble down trodden Graphite in the production of Perchlorate after all. :cool:

Will read patent.

Another angle for getting Graphite to product Perchlorte may be to start with Lithium Chloride (or Chlorate). According to a source I read, Lithium Chloride converts very easily from the Chlorate onto the Perchlorate (Using Pt or Lead Dioxide).
Perhaps it will convert fairly easily using Graphite anode.....perhaps not.
The reason given for Lithium Chloride converting easily into Chlorate------->Perchlorate was because of the small atomic radi of the Lithium ion.
This explanation does not make sense to me because the Lithium ion (or Na or K) is only a spectator ion in the Chlorate/Perchlorate making process AFAIK.

Lithium does not introduce a yellow interfering colour into pyro mixtures if you go on to make K. Chlorate or K. Perchlorate.

BTW I have been running the Graphite anode cell at a higher current density just to make sure the old horse in well and truly dead.
I do not believe it will make a jot of difference to Perchlorate yield ie. still effectively zero for all intents and purposes.

Dann2

Rosco Bodine - 7-6-2007 at 16:57

Yeah I am a bit doubtful about the graphite anode myself , and it seems like I recall some additive , perhaps dichromate was absolutely required to prevent a competing reaction on the cathode where perchlorate was reduced right back to chlorate as it formed ....possibly why the requirement for a divided cell described in the patent .

Anyway I have been looking at other anode materials and mostly only considering graphite for substrates or for cathodes . I'm so cheap I don't even like the idea of
corroding graphite , aside from the messy sludge it makes .

garage chemist - 7-6-2007 at 17:26

Why try so hard making perchlorate electrolytically, if its so hard to find a good anode for this just make chlorate with graphite or MMO and thermally decompose it.
If I had time I could document and post the procedure of how I made KClO4 from NaClO3. Is there even interest in this oldest and first ever used method of obtaining perchlorates?

12AX7 - 7-6-2007 at 17:57

It's been explored in another thread. As I recall, it's a load of crap, i.e. not very successful at all. Takes precise temperature, pure reagents (including the crucible, which must be tolerant of a strong oxidizer and molten salt) and long times to give low yields.

Tim

jpsmith123 - 7-6-2007 at 18:11

Garage Chemist are you still toying with the idea of trying to make a PdO based MMO anode?

I think that is one unexplored area that could potentially be very useful.

garage chemist - 7-6-2007 at 18:33

Yes, MMO anode is one of my projects, I have bought two strips of grade 1 titanium sheet from ebay which are yet to arrive.
PdO will be my first experiment, and then RuO2/TiO2 coating as in Beer's patents. TiCl4 will soon be ordered, as will Ru powder. Also, synthesis instructions for titanium tetrabutylate must be acquired.

Thermal decomposition of chlorate is NOT a load of crap, I had very good success with it, and the crucible can simply be a small beaker since glass is suitable as the container.
The correct temperature can be judged by the gas evolution, a thermometer is not necessary.
The chlorate only has to be free from heavy metals, while chloride impurity is no problem since the reaction produces chloride as side product anyway.
50% yield is easy to obtain in 2 hours reaction time.

jpsmith123 - 7-6-2007 at 18:49

I'm surprised that you're so strongly against the idea of a PdO/TiO2 mixture. Is this simply because there are no specific examples of this mixture in the patents, or is there a theoretical reason you're opposed?

12AX7 - 7-6-2007 at 18:50

Really, I recalled differently from that thread.

Ah well!

garage chemist - 7-6-2007 at 19:02

Did I say I was against a PdO/TiO2 mixture? The reason that I am not considering it is that i have found no patents that use it.
Also, RuO2 and TiO2 have similar crystal structures which enables them to form mixed crystals (read it on a link on dann2's site) which is the reason that RuO2/TiO2 coating is more resistant than any other MMO coating.
I suspect that PdO and TiO2 will not be able to form mixed crystals, which would make PdO/TiO2 even less resistant than pure PdO.
Whenever PdO was used as MMO coating in mixture with something else, it was with Tantalum oxide. Those probably form mixed crystals.

jpsmith123 - 7-6-2007 at 19:43

Well you clearly implied you were against it. And I was trying to understand your reasoning. If you have all the materials necessary to test it, and you say you don't intend to test it, I figured there must be a strong reason why. Especially since it seems that the PGM oxides *by themselves* are not very robust.

The Japanese patents I cited before state or imply that PdO doesn't work very well by itself...it doesn't stick well to Ti. And Beer's patent 3632498 says basically the same thing (about all the PGM oxides including PdO). Then on page 4 it says:

"The problem of rendering the oxides of the noble metals and other metals in finally divided condition adhesive and at the same time resistant is now solved by virtue of the co-precipitation of the non-film-forming conductors with the oxides of the film-forming metals. It is surprising for example that palladium oxide, platinum oxide and ruthenium oxide are then fully resistant." (Note Beer specifically mentions PdO as being "fully resistant" when co-precipitated with a film-forming oxide).

Then on the same page of the patent the table shows Pd/Ti co-precipitated oxides as being qualitatively the same as the other MMO compounds.

And finally there is an example in the patent of a PdO based MMO, and that is example VII (it is not TiO2 but TaO2).

So as I see it, if you just try to put PdO on by itself, you will likely be wasting your Pd, whereas if it goes on with TiO2, you will likely end up with a useable anode that may make ClO4 and ClO3.

And I don't want to see you waste your Pd and leave the ClO4 question unanswered.

[Edited on by jpsmith123]

garage chemist - 7-6-2007 at 19:54

Alright, you proved my theory wrong, I admit.
I havent read the patent you cited until now (or atleast not thoroughly enough).
I have only started reading up on the whole MMO thing very recently, and surely still have something to learn.
A Pd based MMO anode which is as resistant as a Ru based one would be optimal- Pd is both cheaper and easier to get and work with than Ru.

When my titanium arrives and I start experimenting with MMO coatings I will open a thread exclusively on homebrew MMO anodes. I hope this to be more successful than the PbO2 anodes, which nobody has gotten to work satisfactorily AFAIK.

[Edited on 8-6-2007 by garage chemist]

jpsmith123 - 7-6-2007 at 20:05

"A Pd based MMO anode which is as resistant as a Ru based one would be optimal- Pd is both cheaper and easier to get and work with than Ru."

Exactly! And according to the narrative in one of the Japanese patents, it may have much better catalytic properties than Ru. If this is true, I would expect higher efficiency in a ClO3 cell, and the possibility to make ClO4.

I've got everything I need to try it also. I just have to get out of this tiny little apartment I'm in and get my workplace set up again. I got some 0.032" CP titanium sheet from ebay a while ago which I cut into 2" x 8" strips all set to go.

garage chemist - 7-6-2007 at 20:58

Ah, time is my problem, I'm stuck in this small apartment during the week at the town where I'm studying, and can only drive home (2 hours) to my lab every weekend. This is really limiting any experiments I can do.

Could you write down your japanese patent numbers again? That would be nice. I havent seen them in the other thread.

My titanium sheet is 3mm thick, which probably is excessive, but I have seen current densities of up to 8000 Ampere/m^2 be used in some of the patents, which is 800 mA /cm^2 if I calculated correctly. This is an extremely high current density. I didnt even use such high current densities with my Pt wire anode in my perchlorate cell.

My objective is to make an MMO anode which only produces chlorate, though. I can clearly see why industry keeps chlorate and perchlorate production strictly apart- it simply is way more economic to keep the stress of the initial chlorate production away from your precious ClO4- capable anode.

MMO anodes will OWN the disgustingly messy PbO2 bullshit!!!

Higher current density

dann2 - 8-6-2007 at 17:41

Hello,

For all (if any) doubters I ran a quarter liter of the cell solution

(extracted from above the black sludge) for a further 264 Ampher Hours at

a current density of between 120 and 220 mA per square cm.

(Graphite anode of course.)

Density varied as

the anode wore.

The liquid (at the top of the black sludge) after settling was still a

very black colour, blacker than the first run. The sludge made up most of

the cell contents.
I added a small quantity of dilute KCl solution and got a ppt. This time

the ppt looked more like Perchlorate as the crystals did not glint.
I washed the ppt four times.
Dried and mixed (50/50) with sugar.
A drop of Sulphuric caused instant ignition.
I have either Chlorate with Perchlorate contamination or Perchlorate

with Chlorate contamination or whatever you like to call it.
It should be noted that a total of approx. 500 Amper Hours per mole

Chlorate has passed through this solution.
(A total of approx. 60 Ampher Hours would be the amount needed to convert

one mole Chlorate into Perchlorate at 100% current efficiency.)
No usable Perchlorate can be extracted using KCl as the 'extractor'.

BTW the concentrated sulphuric acid test is a quick and easy test for the

presence of Chlorate with combustable.
I tried it with pure K Perchlorate + sugar (50/50) and got no ignition.

Fineto Fin Finish End of Perchlorate with Graphite thread.

Alembic (posted here) has made a successful Ti substrate anode. He too has made successful GSLD Anode way way back in antiquity

.

The Lead Dioxide is two things.
1) The poor man's Platinum
2) The lazy man's Platinum
Cheap (if you can get it to work) and lazy as you plonk it in a Chloride solution and come back and extract nearly pure Perchlorate.

What makes you guys think that MMO will make Perchlorate?
Have you seen it anywhere?
The Platinum based pool chlorinator anode (posted on this site by Joe) was said to be Platinum based by a guy who seems to work with such anodes. When he said that it was Pt based he meant Pt metal, not oxides of Pt. It was black Platinum which is a form of Pt metal that deposites under certain plating conditions. (Perhaps it containes some Pt Oxide but it is (surly) the Pt metal that is/was making the Perchlorate.

Regarding the thermal decomposition route there is a patent (on my site?? I think) that explaines the process in detail.
As far as I can recall you need to keep the temp. between 400 and 420C for a fairly long period of time (approx. 24 hours) Easy enough if you have a temp. controlled device I guess.

As far as the Perchlorate with Graphite thing is concerned it was just something that I wanted to put to rest one way or the other for once and for all. The description of u shaped cathodes with Graphite anode is still sitting out there in usenet. It sounds very simple and convincing.

Dann2

jpsmith123 - 8-6-2007 at 19:23

Hello Dann2,

I speculated that certain types of MMO anodes may make perchlorate. (I don't know exactly which types, but taking everything I've read at face value, I would say PtO2 and PdO based MMO coatings stand a good chance).

This is based on Beer's patent# 3711385 (attached; see examples 8 and 11, and read the first few pages of text), and also on statements from at least two people who claim to have made it using a pool chlorinator anode.

IIRC, in the body of the patent, Beer claims that the PGM oxides have catalytic properties similar to, if not generally better than, the metals themselves.

The implication is that if Pt makes perchlorate, then so too will a thin film of PtO2; and it will supposedly last much longer. Having the other oxides present, e.g., TiO2, makes the coating more robust, but also changes the catalytic properties, according to what I read.

And that's all I can say about it at this point.

What bothers me is: Why is nobody selling a commercial MMO based perchlorate anode? And why only PbO2 and Platinum? Why not MnO2 and SnO2 based anodes for that matter? For all the various patents out there, only Pt and PbO2 are commercially viable for some reason?

Attachment: 3711385.pdf (1.1MB)
This file has been downloaded 969 times

dann2 - 9-6-2007 at 15:08

Hello,

MnO2 anodes were used years ago (can't remember where I read this) and were called Duriron. Perhaps a search of the Patents for Duriron would pull up some info.

