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More on PbO2 electrodes

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dann2 - 7-4-2007 at 10:41

Quote:
[QUOTE]


number is GB850380. Sorry for the confusion.

-Alembic


Hello,

The patent was very hard to find from the espace site for some reason or other. I found it eventually.
It is also published under:

US2872405 (A1)
FR1168150 (A)
DE1094245 (B1)

The patent mentions nothng about precoating the valve metal with Sn or Sb semiconductor oxides. I guess you added that in yourself.


It also mentions using Graphite to make Perchlorate. It says that it erodes too quick for commercial use.
It also says that Magnetite is only useful at low current densities.
Also Magnetite will make Perchloarate at a current efficiency of 4 to 5% according to the Patent.


Cheers,

Dann2

[Edited on 7-4-2007 by dann2]

Rosco Bodine - 7-4-2007 at 18:15

Quote:
Originally posted by dann2
Quote:
Originally posted by Rosco Bodine
This could be useful information , and I don't recall seeing it posted before . Evidently the co-plating of a controlled amount of bismuth peroxide with lead peroxide forms a
harder and denser , much more erosion resistant PbO2
anode which also operates at better current efficiency .
This is only useful in a limited thickness because cracking problems develop with heavier layers . It might be possible to build up a thicker anode using cloth wrap or intermediate layer reenforcement as was mentioned earlier in this thread .

The patent also describes an interesting improvised flow through coaxial electrode which was used for one of the experiments , where the electrolyte is pumped through
the electrode assembly .

[Edited on 5-4-2007 by Rosco Bodine]


Hello,

It is interesting to note that they only mention in the patent (page 6 lines 10 to 15) very brifely that it may be needed to coat the substrate with Pt or some of its oxides. You would think they were trying to hide the fact................

Cheers,

Dann2


Yeah , another little detail I saw mentioned in one patent is
that fluoride in the electrolyte is especially corrosive to
even a titanium substrate if it permeates through the
PbO2 ...which it is pretty much guaranteed to do sooner or later . This is one area where a graphite substrate may actually fare better ....plus the fact that it doesn't form a blocking diode junction to current flow when electrolyte does permeate through to the substrate .

The electrical connection can be made to the naked graphite on the unplated top section instead of having to clamp directly onto the PbO2 which is brittle .

Another little note I made was concerning the integrity of
the PbO2 plating , that besides iron being a contaminant to be avoided is also any organic materials on the substrate . So I would conclude that linseed oil would only be useful on
an already plated carbon , like dipping the unplated section .
That information about needing absolutely clean and degreased graphite for the substrate pretty much rules out any pretreatment of the graphite to make it hold up better .
The dense and impermeable structure of a high quality PbO2
plating is the most important factor in the longevity of
the anode ....no matter what substrate is used .

I expect that some of that thin wickable silicone cement as
is used for sealing windshield leaks could be useful on the
section where the PbO2 transitions to unplated graphite ,
sort of as a primer for heavier silicone glue used to secure
the electrode into a PVC or poly pipe fitting ....if a coaxial electrode was being made like they describe .

dann2 - 8-4-2007 at 04:57

Quote:
Originally posted by Rosco Bodine
Quote:
Originally posted by dann2


Hello,

It is interesting to note that they only mention in the patent (page 6 lines 10 to 15) very brifely that it may be needed to coat the substrate with Pt or some of its oxides. You would think they were trying to hide the fact................

Cheers,

Dann2


Yeah , another little detail I saw mentioned in one patent is
that fluoride in the electrolyte is especially corrosive to
even a titanium substrate if it permeates through the
PbO2 ...which it is pretty much guaranteed to do sooner or later . This is one area where a graphite substrate may actually fare better ....plus the fact that it doesn't form a blocking diode junction to current flow when electrolyte does permeate through to the substrate .

The electrical connection can be made to the naked graphite on the unplated top section instead of having to clamp directly onto the PbO2 which is brittle .