Since they seem to have faded away perhaps they were not so good at doing their job.

Dann2

alancj - 16-6-2007 at 17:42

Quote:

Originally posted by jpsmith123
What bothers me is: Why is nobody selling a commercial MMO based perchlorate anode? And why only PbO2 and Platinum? Why not MnO2 and SnO2 based anodes for that matter? For all the various patents out there, only Pt and PbO2 are commercially viable for some reason?

I'm guessing that the amount of capital required and just trying to get companies to switch to an unproven anode may play a big part in the limited commercial success of a new type of anode. Even if other types technically work the marketing guys might not be able to persuade the penny pinchers.

-Alan

Rosco Bodine - 16-6-2007 at 18:37

Quote:

Originally posted by dann2
Hello,

MnO2 anodes were used years ago (can't remember where I read this) and were called Duriron. Perhaps a search of the Patents for Duriron would pull up some info.

Since they seem to have faded away perhaps they were not so good at doing their job.

Dann2

Something doesn't make sense there .....maybe the duriron was used as a substrate ?

Duriron is the trade name for a durable iron corrosion resistant high silicon content ~15% iron alloy used for
plumbing tanks and valves in the chemical industry .

It was invented in 1912 and the Duriron company of Dayton Ohio became a public corporation 1942 , growing into a
large conglomerate known today as flowserve
http://www.flowserve.com/eim/index.html

Gouging Rods

MadHatter - 17-6-2007 at 07:16

Dann2, I performed the tests on my gouging rod perchlorates using the
sulphuric acid on sugar/KClO4 tests and with methylene blue. Both tests confirm
that I have KClO4. All the sulphuric acid did was char some of the sugar and the
methylene blue turned a very pretty violet colour. The KClO4 works GREAT in flash mixes.

I will acknowledge that the efficiency with additives such as potassium dichromate,
potassium persulphate, or sodium fluoride helps but I'm tired of eating up gouging
rods and the efficiency is still horribly low. Since perchlorates will be harder to obtain
because of the wankers at the CPSC, it's time to move on finding a more durable
anode. PbO2 on a graphite substrate works but the coating, even thick, is fragile.

I'm running out of KClO4 so I need that anode soon, especially with the July 4th
holiday around the corner.

BTW, I've visited and must say you have a great website !

dann2 - 18-6-2007 at 17:43

Hello Madhatter,

I went back to the original 'Perchlorate from Graphite post'(not the actural name of post) and snipped out the full process description.
The url is:

http://www.sciencemadness.org/talk/viewthread.php?tid=5050&a...

Most of snips come from page 2
_________________________________________

..............
JP, the treatment for gouging rods involves peeling off the copper plating and then soaking
in linseed oil. This slows the erosion in the cell. I made 8 LBS of KClO4 using gouging rods.
It's a matter of technique. Keep the cell temperature below 40 C and the erosion proceeds
at a much slower rate. Use a cut up steel can for the cathode and don't worry about
the iron hydroxide that forms because the fluffy white shit is so insoluble that it, along with the
carbon bits filter out readily. I bend the steel to make an inverted V shape and the gouging
rod sits directly below it. This way, the rising chlorine runs into the hydroxide formed at the
cathode. My cell has a 5 litre volume.

Few posts later:

My cell body is basically a 5 litre glass cookie jar that I found at Walmart. I like the V-shape
cathode because the chlorine or oxygen rises from the anode to mix with cathode
products. This is why I don't need to stir. The worst possible configuration for the
electrodes is to have them sitting on opposite sides of the cell. Very little mixing occurs.
As mentioned before, keeping the cell temperature below 40C(104F) keeps the rate of
erosion down.

Solubilities for compounds from CRC 62nd Edition(1981-1982), grams per 100ml H2O:

KClO4 .75 @ 0C 21.8 @ 100C
NaClO4.H2O 209.0 @ 15C 284.0 @ 50C

I start my electolyte at 9% by weight KCl. A little NaCl is mixed in because oxidation
of NaCl is more efficient than KCl. The metathesis reaction with KCl forces KClO4 out of
solution because of its much lower solubility. I put 2g of NaF in the electolyte to improve
current efficiency. Voltage is at 6 and amps are adjusted to keep the cell temperature
below 40C. After completion, FeSO4 is used to destroy any residual chlorate. The rest is
fractional crystallization to get the KClO4.

Few posts later:

Perchlorate production begins when the chloride(by weight) drops below 10%. This is why I
start my electrolyte at 9% to get things going immediately. I have to replace the gouging rods
a few times during the process but that's fine with me because they're cheap to use.
8 LBS of KClO4 for about 3.12 USD(6 rods) is bargain IMHO. I still have almost 90 rods left.
A few were consumed early on while tweaking the technique and of course producing
straight chlorate using saturated KCl solutions. The lovely cactus needle like formations
are indications that the chlorate is being produced.

Dichromates, fluorides, and persulphates are used to increase the efficiency of the operation.
I've used all 3 at different times. Personally, I like NaF. It works very well and it's cheap.
As for cathodic protection, I couldn't give a damn. I'm not worried about consuming a
soup can.

Few posts down:

I like to have .2 amps per square centimeter on the anode. That's about 7 amps on a 3/8"
by 12" gouging rod. I keep the voltage at 6.

_________________________________

END OF PROCESS CLIPS

The reading of the process is not clear to me how or what you started with.
I don't know if some of the inconsistencies are typos.

You say
" A little NaCl is mixed in because oxidation
of NaCl is more efficient than KCl."

But we are making Perchlorate, do you mean a little NaCl03?

You say:
"I like to have .2 amps per square centimeter on the anode. That's about 7 amps on a 3/8"
by 12" gouging rod."

Surface area of 11 inch(active length) by 3/8 inch rod = 83.6cm squared. At 7 amps that's 0.083 amps per square cm on the anode.
Which is the correct (approx.) figure?

To dissolve 3180 grams K. Chlorate (enough to make 3600 grams Perc.) at 35C takes about 25 liters. Is this approx. what you used or did you keep adding Chlorate into the one 5 liter cell (one big run)?

To dissolve 3600 grams (8 lbs) KClO4 (K. Perchlorate) it takes about 18 liters of water at 95C. Is this approx. what you used in total when recrystallizing?
You will need far more IMHO to stop K. Perc. from crystallizing out on the filter to get rid of the black shit.

I would like to ask the following:

What was the starting concentration of 'stuff'(list all salts + approx. concentrations) in the cell?
Did you use the same 5 liters of water/electrolyte solution through out the manufacture of the 8 lbs of K. Perchlorate?
How long (approx.) did it take to make the 8 lbs of K. Perchlorate?
How many amps into cell?
What was the current density on the Gouging rod anode?
Did you use one Gouging rod at a time?

I tried making Perchlorate (Sodium Chlorate + about 2% Sodium Chloride + NaF) using Graphite and got no sensible amounts of Perchlorate forming after a huge run time.
Is the difference all to do with using K. instead of Na..........I have me doughts but then again it is something I have not done using (more dilute compared with Na) mostly K salts.

Sorry about all the questions. More will probably follow!!!!!!!!!!!

If Perchlorate can be made at a rate of 6/8 = 0.75 (3/8" by 12")rods per lb Perchlorate I will eat my (and yours too) hat.

Quote:

I'm running out of KClO4 so I need that anode soon, especially with the July 4th
holiday around the corner.

BTW, I've visited and must say you have a great website !

Thanks.
If I can get this to work I will put it on the front page! Most of the material comes from others hard work.
Fourth comming up?? Time to get out the Gouging rods.

Cheers,
Dann2

dann2 - 18-6-2007 at 18:21

Quote:

Originally posted by Rosco Bodine

Something doesn't make sense there .....maybe the duriron was used as a substrate ?

Duriron is the trade name for a durable iron corrosion resistant high silicon content ~15% iron alloy used for
plumbing tanks and valves in the chemical industry .

It was invented in 1912 and the Duriron company of Dayton Ohio became a public corporation 1942 , growing into a
large conglomerate known today as flowserve
http://www.flowserve.com/eim/index.html

Hello Rosco,

The place where I saw Manganese Dioxide anodes being called Duriron was in the following artical:

JOURNAL OF APPLIED ELECTROCHEMISTRY 8 (1978) 327-332

The preparation and behaviour of magnetite anodes

M. HAYES*, A. T. KUHN

Department of Chemistry and Applied Chemistry, University of Salford, Salford, Lanes., UK

......, as do the 'duriron'
or MnO2-coated electrodes......

It is available on this web site.
Perhaps I have taken it out of context.

Good luck with your other endeavors.

Dann2

Rosco Bodine - 18-6-2007 at 22:37

Yeah I think you have it out of context . Because duriron is a trademark brand name nearly a hundred years old for the corrosion resistant silicon-iron alloy , which has been used alone for anodes or substrates . Maybe it was used as the center core in those cast magnetite anodes
or maybe even by itself in some applications .

Thanks , I got a couple of weeks work to catch up
at another location so I may be going offline for a
few days at a time .

12AX7 - 19-6-2007 at 16:31

Hmm. Applying this to my cell, I find around 6V, 100A is required (about a horsepower!), and I'll be able to produce roughly um...

Well, one 3/8" x 12" rod is 7 in^3, and if it averages 0.75 of them to make a pound, then it goes at a rate of 5.3 in^3 graphite/lb KClO4 produced (note this includes the unusable stub left over at the top). (You can figure the typical density of industrial graphite into this to get wt/wt.)

I have two 40 in^3 graphite bars, therefore I could produce 15.2 pounds of potassium perchlorate.

But no estimate of time, current efficiency, temperature control (that size cell WILL need cooling with half a kilowatt of heat inside it) or voltage/current control (you mention 6V, but you also say current was controlled -- how, exactly, was it controlled while voltage remains fixed? (Length of rod in solution?) Or did you just forget your electronics when you said that?), etc.

Incidentially, the two bars cost me about $20. If the cell runs for one week, producing 15 pounds of perchlorate, it consumes 117.6 kWh (assuming a conservative 700W consumption figure; yeah, I would use schottky rectifiers for the power supply), costing $12 of electricity and $20 in graphite. Plus a few hours of my time, though counting that is tricky (as I'm not on payroll when I'm at home, and if I were doing this industrially, I would have much larger cells -- and, ironic to this thread, no graphite muck -- providing economy of scale). So I'd get around $2/lb KClO4. Seems kind of expensive, at least compared to a licensed drum of it...

Tim

A manganese analogue of duriron

Rosco Bodine - 20-6-2007 at 10:01

There is a manganese loaded cobalt - silicon alloy which was developed as an improvement for duriron when used for the
anode in copper refining . See attached patent . I do not know if the alloy is presently manufactured or what would be its trade name . Likewise I think there also is a high manganese content variety of duriron itself .

It would seem to be a very likely candidate substrate for a baked on beta MnO2 material dervied from Mn(NO3)2 ,
which could probably then be coated with PbO2 .

I have seen a few other references to high manganese or high chromium content varieties of stainless steel alloys which have been baked and treated with manganese and/or chromium salts , and other salts also , in schemes which are analogous to those used for titanium substrate anodes .

BTW ordinary 316 stainless has been mentioned in a few patents as something of a possible substitute for titanium which has performance in service almost as long as a titanium substrate anode , the main difference being that after a year or so of operation when the protective oxides layer fails and the substrate alloy is exposed , that the stainless substrate disintegrates .....while the the titanium substrate just flakes off its coatings and then usually remains for the most part in one piece , except for pitting in the places where the coatings have failed . So while operating normally with intact protective coatings , evidently
a few alloy or alternative substrates to titanium are possible , but the titanium substrates fail more gradually and slowly when the protective coatings eventually crack or are are otherwise permeated by the electrolyte . Evidently none of these anode combinations are absolutely permanent
or perfect , it is simply a matter of some combinations being longer lasting than others and having different behaviors when they do fail sooner or later .

Attachment: US1437507 Cobalt Manganese Chromium Silicon Alloy for Anode.pdf (293kB)
This file has been downloaded 758 times

more concerning possible "activated" graphite

Rosco Bodine - 23-6-2007 at 23:37

Reportedly a *single* dip and bake treatment with certain oxides which are catalytic can also increase the erosion life of anodes by 10 times compared with an untreated anode , and this applies to graphite anodes . This treatment may even be more effective on the cheaper grade more porous grades of graphite .

I would suppose that multiple coats and an increased buildup of the thickness of the catalytic oxide would have an even greater effect .

Cobalt nitrate is specificially reported in this regard in the attached patent . Bismuth is also a known catalytic oxide ,
and manganese would probably work as well . This is a similar sort of process as would be used to apply the baked on intermediate oxide layer on a titanium substrate . And evidently it is significant benefit to a carbon anode also .
The carbons will still erode , as this superficial treatment
does not result in a permanent anode . But it may be a relatively simple way of slowing the erosion and improving the efficiency of the anode significantly .

[Edited on 24-6-2007 by Rosco Bodine]

Attachment: US6001225 Baked Cobalt Oxide coated_anodes.pdf (43kB)
This file has been downloaded 784 times

MnO2 impregnated/coated carbon gouging rods!

Xenoid - 24-6-2007 at 14:14

Quote:

Originally posted by Rosco Bodine
I would suppose that multiple coats and an increased buildup of the thickness of the catalytic oxide would have an even greater effect .

Cobalt nitrate is specificially reported in this regard in the attached patent . Bismuth is also a known catalytic oxide ,
and manganese would probably work as well . This is a similar sort of process as would be used to apply the baked on intermediate oxide layer on a titanium substrate . And evidently it is significant benefit to a carbon anode also .
The carbons will still erode , as this superficial treatment
does not result in a permanent anode . But it may be a relatively simple way of slowing the erosion and improving the efficiency of the anode significantly .

[Edited on 24-6-2007 by Rosco Bodine]

Hi

I am currently having a go at something like this - trying to impregnate and coat carbon gouging rods with MnO2 to extend their life particularly in a chlorate cell!

Thermal decomposition of Mn(NO3)2 to MnO2 seems to be a particularly suitable technique for the amateur to explore for a number of reasons.

1) Manganese precursor chemicals are readily available from hydroponics and pottery suppliers.
2) It doesn't involve the use of poisonous Pb chemicals.
3) There are no "complex" procedures involved ie. plating.
4) There is "heaps" of literature and patents available - this technique is used for the production of tantalum capacitors and others since the 60's and for various anodes.

Not currently having nitric acid I made Mn(NO3)2 solution via the double dissolution (metathesis) reaction of Ca(NO3)2 and MnSO4 causing the precipitation of CaSO4. The resulting white curdy gloop was so thick that more water needed to be added to make it pourable. This was then placed in my homemade pressure filter and a slightly pink clear solution was obtained. I am currently just using this solution as obtained, without any further purification, or adjustment of concentration as a "proof of concept"

My gouging rod treatment consists/wil consist of:

1) Stripping the copper in the usual electrochemical procedure (I always leave about 2 or 3cm of copper plate on the non-pointed end so a wire can be soldered on, or a stainless steel clip attached, to achieve good electrical contact.
2) Soaking the rods in 2 changes of distilled water overnight.
3) Drying in a oven at 150oC for several hours.
4) 10 (yes 10!) cycles consisting of;

a) vacuum impregnation for 30mins in the Mn(NO3)2 solution. (I just use an old rotary refridgeration compressor and PVC pipe with endcaps - the same as for the linseed oil impregnation, I have no idea of the vacuum achieved - its not much!).
b) warm air drying to remove surface moisture.
c) 15 mins heating at 100oC
d) 15 mins heating at 200oC (for the heating cycles I am currently using a hot air gun attached to an aluminium tube in which the rods sit. I have a cheap DVM with a thermocouple attached to measure the temperature)
e) cooling to room temperature

Note: Poisonous NO2 is emitted during the heating (thermal decomposition) cycle. The smell starts to become noticeable at about 140oC

After each thermal cycle the rods appear to be covered in small nodules of MnO2 where solution has erupted out of the numerous holes and cavities that these rods are renowned for. I merely wipe them with a tissue to smooth off the surface before proceeding to the next cycle.

So far I have completed 8 of the 10 cycles.

I can see the MnO2 coat building up on the surface, around the holes and cracks but there is still solution being ejected from various points so the pore space of the rods is not yet completely filled with MnO2. I would like the the pore space filled to stop "wicking" of the electrolyte.

5) I then intend to do 10 further cycles of just dipping and heating in an attempt to build up the suface layer of MnO2.
6) Followed by a final "burn" for about 30 mins at 250oC to complete the process.

I am currently only doing 2 rods for experimental purposes but it would be just as easy to do do a dozen rods at the same time!

I realise this all sounds quite complicated, but there is no "easy" route to a homemade anode! This procedure has LOTS of scope for amateur experimentalism! Including:

1) Purity of initial chemicals.
2) Concentration of solution.
3) Water/Ethanol solution - Mn(NO3)2 is apparently soluble in ethanol.
4) Duration, number, and temperature of impregnation/ decomposition cycles.
5) Introduction of "doping" elements as mentioned in previous posts.
6) Additional plating of MnO2 or others over the thermally decomposed MnO2
7) Thermal decomposition onto high quality graphite and valve metals in etched or sintered form (why are they called valve metals???).

I will report how I get on in several days time!

Xenoid

Added MnCO3 should help increase the loading

Rosco Bodine - 24-6-2007 at 15:28

The residue of sulfates could cause you troubles going from
the double decomposition using calcium nitrate . It would probably be cleaner to use sodium carbonate or bicarbonate
and filter out the carbonate , rinse it good with distilled water , then neutralize the residue with HNO3 , or possibly boil it with ammonium nitrate .

Added 10% content of MnCO3 to the Mn(NO3)2 will increase the viscosity and loading and quality of the baked film of
MnO2 . So you could save out some of the carbonate or
you could carefully weigh the carbonate and then add only enough HNO3 for 90% conversion . I suspect what this does is result in a solution containing either a basic nitrate of manganese or a soluble double salt , or both as a sort of sol complex which thickens the mixture . The mixture may not be stable on keeping so you may have to prepare it as needed .

Cobalt , Bismuth , and Antimony are reportedly dopants for MnO2 that are known to be catalytic for perchlorate production .

Just a guess , but others of interest might be be vanadium ,
chromium , cadmium , tin , iron , lead , phosphorous and boron .

I would bet money that graphite manufacturers probably have some sort of proprietary recipe of dopants which were added as deliberately included impurities to the carbon powder which was / is made into graphite destined for particular customers .....things which improved its performance in certain niche applications . Even the spectrum of light produced by arc lamps was probably modified by certain additives and also carbons used for anodes probably each had a special recipe .

So what is being done here is probably a rediscovery of
something that was being done already a hundred years ago . A lot of this technology was probably never published ,
and that is why it is impossible to find , it is locked away in some company's safe as a process secret . Or perhaps it is simply hidden in plain sight in some long list of unspecified use but specified formulations of various graphites for industry .

About the "valve metals" ....it goes back to " Fleming valves "
which were rectifier tubes , and the British reference to rectifiers which allow one direction current flow as " valves "
for their similarity to check valves like used in water lines or other hydraulics . When a valve metal is used as an anode
there is formed an oxidized layer of the metal which gradually
becomes more and more resistant to current flow as that layer grows in thickness . It usually has the property of a
diode .....so that if the polarity is reversed and the valve metal substrate is made the cathode , then current flows
much more easily , while on the other hand it essentially stops current flow in the direction that formed the oxide layer . The idea of dopants is to disrupt that polarizing effect towards electrical current flow , so that the metal which ordinarily would stop functioning as an anode continues to conduct electricity as easily as possible in the same direction as the current which would otherwise anodize
it , and then stop . The idea is to keep the corrosion resistance of the oxide layer mostly intact , but at the same time to allow easy flow of current through the oxide to the metal anode .

[Edited on 24-6-2007 by Rosco Bodine]

Attachment: US3553087 Improved beta MnO2 from Mn(NO3)2 plus MnCO3.pdf (159kB)
This file has been downloaded 754 times

Xenoid - 24-6-2007 at 17:07

Quote:

Originally posted by Rosco Bodine
The residue of sulfates could cause you troubles going from
the double decomposition using calcium nitrate . It would probably be cleaner to use sodium carbonate or bicarbonate
and filter out the carbonate , rinse it good with distilled water , then neutralize the residue with HNO3 , or possibly boil it with ammonium nitrate .

Added 10% content of MnCO3 to the Mn(NO3)2 will increase the viscosity and loading and quality of the baked film of
MnO2 . So you could save out some of the carbonate or
you could carefully weigh the carbonate and then add only enough HNO3 for 90% conversion . I suspect what this does is result in a solution containing either a basic nitrate of manganese or a soluble double salt , or both as a sort of sol complex which thickens the mixture . The mixture may not be stable on keeping so you may have to prepare it as needed .

[Edited on 24-6-2007 by Rosco Bodine]

Hi,
Yes, I was aware of the sulphate interference, it was mentioned in one of the papers I looked at. But, not having any nitric acid I thought I'd give it a go anyway, this is just a preliminary attempt at treating gouging rods. If this method shows any promise I'll try and crystallise out some pure Mn(NO3)2 - not sure how easy this will be with its high solubility - does anyone have a solubility curve for Mn(NO3)2?

Hmmm.. adding MnCO3, it has a solubility of .0065 ie. insoluble not sure how - it may be in the paper you quoted, I havn't read it yet!

As I pointed out previously, there is plenty to try out here - starting with the purity of the main ingredient

I have now completed 10 cycles, the rods look like they have been in a fire, and are covered in a nodular coating of MnO2.

Xenoid

dann2 - 24-6-2007 at 18:40

Hello Xenoid,

At the end of the day someone has to do it!

Quote:

Originally posted by Xenoid

4) There is "heaps" of literature and patents available

OH NO!!!!!!!!!

Quote:

Not currently having nitric acid I made Mn(NO3)2 solution via the double dissolution (metathesis) reaction of Ca(NO3)2 and MnSO4 causing the precipitation of CaSO4.

Xenoid

Surely you will get no Sulphate interference as it is easy to seperate the chemicals as one is insoluble?

Dann2

Rosco Bodine - 24-6-2007 at 19:30

Quote:

Originally posted by dann2

Quote:

Originally posted by Xenoid

4) There is "heaps" of literature and patents available

OH NO!!!!!!!!!

If you are digging potatoes and just happen to find a gold nugget ....you don't throw it away just because it isn't a potato !

Old Rosco is like a snapping turtle when he latches onto something , he doesn't let go till it thunders

Quote:

Not currently having nitric acid I made Mn(NO3)2 solution via the double dissolution (metathesis) reaction of Ca(NO3)2 and MnSO4 causing the precipitation of CaSO4.

Xenoid

Surely you will get no Sulphate interference as it is easy to seperate the chemicals as one is insoluble?