Another little note I made was concerning the integrity of
the PbO2 plating , that besides iron being a contaminant to be avoided is also any organic materials on the substrate . So I would conclude that linseed oil would only be useful on
an already plated carbon , like dipping the unplated section .
That information about needing absolutely clean and degreased graphite for the substrate pretty much rules out any pretreatment of the graphite to make it hold up better .
The dense and impermeable structure of a high quality PbO2
plating is the most important factor in the longevity of
the anode ....no matter what substrate is used.

quote]

Hello,

My understanding of the Ti Oxide build up between the Lead Dioxide and the Ti (or other valve metal) is that the oxide simply appears after some time even if no electrolite is getting through the PbO2 when the anode is being used in an electrolythic cell. This is why you need a Pt layer or some other sort of layer to stop the oxide from forming. The Pb02 simply does not 'agree' with the Ti (or other valve metal). Perhaps Alpha (plated from alkali PbO2 baths) Lead Dioxide is better at 'agreeing' with Ti (or other valve metal) that Beta Lead Dioxide (plated from Acidic Nitrate bath) as in many patents it is recommended that Alpha be plated first. Then again usually the patents recommending Alpha are coming from a point of view of releaving stress in the Lead Dioxide.

All commercial valve metal substrate Lead Dioxide anodes have a Pt coat (probably very thin) of some description on the valve metal first. I read this somewhere, can't remember where.

I totally agree with the fact that you need a good coating of Lead Dioxide to protect the substrates. The idea behind the plastic, ceramic, substrates is that 'any old coating' of lead dioxide would do. This is not the case. You still need a good coating to carry heavy current etc.



Cheers,

Dann2

Alembic - 8-4-2007 at 16:27

Quote:


Hello,

My understanding of the Ti Oxide build up between the Lead Dioxide and the Ti (or other valve metal) is that the oxide simply appears after some time even if no electrolite is getting through the PbO2 when the anode is being used in an electrolythic cell. This is why you need a Pt layer or some other sort of layer to stop the oxide from forming. The Pb02 simply does not 'agree' with the Ti (or other valve metal). Perhaps Alpha (plated from alkali PbO2 baths) Lead Dioxide is better at 'agreeing' with Ti (or other valve metal) that Beta Lead Dioxide (plated from Acidic Nitrate bath) as in many patents it is recommended that Alpha be plated first. Then again usually the patents recommending Alpha are coming from a point of view of releaving stress in the Lead Dioxide.

All commercial valve metal substrate Lead Dioxide anodes have a Pt coat (probably very thin) of some description on the valve metal first. I read this somewhere, can't remember where.

I totally agree with the fact that you need a good coating of Lead Dioxide to protect the substrates. The idea behind the plastic, ceramic, substrates is that 'any old coating' of lead dioxide would do. This is not the case. You still need a good coating to carry heavy current etc.



Cheers,

Dann2


You're right, about the PbO2 not agreeing with the Ti. The problem is quite simply the fact that PbO2 (whether Alpha or Beta) is a very strong oxidizing agent and Ti is actually pretty easily oxidized (at least until a sufficiently thick layer of TiO2 is formed). A layer of PbO2 plated directly onto Ti is inherently unstable, at least thermodynamically.

SnO2 is resistant to most acids and when appropriately doped electrically conductive. It is also not much of an oxidizing agent, which is why it works well when used as a buffer layer between PbO2 and Ti.

-Alembic

hashashan - 9-4-2007 at 06:53

Anyopne tried to use Tin as a subtrace or a contact?
Mybe as an electrode ... IIRC it is pretty resistant ... might be wrong

little success making PbO2 electrode

quest - 9-4-2007 at 11:06

Hi guys, I tried in the past few weeks making a good PbO2 electrode for perchlorate.
I think I succeeded making an usable electrode.
I used CD cut to squere as a base, wet it with MEK and powdered it with PbO2 powder.
After this I connected it to a graphite electrode and for 48H I coated it - at first with minimal current and in the last 4 hours with about 0.05A/cm^2.