Dann2

It's a rough separation usually because the CaSO4 is not entirely insoluble and it takes some subsequent purification to get out the sulfate that sneaks over on the first pass . It probably won't matter much on something like this , but the sulfate impurity can be an issue in some reactions , so it's generally better to go a different way like the carbonate intermediate .

BTW , concerning bismuth oxide , here is a link for a possibly useful method for a nanoparticulate crystalline bismuth oxide which develops at 400C .

http://dx.doi.org/10.1016/j.ceramint.2004.06.013

[Edited on 25-6-2007 by Rosco Bodine]

MnO2 treatment of gouging rods - continued!

Xenoid - 25-6-2007 at 12:57

I have now done 4 cycles of surface treatment on the rods!

The cycle comprises;

1) Dipping the rod in the Mn(NO3)2 solution for about 5 seconds. I've added a few drops of Monsanto "Pulse" to the 100mls of dipping solution (Pulse is a penetrant/wetting agent for use with "Roundup" herbicide).
2) Warm air drying, to remove visible moisture.
3) Heating for 15 minutes at 200oC

I am starting to think that the vacuum impregnation cycles were not nescessary because if the surface coat is robust enough, the internal parts of the rods will not be penetrated by electrolyte anyway! Solution erupting from the tiny cracks and holes during the heating phases of the vacuum impregnation has left a somewhat rough surface which may not coat smoothly!

I am now doing a third rod with just surface treatment for comparison.

Incidently, the concentration of my Mn(NO3)2 solution as obtained from the metathesis reaction and filtering procedure ended up being about 119.2g in 500mls. That's assuming perfect purity and stoichiometry, so lets say about 226g/litre assuming 95% efficiency. Thats about 1.26 Molar.

Xenoid

nice work

Rosco Bodine - 25-6-2007 at 15:34

Here is some solution data for Mn(NO3)2 pulled from CRC
and a manufacturer label for a 50% solution .

Mn(NO3)2 - 4 H2O m.wt. 251.01 m.p. 25.8C b.p. 129.4C
colorless to pink crystals sol. 100 ml H2O @ 0C 426.4 g.

calculated saturated solution @ 0C
contains 57.76% Mn(NO3)2
(anhydrous basis m.wt. 178.95 )

commercial supplied 50% Mn(NO3)2 in H2O
density @ 25C 1.54

From this data it can be seen that a constant boiling solution
will likely form at 129.4C , or at any rate that temperature
being reached by a boiling solution will contain molten
Mn(NO3)2 tetrahydrate boiling in its own water of crystallization , the solution at 129.4C contains
71.29% Mn(NO3)2 by weight .

For each 100 g. of the 129.4C constant boiling solution ,
an addition of 42.6 ml of distilled H2O will dilute that
71.29% solution to a commercial concentration 50% solution .

I do not have a solubility curve to check this against , but
probably half that amount of dilution water would give much
closer to a saturated solution at room temperature ,
( 58.8%) with little or no crystallization unless it was
cooled to nearly freezing .

My conclusion is that ~15ml dilution water per 100 g. of the
129.4C constant boiling solution would probably be about right , to give a concentrated working solution good for use around room temperature , and that would be a 62% solution of Mn(NO3)2 .

On the temperature , I think you are going to need a bit hotter than 200C ....more like 300-325C range , I have seen stated range from 300C for 5 minutes to 350C for 10 minutes .

BTW ,
There is a possible value for a combined "bimetal spinel"
sort of compound between bismuth and manganese oxides which might form from thermal decomposition of their mixed nitrates or other mixed salts . All I have found so far is that there is a range of mixed oxides of varying proportions that are possible and they are conductive and catalytic , but require a higher temperature for their formation something around 400C . Most of what I have found on this relates to cathodes and supported catalysts , pigments ....but nothing so far turns up in the search concerning anodes .

[Edited on 25-6-2007 by Rosco Bodine]

dann2 - 25-6-2007 at 16:41

Hello,

2c worth...
I guess this process is only useful for Gouging rods as 'better' graphite will not be porous.

Dann2

Xenoid - 25-6-2007 at 17:11

Hi Dann2

No, better quality graphite would be superior, it is still very porous, and the smooth surface would be good for the Dip 'n Bake technique. I'm only using gouging rods because I can currently buy them for about 35 cents each, and also leaving a little Cu plate on the end allows a near perfect electrical connection by soldering or metal clip!

BTW great website, many thanks!

Regards, Xenoid

MnO2 impregnated/coated anodes completed - phew...!

Xenoid - 26-6-2007 at 01:12

I have now completed 12 dip and bake cycles on the two impregnated anodes;

9 cycles of dip, air dry, heat for 15 mins. at 200oC
3 cycles of dip, air dry, heat for 15 mins. at 280oC

I have increased the temperature in accordance with Rosco's recommendations above! I had come across papers using temperatures ranging from 150 - 270oC, I did not realise temperatures above 300oC were used! The temperature control on my hot air gun baking system is not all that accurate anyway, and probably varies by 20 - 40oC from one end to the other!

The rods now have a hard lumpy coating, there is no MnO2 smudge on the fingers when they are run along the rod!

The rods have gained in weight by about 2g, they were about 38g when I started and are now 40g, thats as accurate as I can be as I only have kitchen type scales.

I tried to measure the change in diameter using a micrometer, but the lumpy nature of the coating makes this difficult, it may be as much as .1mm so the coating thickness would be no more than about 50 microns.

Now I have to tidy up my "lab" and carry out some tests!

Xenoid

excerpted notes concerning perchlorate production

Rosco Bodine - 26-6-2007 at 13:45

A couple of things that might be nice finishing touches .
Brush on a final coat having a dopant catalytic for perchlorate
like bismuth nitrate or antimony chloride , or mix one of these
with some of your manganese nitrate and do a final bake .

Also add a soluble phosphate 3 g. / liter to your chloride bath that will be converted to perchlorate .

Justification as follows below ....

From US4072586:
column 5 line 29 :

The anodes of the present invention are also particularly suited for the electrolytic production of perchlorates. A preferred anode for the electrolytic production of perchlorate comprises an electrode with an outer layer of catalytic .beta.-MnO.sub.2 containing from 0.5 to 5.0% by weight of at least one metal selected from the group including As, Sb and Bi.

.beta.-MnO.sub.2 anodes have been tested for the production of perchlorate by electrolysis of an aqueous electrolyte having the following composition;

150 g/l of NaClO.sub.3

450 g/l of NaClO.sub.4

3 g/l of Phosphates and at 40.degree. C and at a current density of 1200 to 1700 A/m.sup.2, and remarkable faraday efficiencies ranging from 70 to 92% were recorded. The best results, namely faraday efficiencies above 90%, have been obtained with .beta.-MnO.sub.2 coatings containing up to 5% by weight of As, Sb and Bi.

The doping agents such as As, Sb and Bi are thought to shift the oxygen potential of the catalytic .beta.-MnO.sub.2 coating above the perchlorate formation potential. This means that the energy gap between the main anodic reaction
ClO3 + H2 ----> ClO4 + 2H + 2e
and the side reaction
H2O ----> 1/2(O2) + 2H + 2e
is increased, therefore increasing the perchlorate faraday efficiency.

[Edited on 26-6-2007 by Rosco Bodine]

Xenoid - 26-6-2007 at 15:36

Sorry Rosco, I don't currently have any Bi, Sb or As salts.

I have just finished making up a 660 g/L solution of NaClO3 it is made with NaClO3 that has been recrystallised 3 times, so should be very low in chloride, I have checked it with methylene blue and it is also free of perchlorate.

I'm planning to run the anode at a current density of 150 mA/cm2 that's about the middle of what you quote above!

Xenoid

[Edited on 26-6-2007 by Xenoid]

Rosco Bodine - 26-6-2007 at 15:57

It should work anyway , just take a bit longer .

How about the phosphate or some phosphoric acid and soda ? TSP powdered detergent would probably work okay .

About the chloride .....I'd try to go to perchlorate
starting from NaCl . A big point about many MnO2 anode patents was the electrolysis of brine so it should hold up okay .

That current sounds about right . They run up to even double that current density on PbO2 . So long as the cell is staying below 60C , keep cranking it up

and cross your fingers . 40C is a pretty safe level and 60C would be about redline .

[Edited on 26-6-2007 by Rosco Bodine]

Xenoid - 26-6-2007 at 17:09

Yeah, I have some potassium phosphate, and I think I can get some Sb and Bi chemicals but at the moment I just want to see if the anode holds together!

We can try adding all the fancy chemicals at a later stage.

I'll use the 2nd anode on some NaCl solution assuming the first one holds together, and makes perchlorate.

Xenoid

Rosco Bodine - 26-6-2007 at 18:49

Quote:

Originally posted by Xenoid
Yeah, I have some potassium phosphate, and I think I can get some Sb and Bi chemicals but at the moment I just want to see if the anode holds together!

We can try adding all the fancy chemicals at a later stage.

I'll use the 2nd anode on some NaCl solution assuming the first one holds together, and makes perchlorate.

Xenoid

It should make perchlorate , but you have to hold your mouth right for it to work

Bismuth fishing sinkers are in the stores . You could make a nitrate from that . It's only a catalyst , makes the efficiency go up a bit .

The phosphate probably ought to go in for either case .
It possibly protects the anode and maybe increases the
efficiency similarly as does persulfate or fluoride for the PbO2 anode or it could be just a wetting agent , I don't know .

[Edited on 26-6-2007 by Rosco Bodine]

Shedding and Shredding

Xenoid - 27-6-2007 at 00:58

Sorry folks, total and utter failure.

Obviously I didn't hold my mouth the right way.

Set up a nice little 800 ml cell, specially designed for testing anodes. Anode - cathode separation (centre to centre) was 40 mm. Cathode was Ti. 130mm of the anode was in the electrolyte with a surface area of about 39 cm2. I used my lab power supply which has a max. output of 4 Amps. Because of this current limitation I only used about 77 mA/cm2 for total current of 3 Amps. The lab supply was operated in constant current mode and for 3 Amps a voltage of 5.4 V was required. Oxygen (and some ozone) were evolved from the anode and there was a whispy pink swirl in the solution for a few minutes. After about 10 minutes, black flakes (some as large as 5mm x 5mm) started to drop off. :mad:

I left the cell running for about another 5 mins, then turned off the current and lifted the anode out, it had slightly pink droplets on the end.
I put the anode back and let the cell run for an hour, by which time there was a pile of MnO2 flakes under the anode, the electrolyte had turned brownish and black carbon particles were floating around!
At this point I turned off the power, interestingly however the anode continued to evolve ?oxygen and shed material for about another hour, even when the electrodes were shorted out! Not sure what was going on at this point, perhaps I have discovered a material which is capable of converting chlorate into chloride and oygen - that must have heaps of practical applications - I could become rich!!

I still think the Dip 'n Bake technique holds a lot of promise, perhaps not on gouging rods however! I still havn't finished the rod that I was just surface coating - it seemed to be forming a much smoother coat, so I'll try that next, and then move onto some other material......

Xenoid

[Edited on 27-6-2007 by Xenoid]

[Edited on 27-6-2007 by Xenoid]

Rosco Bodine - 27-6-2007 at 02:06

It is surprising the coating crapped out that quick .
I am wondering if it is sloughing off loosely adhered
oxide or is it the carbon disintegrating or both .
The erosion may slow down as it goes if it is just losing
outer layers and gets down to more adhered material.

Maybe let it run for awhile longer to make sure .

pH could be an issue too . I was thinking about the phosphate and they are commonly used as buffers ,
so that could be what the phosphate was all about .

When you short the electrodes , you have created a shorted battery of sorts . Leave it open circuit when it is off .

Try baking the second one hotter and longer before you try it . Maybe a finish bake for an hour at 400C or much longer at a lower temperature . The pink swirling could mean you still have some , too much manganese nitrate that didn't change to dioxide . That possibly could be the whole problem . It could be the sulfate impurity from the original material synthesis too . Know you gotta love hearing that .....but it is possible . It is stated in one of the baked
beta manganese dioxide patents that sulfate impurity can kill
the integrity of the layer due to side reactions favoring lower
oxides ....and that could also be the source of the pink swirl .
Even at the best , not all of the nitrate converts to the dioxide , but it is a slightly substoichiometric dioxide with
some monoxide which gives it the added conductivity of a mixed oxide . If the proportional conversion on pyrolysis
is off ....then the required composition is not produced .

The cobalt should work better as it is specifically described effective on graphite , but it would seem like even the manganese should have worked better than it did .

The whole idea of the "activated graphite" is ambiguous
since there are no definite specific examples for the graphite substrate being used at the higher current densities of a perchlorate cell , and on reviewing the patent , the duriron
substrates fared a lot better than graphite and all of the test anodes were being used at a very low current density compared with what a perchlorate cell would encounter .
There may have to be an indigenous metallic oxide on the surface of a substrate to provide a transitional bonding layer
for a baked on oxide , and with carbon there is not that oxide interface which would provide adhesion . To use graphite , maybe a thin film of some intermediate layer which will stick to carbon better is necessary , similarly as is the case for some oxide layers on titanium where only a few materials can be applied directly to the titanium to form an adherent and conductive interface . Or perhaps some doped
or mixed spinel is required for good adhesion to the graphite , that is that manganese dioxide alone won't work ,
but some mixed oxide may be required for a graphite substrate .

It may be that for the current densities required of a perchlorate anode that only a cold process electrodeposition
can provide an adherent and conductive and impervious oxide layer , and that any baked on coating simply has a porosity that makes it vulnerable .

[Edited on 27-6-2007 by Rosco Bodine]

dann2 - 27-6-2007 at 15:34

Quote:

Originally posted by Xenoid
Sorry folks, total and utter failure.

Hello Xenoid,

Commiserations.
Not even a big black mess, but a pink one. They say a change is as good as a rest.

What compound gives a pink colour?

Dann2

Rosco Bodine - 27-6-2007 at 16:01

The pink is evidence of Mn++ , and Mn++ shouldn't be there . It is evidence that not all of the (II) Mn nitrate
was completely decomposed by the pyrolysis .....
not hot enough for long enough to do the job of
oxidizing it to the (IV) Mn of MnO2 .

12AX7 - 27-6-2007 at 17:48

I would be prone to suspect Mn(III)...Mn(II) is a really weak color.

What of Mn2O3? It's the most stable one I think. You can probably melt it in a graphite crucible. It should be pretty easy to pyrolyze your coating to it at a thousand degrees or so. If nothing else, the heat would be good for it. I get the feeling you really just need some diffusion bonding to get it to stick together nice.

Tim

[Edited on 6-27-2007 by 12AX7]

Rosco Bodine - 28-6-2007 at 01:34

Maybe an initial electrodeposition of MnO2 followed by the baked on coatings would have better adhesion .

After further reading ...

It's not too surprising that the baked MnO2 would encounter adhesion problems on the graphite ,
as baked MnO2 doesn't stick to titanium either , even with
the potential there for formation of a mixed oxide bond ,
the MnO2 alone won't attach securely . If a cobalt
oxide is added then it does stick , but the cobalt oxide
spinel is the glue that makes it work , so it is more than
just a dopant for the MnO2 . It possibly requires a
surface oxide interface for the baked cobalt to stick .
And only the electrodeposited cobalt suboxide is actually
reported to stick to graphite . Adding a baked layer
of the ZnCo2O4 spinel on top of that might work , or
the heat might destroy the adhesion of the cold formed layer . The ZnCo2O4 baked on spinel might stick to graphite as an initial coating , if it doesn't rely upon bonding with only an oxides layer . Anyway the , bimetal spinel of zinc and cobalt appears to be very good for a baked coating on titanium , and it might go onto graphite okay alone . Or it might work mixed with a fibrous alumina binder for reenforcement . There may be some different specific conductive spinel type compound which has a better adhesion for graphite .

There's plenty of room for experiments with graphite .

Xenoid - 28-6-2007 at 11:49

Quote:

Originally posted by Rosco Bodine
Maybe an initial electrodeposition of MnO2 followed by the baked on coatings would have better adhesion .

After further reading ...

It's not too surprising that the baked MnO2 would encounter adhesion problems on the graphite ,
as baked MnO2 doesn't stick to titanium either , even with
the potential there for formation of a mixed oxide bond ,
the MnO2 alone won't attach securely .

That was my reasoning for doing the vacuum impregnation / baking cycles, I figured MnO2 crystallites forming in the pore spaces would have a good mechanical bond to the carbon rod, and the surface coating would be bonded to these. Sort of like having "fine penetrating roots" to use a gardening analogy! Also, because the gouging rods are so crappy (full of holes and pores) this might actually be an advantage over high quality graphite.
I had previously tried plating MnO2 at 5 mA/cm2 using the recipe on Dann2's pages (MnSO4 in dil. H2SO4) but it did not adhere, in fact it didn't even seem to form!

I am currently giving the 2 remaining rods extra coats at 320oC for 30 mins.

Don't hold your breath.......

Xenoid

Rosco Bodine - 28-6-2007 at 22:28

I don't know if it would be of any use in this application , but there is a conductive bimetal manganese chromite spinel that can be formed in situ I am pretty sure from manganese nitrate and ammonium dichromate .....followed by heating to ignition of the dried intermediate which undergoes an exothermic decomposition to leave a glowing hot residue of the combined oxides . It may just be a good way of blowing up the porous carbon rods when you want to try something radical

When I was reading about this , it struck me that it might be possible to use this reaction as a heat source in some sort of mixture of oxides which might form a melt from its
own heat of reaction .....and possibly making a conductive ceramic anode would be as simple as pouring the granular precursor in a mold and baking it up to the ignition temperature .....or maybe using some thermite as a primer and lighting the fuse

to produce a self casting
ceramic anode

Beaters - 29-6-2007 at 08:52

A couple of questions:

1) Anyone ever try the type of carbon rods used in arc lights (search lights, some cinema projectors)? I have a few of them. I'm not sure how they were made but they are quite hard, about 1/4 inch diameter and maybe 20 cm long.

2) Any thoughts concerning the merits of various types of power supplies for small scale chlorate / perc production regardless of the choice of anode(s)?

Xenoid - 29-6-2007 at 13:54

Quote:

Originally posted by Beaters
A couple of questions:

1) Anyone ever try the type of carbon rods used in arc lights (search lights, some cinema projectors)? I have a few of them. I'm not sure how they were made but they are quite hard, about 1/4 inch diameter and maybe 20 cm long.

2) Any thoughts concerning the merits of various types of power supplies for small scale chlorate / perc production regardless of the choice of anode(s)?

I guess they would work (for chlorate), but they may have fillers to harden them or produce more light.

For a first experimental cell, carbon anodes from a lantern battery (zinc-carbon not alkaline!) are a good choice, so you can learn about all the problems of running a chlorate cell. I searched around all the local recycling centres, pulling the old batteries out of the lanterns. These carbon rods are already impregnated with a waxy material. They are a bit short so you will need a fairly low plastic food container or similar, holding about 500 - 600mls. My first cell had four and later eight rods in a circular pattern, surrounded by a stainless steel cathode. The carbon rods were inserted through 6mm rubber grommets and the electrical connections were made using fuse clips or tool clips, if the brass tops are OK you can solder directly to them. Run the cell at about 2 Amps. Make sure you have an ammeter (the 10Amp setting on a small cheap digital multimeter is fine) otherwise you won't have a clue whats going on with cell. The best bet for a small cell like this is a small variable lab power supply otherwise a 6volt transformer with a bridge rectifier, run of a variac, but you probably don't have a variac! A small cell like this only requires about 3.5 volts to produce a current of 2 Amps, so if you hook it up to a 5 volt computer power supply it will probably vaporize.

You will need a high wattage resistor to drop the voltage. (Use Ohm's law). You can use nichrome wire from an old heater or toaster, or carbon rods wired in series, ( a stripped gouging rod has a resistance of about .1 - .15 ohms).

Most importantly, read all the websites dealing with home chlorate production.

[Edited on 29-6-2007 by Xenoid]

Chlorate_Cell.jpg - 108kB

Beaters - 29-6-2007 at 15:40

Thanks for the feed-back. Nice photo.

MnO2 coated gouging rods - the final indignity!!!

Xenoid - 30-6-2007 at 22:20

Greetings,

Well I gave my remaining two gouging rods extra coats at higher temperatures - taking on board Rosco's advice.
I won't bother going into details, suffice to say it was a large number, the final coats were baked for 30 mins. at 320oC.

For the electrolysis, I used 500g/litre pure NaClO3, with a Ti cathode.

I tested the impregnated rod first, starting at a cell current of 1 Amp (25mA/cm2) voltage required was 3.8V, Hmmm... looked good, (It had that characteristic low oxygen production and small bubbles, like my Pt anodes). Let it run for about 20 mins no flaking!
Turned the current up to 2 Amps (51mA/cm2), Voltage 4.5V. Solution had a slight pink tinge. I let it run for 40 mins, still no flaking, but solution was now distinctly pink!
Turned up the current to 3 Amps / 4.9V ( about 75mA/cm2) solution now rosy pink! One hour later and the anode was shedding. :mad:

I then connected the rod that was just coated (not impregnated) it had a much smoother surface. I ran it at 2 Amps / 4.1 Volts but after 6 hours it too had started shedding, by this time the electrolyte was a rich, rosy bergundy colour, very pretty!

Whilst they were working, the anodes seemed to behave in a similar fashion to Pt. With a tripling of the current there was very little increase in oxygen production, indicating that the current was going into perchlorate production, (greater efficiency at higher current densities). Does that sound right?

I can understand why the anodes are failing mechanically, and shedding flakes of MnO2 and carbon, but why am I getting so much Mn++ in solution, I don't believe it is all coming from unconverted Mn(NO3)2.

WARNING - Anyone messing with MnO2 anodes, it is a real chore to get rid of the Mn from your chlorate, the solution keeps precipitating brown and black crud during the concentration and crystallisation phases, despite much filtering and removal of the bulk of the Mn by precipitating with Na2CO3!!

Xenoid

Rosco Bodine - 30-6-2007 at 23:06

Hmmm...I'm starting to wonder if your pink might actually be formation of *per*manganate ???? Maybe if you go above a certain voltage , it is like a breaking point ??

You follow what I mean , you may be overdriving the anode and actually oxidizing the anode itself instead
of what you are trying to do the work on that is in the electrolyte .

It could be that the electrode gap being wide is causing you to use too much voltage to get good current ,
pushing the voltage up to a point that the potential is actually attacking the anode coating from underneath ,
at the carbon to MnO2 interface ? ...or at any rate
wherever it is occuring , maybe the overvoltage is what is killing the coating and you have to run the gap much closer to keep down the voltage much lower .