This is the result:




I think I will try to convert NaChlorate to NaPerchlorate in the coming month.

hashashan - 9-4-2007 at 12:33

Nice man looks a lot like my first electrode(and thats not good news ;) )... try using scotch... i also tried to make a plastic subtrace.. my problem was that for some reason the electrode just cracked and fell off the plastic.
Also there is quite a problem with the connection, you do need silver paint. I ordered some so when ill recieve it i can give you some of it. If youll use just a metal youll get a lot of resistanse on the contact thus low potential on the anode and then no perchlorate .. thats what happned in my experiment.
Soon ill try to make a proper electrode with scotch and silver paint. :cool:

dann2 - 9-4-2007 at 17:07

Quote:
Originally posted by hashashan
Nice man looks a lot like my first electrode(and thats not good news ;) )... try using scotch... i also tried to make a plastic subtrace.. my problem was that for some reason the electrode just cracked and fell off the plastic.
Also there is quite a problem with the connection, you do need silver paint. I ordered some so when ill recieve it i can give you some of it. If youll use just a metal youll get a lot of resistanse on the contact thus low potential on the anode and then no perchlorate .. thats what happned in my experiment.
Soon ill try to make a proper electrode with scotch and silver paint. :cool:


Hello,

The problem with the bad contact is that heat will be generated in the contact area which may damage the anode.
It will waste electical power too but we dont worry too much about power wastage.
The voltage dropped will NOT stop Perchlorate (or Chlorate) from forming so long as you have a sensible current density on the Anode.

Dann2

[Edited on 10-4-2007 by dann2]

dann2 - 9-4-2007 at 17:15

Quote:
Originally posted by hashashan
Anyopne tried to use Tin as a subtrace or a contact?
Mybe as an electrode ... IIRC it is pretty resistant ... might be wrong


Never heard if being used anywhere. It is easily (IMHO) attacked by the (Per)Chlorate electrolite. You will need a perfect coating of Lead Dioxide. It will also be attacked by the Nitric Acid in the plating tank. You will have to plate it from a neutual (or close to neutral) plating tank or use a alkali plating tank (Lead Tartarate bath) You might as well use graphite, or Iron or Nickle.
The whole idea of the inert (plastic/cloth/ceramic or whatever) substrate is taht a poor coating of Lead Dioxide willl give a workable anode.
This has proved not to be the case (alas) as you still need a fearly good coat of Lead Dioxide for to carry heavy currents when anode goes into (Per)Chlorate cell.

Cheers,

Dann2

dann2 - 9-4-2007 at 17:29

Quote:
Originally posted by Alembic




You're right, about the PbO2 not agreeing with the Ti. The problem is quite simply the fact that PbO2 (whether Alpha or Beta) is a very strong oxidizing agent and Ti is actually pretty easily oxidized (at least until a sufficiently thick layer of TiO2 is formed). A layer of PbO2 plated directly onto Ti is inherently unstable, at least thermodynamically.

SnO2 is resistant to most acids and when appropriately doped electrically conductive. It is also not much of an oxidizing agent, which is why it works well when used as a buffer layer between PbO2 and Ti.

-Alembic


Hello Alembic,

That is the explanation I never had before. Was probably told before though!

Way way way back in the year 1999 :D I used to think that Ti
was too exotic as a substrate and was determined to stay away from it. In the mean time ebay etc has come along and Ti is now readily available. Think it's time I moved with the times.
Are there any other coatings between the valve metal and Lead Dioxide that may work that you are aware off.



Cheers,

Dann2

hashashan - 10-4-2007 at 01:32

dann, my problem with the cell was that I had a lot of resistance in the contact and thus very low potential at the anode. I didnt use NaF and so instead of the chlorate that was formed from the NaCl converted to tht perch it was converted to the NaOCl and even after very extended periods of time no perch or even sensible amounts of chlorate were formed.
Now i am running a chlorate cell and then ill use pure chlorate and a good anode with silver conection to convert it to perch

Alembic - 11-4-2007 at 11:35

Quote:
Originally posted by dann2

Hello Alembic,

That is the explanation I never had before. Was probably told before though!

Way way way back in the year 1999 :D I used to think that Ti
was too exotic as a substrate and was determined to stay away from it. In the mean time ebay etc has come along and Ti is now readily available. Think it's time I moved with the times.
Are there any other coatings between the valve metal and Lead Dioxide that may work that you are aware off. I will post the patent number as soon as I manage to find it again.

-Alembic



Cheers,

Dann2


I also used to feel that Ti was too exotic and expensive, till I just got so tired of my ceramic and graphite substrate anodes cracking or failing otherwise. The resulting amount of toxic waste was also getting a bit embarrassing:D

There are other interlayers that can be used such as Pt for TiO2/Ta2O5 just to mention two examples.