[Edited on 1-7-2007 by Rosco Bodine]

Xenoid - 1-7-2007 at 00:18

Quote:

Originally posted by Rosco Bodine
Hmmm...I'm starting to wonder if your pink might actually be formation of *per*manganate ???? Maybe if you go above a certain voltage , it is like a breaking point ??

[Edited on 1-7-2007 by Rosco Bodine]

So if there is sodium permanganate in the solution, and I add NaCl, it will be oxidised to NaClO3 and MnO2 will be precipitated, according to my chemistry book.

Xenoid

Permanganate!

Xenoid - 1-7-2007 at 00:49

Yeah!

Just tried this, made the solution alkaline by adding NaOH, and added NaCl, the distinctly pinky-purple colour has disappeared, and browny/black crud MnO2 has precipitated!

So where to from here, shall I make another anode and try it at a lower voltage - what is the limiting voltage!

Xenoid

Anodes

MadHatter - 1-7-2007 at 07:10

http://cgi.ebay.com/Potassium-Perchlorate-Machine_W0QQitemZ2...

This eBay seller claims the machine will produce KClO4 but is offering COPPER anodes.
I can't believe it would work.

A couple of sellers are offering platinum-coated anodes for $95-100 each. Too rich for
my blood.

I'm not sure if we'll ever find the 'perfect' anode. I made some more 'perc' recently.
I had a thin coating of PbO2 over the gouging rod this time around but even that was
torn up by the electrolysis. The perchlorate cell has to be one of the most hostile
environments there is in electrochemistry. Pinholes in the PbO2 layer are probably the
cause of this destruction. It's like a shark smelling blood after the 1st bite, and the
feeding frenzy occurs.

BTW, a snapshot of the gouging rods I use before peeling the copper plating.

[Edited on 2007/7/1 by MadHatter]

GR.jpg - 168kB

limiting overvoltage found charted in CRC !

Rosco Bodine - 1-7-2007 at 07:17

@Xenoid

This relates precisely to something brought up about
ripple voltage and electrode potentials causing mixed products in another thread , and it seems the anode material itself can certainly be affected also . Never really thought about this much , but it does make sense .
Thinking back on it , there is an engineering parameter
concerning a sort of "anode depassivation voltage" ???...but I can't remember the correct/exact term for it or even where I read it .....I think it was in one of the cathodic protection patents where the parameter was mentioned for duriron anodes that perform excellent up to a certain "depassivation?? voltage" which is the limit
for noncorroding operation .

I have not a single Electrochemistry book to reference
and find what is the minimum ( anode ) oxidation potential on a chart for the formation of permanganate ,
but evidently that's going to be the defining limit for
operation of an MnO2 anode coating to keep it from entering the reaction itself .

You might have to close the electrode gap down to 3 mm or so , where there is a risk of the thing shorting out from any flaking , so you will absolutely require some sort of active current limiting PS to babysit the process .

As an interesting side note ...MnO2 can also be formed
as a product from Mn(NO3)2 and permanganate ,
and IIRC the MnO2 first forms as an unstable hydrated sol / gel system and then precipitates a nanocrystalline
*beta* MnO2 in a similar way as can magnetite be gotten
as a nanocrystalline form by chemical means . These
processes are generally applied to precipitation on
carriers for use as catalysts following calcination to sinter
the carrier to the carried particles of catalyst , and are also
processes for ink and paint pigments ....but might have some adaptive use to electrode manufacture as well .
The only problem I can see is that with using Mn(NO3)2
and an alkali permangante is the KNO3 byproduct could
cause ignition of the carbon on baking , so another Mn
salt like an acetate would probably be a better choice if
it reacts the same way with permanganate . This might
eliminate a lot of baking time and achieve a more complete conversion at a smaller grain size for the MnO2 .
Never tried it and never read anything specifically describing this for anode application ....but haven't really searched for it either , so it might already be a known
technique , or something for a logical experiment .

For the cathode , here's a thought . Maybe get or make some plastic washers as a spacer for a coaxial arrangement
of bare wires spaced parallel to the center anode , put about
eight of them around it . Make the holes in the spacer washer for the wires a little small so it is a press fit to hold
them like a birdcage around the anode , very closely gapped
like 2-3 mm . Or you might use PVC fittings as a spacer for
some sort of metal tube as the cathode with the anode spaced inside it with three point support at 120 degree spacing to keep the anode centered coaxially top and bottom .

Edit : CRC gives the following reaction potentials :

ClO4 + 2H + 2e <----> ClO3 + H2O 1.19 volts

MnO4 + 4H + 3e <----> MnO2 + 2H2O 1.679 volts

I interpret that as meaning if you go one half volt too high ,
your MnO2 anode is toast .

Your overvoltage limit is 0.489 volts ( above the minimum 1.19 volts for perchlorate production ) so you only have ~ 0.4
volts allowable increase beyond where perchlorate production begins , before you start also destroying the anode .

[Edited on 1-7-2007 by Rosco Bodine]

Xenoid - 1-7-2007 at 13:49

Damnation!

Now the black/brown precipitate has settled, the solution is actually a bluish/green!!!

Manganate I assume, how do I get rid of this!!

Re. above voltages, the cell starts to conduct at about 2.4V, thats with a 40mm electrode spacing, so maybe 10 - 20mm spacing would be OK, but at quite low currents. Less than 5mm and the electrode would be just about in the hydrogen stream coming of the cathode.

Xenoid

[Edited on 1-7-2007 by Xenoid]

chlorine evolution potential

Rosco Bodine - 1-7-2007 at 15:30

You need to get some circulation flow going , to strip that plume of hydrogen down to a thinner section so you can close up the gap for an MnO2 anode ...as a wide gap is intolerable given the narrow voltage gradient between
perchlorate production and anode destruction . This is simply an inescapable materials limitation which is going
to apply to MnO2 being used as the anode material in a perchlorate cell .

And as if the precise voltage for ClO3 to ClO4 is not exacting enough .....let's see what else applies as a possible complication . If I understand this correctly , the plot is thickened by possible unwanted cathode reactions which can reverse the direction of desired reactions if the cell voltage and pH isn't just right .

This is interesting , there are a couple of possible
chlorine discharge potentials listed in CRC that are *intermediate* values between the two above , which
I will show again for location in the range and it appears
that the both the ClO3 and ClO4 ion can actually be reduced again all the way back to chlorine in an undivided cell where such ions are exposed to the cathode . It would seem an acidic pH would favor this undesired result , as some alkalinity would immediately react with the molecular or ionic chlorine and keep it in the reaction . However that might also
encourage the undesired reaction so this could be only minimzed by careful voltage control and a near neutral pH ,
in an undivided cell .

ClO4 + 2H + 2e <----> ClO3 + H2O 1.19 volts

ClO4 + 8H + 7e <----> 1/2Cl2 + 4H2O 1.34 volts

ClO3 + 6H + 5e <----> 1/2Cl2 + 3H2O 1.47 volts

MnO4 + 4H + 3e <----> MnO2 + 2H2O 1.679 volts

Concerning your evidence of some Mn++ residue that would make sense , because following the oxidation of the MnO2
to MnO4 at 1.679 volts , MnO4 itself is further reduced
according to :

MnO4 + 8H + 5e <----> (Mn++) + 4H2O 1.491 volts

It is a certainty you would find Mn++ compounds in the electrolyte after disintegration of an MnO2 anode , and the
permanganate was something that existed only as a transient intermediate species during the MnO2 decomposition .

Electrochemistry is one of my lesser areas of understanding ,
so if I have gotten this wrong or misunderstand the values
interpretation , anyone feel free to speak up .

DerAlte - 1-7-2007 at 20:52

@ Rosco - electrochemistry is understood by academics, but electrolyses only by artists! Don't belittle yourself: quote " Electrochemistry is one of my lesser areas of understanding..." I'ms ure you have a better grip on the theory than most. Being a retired EE, I am always fascinated by electolytic methods, whose power can exceed any chemical means. Think of fluorine or Li,K, Cs, Rb etc. it's the only way to go.

DerAlte

Rosco Bodine - 2-7-2007 at 08:07

The voltages given above are not absolute cell voltages
like you would read across the power supply leads with a voltmeter , but are difference voltages compared to a
"standard hydrogen electrode" which is a deliberately polarized platinum electrode being operated in a 1 M HCl
electrolyte as a laboratory "standard" and how standard it is seems to depend on whose laboratory is making and reading it

......since every printed table of redox potentials seems to vary from the next

. However
the tables in CRC were all done by the same person in the same lab using the same equipment , so their relative
values show something useful , in terms of the "spread"
of measured voltages which have detectable effects .

The "absolute voltage" of the standard hydrogen electrode is not so absolute from one lab to another ,
except as the reference used for experiments in that
particular setup . But I have seen typical values for
that absolute voltage ranging from 4.2 volts to 4.8 volts ,
and while experimental conditions relate to one molar electrolytes , obviously the concentration differing and
the electrode spacing would affect the actual cell operating voltage and the actual discharge potentials ,
as I understand it anyway . So these charted values
for electrode potentials are ambiguous values which
do not directly translate to a cell of different design
and different content .

Neither is the catalytic effect of electrode materials
which may be specific and preferential for certain reactions addressed by such tables , where the actual production cell may be using electrode materials and
process catalysts in the electrolyte also which can shift
the standard potentials several tenths of a volt in
a favorable direction for selectivity of the desired product .

So considering these things , must be done while "reading" such tables . What I get from such
reading of the table above is that the desired cell operating point would be found by slowly increasing the voltage until chlorine evolution is barely detectable as a byproduct and that would correspond to reaching an
electrode potential for your cell , which is parallel to
the second reaction above . Regardless of the absolute numbers , you know then that the voltage reading for your cell and your electrolyte has reached a level where
some of the perchlorate being produced at the anode
is being reduced again at the cathode as evidenced by the chlorine being evolved .

This is a point where certain electrolyte additives can form a film on the cathode which obstructs contact of the electrolyte with reactive ionic hydrogen which reduces
the perchlorate as a competing reaction , favoring the
ionic hydrogen instead combining to form molecular hydrogen and escaping as bubbles unstead of reducing
the just formed perchlorate which is desired to remain intact . This additive could be dichromate and magnesium chloride in very small amount , like 0.1 g per liter , and there are specific combinations of different materials used depending upon what is the electrode materials used in the particular cell , materials which basically form a conductive semi-solid permeable membrane film on electrodes and steer the reaction towards the desired products and/or interfere with production of the undesired byproducts . Such additives
emulate the function of a divided cell by forming a porous
barrier layer on the surface of the electrode , interfering
with the surface chemistry which would otherwise occur there on the cathode particularly , by shielding the nascent
ionic hydrogen from contact with the electrolyte just long enough for it to spontaneously combine with itself to form much less reactive H2 .

[Edited on 2-7-2007 by Rosco Bodine]

Xenoid - 2-7-2007 at 13:02

Quote:

Originally posted by MadHatter

A couple of sellers are offering platinum-coated anodes for $95-100 each. Too rich for
my blood.

[Edited on 2007/7/1 by MadHatter]

I just ordered a 60mm x 90mm platinised titanium electrode from Palloys;

http://www.palloys.com.au/category7_1.htm

It was about $81 Australian, but I just got an email to say that the price had gone up and the new price was A$97 + A$5 postage (their supplier had increased the price).

Looks like there are too many people out there making perchlorate.....

They have a smaller one for about A$50, not sure if the price has gone up on this one, or not.

Xenoid

garage chemist - 2-7-2007 at 14:05

Have you tried the thermal disproportionation of chlorate at least once before spending so much money on a perchlorate anode?

Today, another member on the german forum has tried my method of thermal chlorate disproportionation and found it to work very well. He used KClO3 from a graphite anode chlorate cell which was still wet and dirty.
The thermal disproportionation tolerates any amount of chloride contamination and seems to be less sensitive to heavy metals as I previously thought (there was slight MnO2 contamination in the KClO3).

You can even recycle the KCl byproduct by boiling down the filtrate from the residual chlorate destruction step.

I keep repeating that the thermal disproportionation works well and gives reasonable yields without the need for pure chlorate and any anodes.

Eclectic - 2-7-2007 at 14:13

It sort of depends on whether your primary interest is in the journey, or the destination, grasshopper.

May the electromotive force be with you.

[Edited on 7-2-2007 by Eclectic]

Xenoid - 2-7-2007 at 14:49

Yes, unfortunately my primary interest has now become the journey....

The combination of thermal + chlorate + disproportionation + perchlorate sort of scares me, so no I havn't tried it, but I am aware of the process!

Xenoid

more on baked cobalt spinel US4368110

Rosco Bodine - 3-7-2007 at 00:43

The idea of a possible baked coating on graphite keeps coming back to a cobalt spinel as something more likely
to stick to graphite , less likely to flake off , and more
resistant to chemical attack in a perchlorate cell .

I have been reading patents related to these cobalt spinel
coatings and found another Dow patent which shows a
series of test coatings which were actually baked onto a
frosted sandblasted pyrex glass substrate . If this tertiary
spinel formed from the baked nitrates of cobalt , zinc , and magnesium in a molar ratio of 6:2:1 will stick to glass then it
is likely it will stick not only to graphite but even more likely it will stick to a porous ceramic , or perhaps sinter and cement
together particles of itself having been formed in bulk powder separately , or better yet might be used to cement doped tin oxides into a massive anode which can be sintered , cemented together at a reasonably low temperature .

*If* the conductance value stated in the patent has been calculated for a cubic centimeter , ( I am not clear on their measurement result , is the mho value for a square cm of the conductive film , or calculated for a cubic cm of the film from its known thickness ? ) .......
This stuff isn't conductive enough to use en masse alone ,
but possibly it could also be used to cement together particles of metal , in a sort of metal / spinel composite .
The metal would provide the needed conductivity and the
tertiary spinel would provide the chemically resistant continuous phase matrix .

Ebonex .... move over .
Here's a new conductive ceramic substrate . ( Maybe )

Twospoons ought to love this one

[Edited on 3-7-2007 by Rosco Bodine]

Attachment: US4368110 Zinc and Magnesium Substituted_cobalt_oxide_tertiary_spinel.pdf (152kB)
This file has been downloaded 747 times

Antimony doped Tin Oxide / MnO2 tertiary composition

Rosco Bodine - 3-7-2007 at 14:44

@ Xenoid

Here's something 100% OTC that might stabilize the baked MnO2 on graphite .

From US2564707 which also charts the conductivity for various Sb doping percentages on SnO2 ......

See example 2 , and 9 and 10 . The solution of example 2
applied to your baked MnO2 graphite , and then baked again , maybe three coats ......should form the ternary
composition similar to 9 and 10 . And this should be far more
adherent than the MnO2 alone .

Alternately you could try coating graphite from the start with the composition of example 2 or 9 . If this scheme follows the same pattern as does the toughening of the coating
for the cobalt spinels , then the added second and third
dopants results in a more adherent coating . These doped tin oxide compositions also reportedly stick to glass .

The antimony doped tin is good , and is OTC from the 95/5
wire solder which may be dissolved in hot HCl . Anyway
it is a logical alternative to cobalt , and should fare better than MnO2 alone .

Attachment: US2564707 Sb2O3 doped SnO2 and tertiary compositions.pdf (479kB)
This file has been downloaded 772 times

Twospoons - 3-7-2007 at 15:18

Spray coating onto a heated substrate looks interesting as a way to quickly build a thick layer. Wonder if it it would work with the cobalt spinels?

I think I'm going to have to put you on my Christmas card list, Rosco.

[Edited on 4-7-2007 by Twospoons]

Eclectic - 3-7-2007 at 15:29

As posted earlier, you need to add some H2O2 to the 95/5 solder dissolved in 10-12N HCl to get the antimony residue to dissolve and convert the SnCl2 to SnCl4, otherwize you will get an insoluble precipitate. Yellow SbOCl3 color remaining persistent after 1 hour at 90-95C indicates enough H2O2 has been added.

Rosco Bodine - 3-7-2007 at 16:40

Quote:

Originally posted by Eclectic
As posted earlier, you need to add some H2O2 to the 95/5 solder dissolved in 10-12N HCl to get the antimony residue to dissolve and convert the SnCl2 to SnCl4, otherwize you will get an insoluble precipitate. Yellow SbOCl3 color remaining persistent after 1 hour at 90-95C indicates enough H2O2 has been added.

Yeah the ratio of Sb to Sn has to adjusted to optimum also ,
and IIRC you have already described how to do that .
We need to collect and condense the finer points of this
collective research into a summary member publication ,
if dann2 isn't already working on it .

There was a tertiary chromium containing doped tin oxide example #22 in the above patent which really caught my notice as a possible candidate coating for an *aluminum*
substrate , as I already posted a patent relating to a conductive chromate anodization for aluminum which might be a compatable interface . A similar thing might be possible on a stainless steel interface , as an alternative to titanium .
Likewise is #21 interesting for a possible copper substrate ,
and #17 for iron ...even if it was a temporary substrate application . #17 might also work as a baked binder for a nanocrystalline magnetite filler material .

These tertiary doped tin oxides would likely
weld by fusion nicely to any parent metal substrate which could contribute the minor oxide dopant as an indigenous , nascent surface oxide , or having the minor dopant as an already existing mixed oxide primer , as with the chromate .

[Edited on 3-7-2007 by Rosco Bodine]

Eclectic - 3-7-2007 at 18:00

That last patent you posted, as well as the papers I referenced seem to indicate that the 95/5 Sn/Sb ratio in the solder is almost right on the money for the lowest coating resistance. Things may be a bit different for coatings on titanium baked at 450C, so some experimentation is in order.

Rosco Bodine - 3-7-2007 at 22:55

Quote:

Originally posted by Eclectic
That last patent you posted, as well as the papers I referenced seem to indicate that the 95/5 Sn/Sb ratio in the solder is almost right on the money for the lowest coating resistance. Things may be a bit different for coatings on titanium baked at 450C, so some experimentation is in order.

I have been doing the calculations involving molar conversions and percentage compositions and the
95/5 alloy will be a bit rich in terms of Antimony concentration , 4.7285% of Sb2O3 dopant in the composite total , about double to three times the concentration it needs to be for a minimum resistance composition .

Example #2 of the patent is 1.4647% Sb2O3 for example which is less than a third of the antimony content of 95/5 .

For purposes of calculation the percentage of Sb2O3 derived from the antimony of a tin antimony alloy converted to the chlorides SnCl4 and SbCl3 and then to the oxides on baking ,
is 94.57% of the percentage value based on the metals .

For example , a 5% antimony / tin alloy will become a
5 X .9457 = 4.7285% Sb2O3 / SnO2 composition .

The amount of free tin to be added to dilute the antimony
concentration to whatever is desired should be easily calculable from there .

Eclectic - 4-7-2007 at 05:47

But many of the later patents regarding Sn/Sb oxide on Ti for electrolysis anodes use 5-15% Sb. One of the most recent says 5% is optimal for lowest resistance. SbCl3 is volatile, so maybe the excess bakes off? Or maybe there is an interaction with residual surface TiO2.

[Edited on 7-4-2007 by Eclectic]

Rosco Bodine - 4-7-2007 at 08:07

Quote:

Originally posted by Eclectic
But many of the later patents regarding Sn/Sb oxide on Ti for electrolysis anodes use 5-15% Sb.

Yeah I noticed one of the Dow patents US4369105 ,
concerning cobalt spinels which actually shows a conductivity related chart of a sort uses a 16.6% Sb2O3 composition .
But there is no indication that they were optimizing conductivity in regards to that percentage of Sb2O3 dopant ,
but were surveying the effect of bake times and the presence or absence of the intermediate layer . Compared
with the actual conductivity data for the different percentage
of dopant as charted in the Corning patent US2564707 ,
the test coating for the Dow patent is using more than ten times the amount of dopant which would provide best conductivity . Perhaps it is different when a titanium substrate below and a subsequent spinel layer above sandwiches the doped tin oxide intermediate layer , and some of the dopant Sb2O3 may actually leach from the intermediate layer , skewing the figure for what is an optimum percentage , in comparison with what is the case
for a glass substrate and no other coating than the doped tin oxide alone .

Quote:

One of the most recent says 5% is optimal for lowest resistance.

Actually I didn't notice which specific patents surveyed the
effect of different percentages of Sb2O3 , on an intermediate layer to find the optimum for conductivity , adhesion , ect .
I'm sure I saw one or more patent that described the adhesion value of coatings of some sort in terms of abrasion tests , but the numbers escapes my recollection and I didn't make any special note of it for later reference . If you have the patent numbers related to conductivity for the dopant percentages please share them . It was probably
in some of the ruthenium or other precious metal usage patents which I sort of scanned over more quickly and discarded for my preference and more intense interest in
alternatives which used more common and less expensive
materials . Damn I do not want to go back an reread a dozen more patents to find it again .

Quote:

SbCl3 is volatile, so maybe the excess bakes off? Or maybe there is an interaction with residual surface TiO2.

The more I think about it , the more dubious I am about any leaching effect changing the percentage of dopant so drastically for an intermediate layer . The whole matter
is probably nitpicking an insignificant detail and 95/5 would work fine as is for what we are doing . The difference in conductivity wouldn't be significant unless you were building up thirty coats of the stuff or using it for a fusible binder in some massive coating or massive composite scheme . 95/5 may not be perfect , but it's close enough for government work

Anyway I worked out the conversion multiplier so it can be plugged into the equation to formulate whatever modified
percentage of dopant is desired , starting from the alloy .

Eclectic - 4-7-2007 at 10:34

I just noticed that Sn and Sb were right next to each other on the periodic chart and figured the difference in atomic weight for this application was insignificant.

This paper gave me the idea to add some ammonium bifluoride if I decide to deal with the additional hazard:

http://www.blackwell-synergy.com/doi/abs/10.1111/j.1151-2916...

"Thin films of antimony-doped tin oxide have been obtained by a new technique, the so-called hydrolysis deposition method, in which hydrolyzed solids are precipitated from metal fluoride solutions. Mixed solutions of SnF3 and SbF3 produce antimony- and fluorine-doped tin oxide films. The amount of antimony can be controlled in a wide range by adjusting the initial fluoride concentrations of the solution. The film containing 2.9 mol% antimony heated at 500°C has an electrical resistivity of 1.0 × 10-3Ω·cm, which is lower than previously obtained by wet-chemical techniques."

And these patents: US3865703, US3917518, US4040939

Quote:

Originally posted by dann2

Quote from US Pat. 4,040,939:
A solution for the semi-conductive intermediate coating was prepared by mixing 30 milliliters of butyl alcohol, 5 milliliters of hydrochloric acid (HCl), 3.2 grams of antimony trichloride SbCl.sub.3), and 15.1 grams of stannic chloride pentahydrate (SnCl.sub.4.5H.sub.2 O).