I chose the SnO2/Sb2O3 system because it is easy to apply and the raw materials are easy to come by and above all cheap. SnO2 also has a higher oxygen overvoltage than PbO2 which supposedly means that any exposed SnO2 will not interfere with the anodic formation of perchlorate.

-Alembic

SAM4CH - 15-4-2007 at 12:45

In chlorate cell using graphite anodes, when I use sodium dichromate and tried to ppt. dichromate as barium dichromate using 10% excess BaCl2 and tried to ppt. excess with NaCO3 but my solution still pale yellow!! how can I get colorless electrolyte "full procedure" ??

12AX7 - 15-4-2007 at 14:29

Why do you need to precipitate it?

Clearly, barium (di)chromate is quite soluble! Did you check the ionic strength, by any chance? It doesn't take much chromate to look yellow, either.

My electrolyte is all green at the moment. More curious to me is, why is it even dissolved? Cr(OH)3 should be precipitated; I don't think the pH is so high (I'm not adjusting it any, mind you) that Cr(OH)4 is present.

Tim

P.S. To mods: split these two posts into the KClO3 thread. This has nothing to do with PbO2.

dann2 - 15-4-2007 at 18:44

Quote:
Originally posted by SAM4CH
In chlorate cell using graphite anodes, when I use sodium dichromate and tried to ppt. dichromate as barium dichromate using 10% excess BaCl2 and tried to ppt. excess with NaCO3 but my solution still pale yellow!! how can I get colorless electrolyte "full procedure" ??


Hello,

I shall quote Garage Chemist from the thread 'Thoughts on Anodes'.

I destroy residual chlorate by acidifying the solution, adding sodium disulfite and boiling. The solution must give off SO2, otherwise more disulfite must be added. A SO2 smell from the solution is the sign that all chlorate has been reduced.
This also reduces the added dichromate to trivalent chromium, which is then precipitated as the hydroxide by adding NaOH solution and filtering.

The above was in relation to a Perchlorate cell btw.
Hope this helps.

As for the green colour in a Chlorate cell. Is there any Copper about?
Are you still using the bucket with the Carbon suspended on Copper pipes?

Cheers,
Dann2

12AX7 - 15-4-2007 at 19:27

Nope, haven't had copper in it in some time. The only green thing, besides the possibility of chromium, is the mild steel plate bottom of the cell. I keep voltage on the cell pretty much at all times (including when boiling to decompose hypochlorite, but not when pouring out the liquor), so that's a low priority, and would most likely appear light purple (FeO4) anyway.

Green would be consistent with copper in a strong chloride solution, but not with the pH, which is soapy to my fingers after a minute of contact (maybe...pH 9?).

I am reusing the salt (which had since dried completely) from previous runs, so if the contaminant remained soluble, it could possibly be residual.

Tim

SAM4CH - 16-4-2007 at 13:44

I add NaOH for my solution to reach pH=8-9 and added barium chloride 10%excess "my dichromate conc. 2g/L" there was ppt and filtered but filtrated solution still has yellow color!!? what is the problems here

12AX7 - 16-4-2007 at 14:52

What is the solubility of BaCrO4 anyway? Ksp = 2.2 x 10^-10, so with nothing else in solution, you'll have roughly 20uM of each. Maybe 10uM CrO4(2-) let's say. That's still in the ppm range, which is quite visible. Spectrophotometric limits on chromate go into the ppb range.

You might try lead instead (about 28 times less soluble). Mind the PbCl2 or PbSO4 precipitate when in excess.

Tim

dann2 - 16-4-2007 at 15:28

Quote:
Originally posted by SAM4CH
I add NaOH for my solution to reach pH=8-9 and added barium chloride 10%excess "my dichromate conc. 2g/L" there was ppt and filtered but filtrated solution still has yellow color!!? what is the problems here


I once had a conversation with guys about a persistent yellow colour in their Chlorate solutions. Someone suggested it may be collidal Iron.

Dann2

SAM4CH - 17-4-2007 at 02:17

Ok.. not colloidal iron because I prepare fresh solution from 2g/L dichromate in 1L distilled water without electrolysis but the yellow color remains:(

I added before minutes very excess of BaCl2 "around 10-30 times of required in balanced equation" and I get very clear solution !!!???

[Edited on by SAM4CH]

hashashan - 22-4-2007 at 01:46

Great resultd.
Ive tested out my cloth reinforced anode with the silver paint and results are good :) made about 100rams of perch from chlorate.
Now a question:
I converted it to K-perch, how can i destroy the chlorate? the sulfite solution will still work?
how much sulfite should i add? is there a cheaper method? can i convert this perch to AP after i destroy the chlorate without the fear of all the thing going off, i dont have any indicators to check for chlorate traces.

12AX7 - 22-4-2007 at 07:32

No, potassium perchlorate is much less soluble than ammonium perchlorate.

Use a reducing agent such as Fe(II), sulfite, etc., and acid if necessary to get it going. The KClO4 will remain undissolved (keep it cool to minimize loss).

Tim

hashashan - 22-4-2007 at 08:40

destroyed the chlorate with excess of HCl,
after the filtering and wash it doesnt react with conc. H2SO4 and doesnt color HCl in yellow is it a good enough indicator? i just dont have anythin better

Rosco Bodine - 22-4-2007 at 20:39

Quote:
Originally posted by dann2
Silver is the best by far connection to Lead Dioxide as this article describes.

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



Silver is actually the best physical contact surface even more generally , particularly for any gently clamped connection , because when it oxidizes , the oxide itself has good conductivity . So even if you are clamping onto graphite for example , and even where some wicking or moisture corrosion is inevitable , silver should fare better than copper .

Thin silver sheet can be soldered onto a copper backing for economy and used to line the jaws of spring clamps or
used in fabricating connection terminals for anodes .
Silver sheet can be hard to find . Here is one source which
seems fairly reasonable in pricing , and supplies useful thicknesses .

Spot silver price on unfabricated forms is presently about $14.00 troy oz. just for reference .

http://www.silversupplies.com/catalog/metals/fine_silver/she...

[Edited on 22-4-2007 by Rosco Bodine]

hashashan - 26-4-2007 at 00:34

As promised, a photo of my cloth reinforced anode.

and a close up, looks like a volcano rock :D

FrankRizzo - 26-4-2007 at 13:05

Damn, that looks like one my roommate's socks :)

Great job, btw.

hashashan - 26-4-2007 at 16:47

well actually the cloth is from a sock ... so there is a chance there ... :)

dann2 - 28-4-2007 at 07:22

Quote:
Originally posted by hashashan
well actually the cloth is from a sock ... so there is a chance there ... :)


What material is the sock made out off?

Cheers,

Dann2

hashashan - 28-4-2007 at 13:14

just a simple thick sock .. it was made out of some kind of cloth
however some bad news, my contact disintegrated.. heated up and a part of the electrode caught fire and burned out. so i think ill try to make a plastic anode from a CD

hashashan - 29-4-2007 at 10:17

Hey guys, i am having troubles using this silver paint. can i just use a silver wire instead?
i mean just clip on a silver/silver plated wire?

12AX7 - 29-4-2007 at 19:17

I use a copper strap and spring clamp for electrical connection to my bar of graphite. It gets a little crusty, but mostly from salt. It's far above the solution, out of the spray and gas for the most part. You need a tall, sturdy electrode for this.

Copper plating may also be a possibility if you don't have silver. The other day I made a suprisingly adherent layer of copper on a spare piece of graphite, from a strong copper and HCl solution (that may have Ni or Fe in it also).

Tim

hashashan - 29-4-2007 at 22:38

but i have a cloth reinforced PbO2 anode.... what does graphite has to do with it. i once tried to clamp graphite on it but had way to much resistance.
well i bought a silver wire today, hopefully it will do the trick

12AX7 - 30-4-2007 at 00:48

C and PbO2 are both ceramics. A clamp works for my ceramic. Maybe it will work for yours? :P

Tim

hashashan - 30-4-2007 at 00:54

what clamp?
the problem with PbO2 is that it is a powerfull oxidiser and will oxidise most metals in the point it touches them. Silver has a conductive oxide, thats the trick :)
the problem with bad connection is huge resistance wich leads to low potential (no perchlorate, and even no chlorate) and high temperature wich can and does lead to autoignition of the anode.

12AX7 - 30-4-2007 at 07:25

I know! Cut a hole in the bottom of a plastic jar, silicone it over the top of the electrode and fill with... MERCURY! :D

Woulda passed in the 19th century, anyways...