A strip of clean titanium plate was immersed in hot HCl for 1/2 hours to etch the surface. It was then washed with water and dried. The titanium was then coated twice by brushing with the solution described above.
The surface of the plate was dried for ten minutes in an oven at 140.degree. C. after applying each coating. The titanium was then baked at 500.degree. C. for 7 .+-. 1 minutes.

The theoretical composition of the semi-conductive intermediate coating thus prepared was 81.7 percent SnO.sub.2 and 18.3 percent antimony oxides (calculated as Sb.sub.2 O.sub.3).

End quote:

Starting with 95/5 solder, HCl, H2O2, the materials are so cheap, you could do first acid etch step and coating in the coating solution itself without any alcohol added.

Sort of like "Zinc"ateing aluminum, you would be "Tin"ateing the titanium.

[Edited on 7-4-2007 by Eclectic]

A reduced chloride content method

Rosco Bodine - 4-7-2007 at 11:25

US6777477 describes a method for a 6.36% Sb2O3 doped SnO2 coating which is better than the Corning patent US2564707 in film thickness , and is also deposited on a glass substrate .

This method uses an ammonia derivative and a PVA thickener
to obtain a heavier loading . Microscopic examination of the
transparent films on glass was used as a basis for grading
the continuity and quality of the conductive films produced .
This might should have usefulness as a first coating
on titanium .

The use of a thickener was disclosed also in the Diamond Shamrock patent US4243503 Example#2 with regards to thickening of a suspension of antimony doped tin oxide which had been previously calcined from the sulfates and mixed with 50% Mn(NO3)2 . The patent also disclosed the mixing of powdered titanium into the suspension which produced the most long lasting of the tested baked coatings .

I think in particular where heavier loadings are needed like building up on a porous substrate , that these modifications could be very useful . The reduction or absence of chloride might be helpful also in experiments with alternative substrates . I keep thinking it would be wonderful if this magic could be worked on something else more commonplace than titanium ....something like aluminum perhaps .

This is probably *state of the art* for use of the 95/5 alloy
chlorides as an intermediate layer . The ammonium derivative produces a better dispersed solid solution for use of higher percentages of antimony and produces a tougher and more perfect coating . This patent was primarily intended for optical grade coatings so you know it has to produce a virtually flawless coating , and it is a recent patent .

It reminded me of an older patent US4775412 which uses
a similar but separately isolated ammonium derived intermediate , which goes into some lengthier decription
of a more involved process , which is considerabley simplified by the more recent patent .

[Edited on 5-7-2007 by Rosco Bodine]

Attachment: US6777477 Sb2O3 doped SnO2 via ammonia soluble derivative.pdf (67kB)
This file has been downloaded 1434 times

Spinel possible product of ignition

Rosco Bodine - 7-7-2007 at 21:08

The possibility of forming a conductive spinel as the product
of an exothermic decomposition reaction has appeared
once again . It would be very convenient if a mixture of the
precursors decomposed with sufficient heat energy that
the desired spinel would form spontaneously , without any need for long baking of mixed oxides . The ash from ignition
could possibly be the desired spinel in a microcrystalline form .

I was reading US3711397 concerning bimetal spinels and
it was mentioned that the cobalt aluminate spinel CoAl2O4
is one of the most conductive and particularly desirable spinels .

Another patent US3066139 (attached) was recalled from an earlier post on another topic in energetic materials , concerning a high energy fuel which is a condensation product of hexamine and aluminum nitrate , which upon ignition produces a finely divided and highly active alumina as the product of a vigorous exothermic reaction . A supplemental oxidizer
can be mixed with the hexamine - Al(NO3)3 to increase the
energy of the reaction further , and it was my idea that
perhaps Co(NO3)2 being that added oxidizer might result
in the cobalt aluminate spinel CoAl2O4 being the product
instead of plain Al2O3 alumina as would be the case in
the absence of the added cobalt compound .

Reaching further with this same idea , it seems likely that the antimony doped tin oxide mixture which is derived from the ammonium stannate / ammonium antimonate precursors and fuses to a conductive glass , could be used as a relatively easily melted binder mixture with the preceding composition ,
to form a filled melt or sintered composite anode .

Attachment: US3066139 Hexamine Al(NO3)3 HIGH_ENERGY_FUEL.pdf (160kB)
This file has been downloaded 823 times

not_important - 8-7-2007 at 00:19

Why not just go with cobalt oxide, Al powder, and say ammonium nitrate, aluminium nitrate, or a basic aluminium nitrate? or the oxalate

CoC2O4 + 2Al + 2 NH4NO3 => CoAl2O4 + 2 CO + N2 + 4 H2O (or whatever CO/CO2/H2O/H2/N2/NOx mix results)

The oxalate is easy to make, the oxide tend to pick up oxygen to give "Co3O4" and then "Co2O3", which might make it difficult to get the optimal ratios just because you'd not be sure of the composition of the oxide.

Rosco Bodine - 8-7-2007 at 05:30

Yeah there indeed could be several aluminum spinels possible from reactions which are similar to thermite ,
or as a parallel reaction utilizing its heat perhaps along with the heat of reaction forming the spinel .

I keep thinking that it may well be possible to have an exothemic enough reaction from specific combinations
of precursor materials that ignition of a sufficent quantity as might be useful for a modest sized anode , possibly even result in a self-melting composition . It would be something like a thermite welding / casting scheme where the composition of the oxide slag is what is the product of interest .

It's probably too easy to be true , having a powdered, instant, " anode in a bag " .....
pour it in a mold , stick a fuse in it and light it

,
let cool and attach wire and use .

Compared with some of baking schemes , the idea does have a certain appeal , .... steer the outcome of a reaction which certainly generates plenty of heat by itself , instead of working with more inert precursors and applying brute force external heating to them .

not_important - 8-7-2007 at 06:04

Nickel might be able to replace cobalt in that application, making it bit less expensive. The trick is to get enough oxygen without generating too much gas that blows the hot mixture apart. Heating cobalt oxide in O2 under pressure can push the overall composition up to CoO2, although it seems to be an absorption rather than actual Co(IV); but that's not enough oxygen to form the spinel.

And lithium-doped nickel oxide is a semiconductor, add more lithium to lower the resistance. Make it with standard pottery technology, mix nickel and lithium carbonates well and heat. Not self-firing, but simple and fairly inexpensive.

Some Bed Time reading

dann2 - 10-7-2007 at 09:36

Hello,

I scanned the following from Electrodes of Conductive Metallic Oxides. Sorry about the terrible bad presentation.

http://llwolly.angelfire.com/index.html

and the adds.
You are going to have to save images and rotate.

It is essential bed time reading.

Dann2

Xenoid - 10-7-2007 at 12:22

Thanks for that information Dann2, the MnO2 stuff was interesting, I will continue my experimenting with MnO2 coating of graphite/carbon. I now have several dozen lantern battery rods, so I can make some "mini-cells", which will not be so demanding on reagent quantities. I am about to "purify" my Mn(NO3)2 by precipitating the CaSO4 remaining in solution, using BaCl2.

The following caught my eye:

"......amalgam cells at 10kA/m2 and with a distance of 3mm between anode and cathode...."

Wow!!!... I didn't realise industry used such extreme parameters!

Xenoid

[Edited on 10-7-2007 by Xenoid]

Anybody try anything with cobalt yet?

jpsmith123 - 11-7-2007 at 17:27

I got some cobalt sulfate recently, so I may try to see how well the oxide can be plated onto a piece of titanium...maybe over the weekend I'll give it a try.

dann2 - 12-7-2007 at 06:26

Hello Joe,

I think you will be the first on the Cobalt front, if I am not mistaken.

Rosco Bodine - 16-7-2007 at 06:56

@jpsmith123 ...

Other than that US3399966 patent which caught your notice ....please check out the possibility concerning the
cobaltous acid gotten from H2O2 and Co(OH)2 acting as a sort of "Cold Blue" on clean titanium , as a preface for any baked coatings . Cold Chromating might also have a benefit on clean titanium that is to subsequently receive baked coatings , particularly where non-chloride precursors are used .....as the cold treatment could serve to limit the thickness and oxidation state of the diffusion layer of oxides at the interface with the titanium metal ,
which will attempt to grow in thickness at the baking temperatures due to oxidation of the titanium . I am thinking that some sort of extremely thin but effective
cold treatment of titanium should greatly benefit the adhesion and conductivity of the interface with whatever heavier baked layer of oxides goes on next , especially if the precurors for those subsequent oxides require significant heating before they begin to flux and diffuse
that very thin and cold applied primer layer . I can't find any reference to this sort of strategy being used , but it would seem to be a great experiment .

You maybe could simply wear some rubber gloves and use something like a carbide grit valve grinding compound made into a paste with the cobaltous acid , and use a swath of a scotchbrite scouring pad to physically scour and polish the titanium with it and see if any visible reaction occurs . It may be so thin as to not show visible coloration , but be glass clear .....even though it is formed there as an interface , and can only be detected by electronic means later . I have no idea on this ....but
it very well could behave similarly as does a cold bluing compound as used on gun metal , and be readily apparent
as a stain on the titanium .....or it may not be visibly apparent that an interface layer is there at all , even though it has formed .

Update

12AX7 - 17-9-2007 at 19:48

Fleaker sent me a teensy vial containing a smidgeon of potassium hexachloroplatinate, K2PtCl6.

Sooooo, I took a small fraction of the stuff and tossed it in about a hundred mls of water along with some muriatic acid, obtaining a weak yellow color identical to a similar strength chromate solution.

I took a strip of titanium and hit it with some negative volts, giving some hydrogen bubbles on it, and understandably, some chlorine gas from the graphite anode. Its appearance changed little. After torch annealing (during which I noticed redox behavior under the flame, identical to copper, where air oxidizes the layer into iridescent shades or the flame's radicals reduce it to metal), I had a silvery to iridescent yellow strip of titanium.

I took this piece and hooked it to some positive volts and immersed it in a solution of sodium chlorate (less than 10% Cl- I'm sure). The result, oxygen bubbles from the anode where the coating covered, and hydrogen bubbles at the cathode, in excess of the amount of oxygen (i.e. more than a factor of two). Probably there's a secondary reaction in there somewhere, and I'm betting it's perchlorate.

We'll see if it lasts the morning.

Tim

garage chemist - 17-9-2007 at 20:10

Is this treatment supposed to generate a coating of metallic platinum, or of platinum oxide?

I remember having read that electrolysis of aqueous platinum salt solutions with titanium cathodes is not suitable for making a platinized titanium anode. Platinized titanium anodes are made by electrolysing a Pt-containing salt melt with Ti cathode at a temperature of several hundred °C where the TiO2 layer is non-adherent.

12AX7 - 17-9-2007 at 20:45

Idunno. We'll see.

I guess it's a little bit of both metallic Pt and PtOx. N'maybe some TiOx for good measure. I couldn't guess how many microns, but probably not many. And who knows, there could even be Cu and Fe and Cr and Ni around. A lot of possibilities considering how little Pt is in the plating solution.

Edit: still bubbling, a few hours later. I said the anode is producing oxygen bubbles, which is probably true, but a smell test indicates ozone as well. The potential is definetly high!

Edit(2): still going today. Copper clip on the anode is substantially green; some titanium screws and busbar would be helpful here!

Tim

[Edited on 9-18-2007 by 12AX7]

[Edited on 9-18-2007 by 12AX7]

Fleaker - 24-9-2007 at 08:45

Why not try plating onto some nickel? Do you want me to send you some nickel as well? If you need more Pt, I could look for some chloroplatinic acid.

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