Hmm, what kind of heat can that thing ultimately handle, anyway? Fusable metal might be a solution after all...

Silver plating would be nice though, yeah.

Tim

hashashan - 30-4-2007 at 07:31

I dont how much heat can it handle, but the bad thing is that its a kinda shitty heat conductor. While i was electrolizing the solution was 50 degrees while the part of the electrode that was over the liquid was on flame :D

silver plating is problematic there.
A new direction i was thinking of is Tantalum, its quite cheap on ebay. anyone had luck in plating tantalum? maybe a partial coating? i mean cloth reinforced tantalum tipped (coated also with the same layer of PbO2) anode?

dann2 - 30-4-2007 at 09:07

Quote:
Originally posted by hashashan
I dont how much heat can it handle, but the bad thing is that its a kinda shitty heat conductor. While i was electrolizing the solution was 50 degrees while the part of the electrode that was over the liquid was on flame :D

silver plating is problematic there.
A new direction i was thinking of is Tantalum, its quite cheap on ebay. anyone had luck in plating tantalum? maybe a partial coating? i mean cloth reinforced tantalum tipped (coated also with the same layer of PbO2) anode?


It would be cheaper to use Titanium. Tantalum can be difficult to come by in a shape(flat sheet) that you want.
All valve metals will require a precoat of something that will protect them from the Lead Dioxide. You will need Pt, or Pt Oxide or doped Tin Oxide.
One patent I have seen plated Lead Metal onto Ti then formed a coat of Alpha Lead Dioxide on the Lead by electrolysing in sulphuric acid. Then plating on top with Beta Lead Dioxide (Lead Nitrate bath)

What sort of currents are you putting into your anode. If anode surface at contact is very rough try using graphite paste.

Dann2

hashashan - 30-4-2007 at 09:14

i put about 12 amps. the process started like a charm and then something happned .. the contact got crappy and thats it.
nobody answered me, what will happen if ill just use a silver wire, i got a pretty thick one. about 1 mm.

hashashan - 30-4-2007 at 13:49

the silver wire doesnt seem to work, neither graphite. What on earth could be the reason? i tried to connect it to a million places, the anode just started to be a crappy conductor. Any suggestions?

12AX7 - 30-4-2007 at 17:38

You need more contact area. Grind down a smooth spot on the electrode and use sheet stock.

Tim

hashashan - 30-4-2007 at 23:11

i tried it all, it just wont conduct ... very weird

hashashan - 1-5-2007 at 12:02

And another question,
Did anyone ever tried to grow a massive anode on a piece of Pt?
I am about to receive a piece of Pt, And i thought to grow the anode on it and slowly take it out and grow more, i mean to take it out mm by mm while the last mm grows again,
Actually i want to grow a 30sq.cm anode on 2cm pt wire, possible?

Twospoons - 1-5-2007 at 13:50

I have to ask the obvious question: have you checked the rest of your power supply? Could the conduction break be somewhere else?

dann2 - 1-5-2007 at 14:43

Quote:
Originally posted by hashashan
And another question,
Did anyone ever tried to grow a massive anode on a piece of Pt?
I am about to receive a piece of Pt, And i thought to grow the anode on it and slowly take it out and grow more, i mean to take it out mm by mm while the last mm grows again,
Actually i want to grow a 30sq.cm anode on 2cm pt wire, possible?



If you are going to get into the business of growing massive Lead Dioxide anode (like growing an anode by starting with 2 cm of Pt.) you will need a well contolled set up. Good pH control, fearly steady Lead Ion concentration, steady temp. etc etc. Lead Dioxide can be deposited on Pt. It has been done many times when Ti was plated with Lead Dioxide. A thin coating of Pt was deposited first to protect the Ti from the Lead Dioxide.
I was flicking through a library book today and read that Lead Dioxide was known as the 'Poor man's Platinum'. HUH.

You can grow massive anodeS on Iron, Nickle and other wires. It has been done in the journals. The maker started with a close to neutral Lead Nitrate bath and kept plating solution treated with Lead Carbonate etc to neutralize the nitric acid as it was produced to stop it from attacking the Iron, Nickle etc. Well controlled set up.
Can I presume that the plating tank for the 'Sock substrate anode' was a simple affair. This type of set-up will surely let you down if you try to make massive anodes.

What are you replacing the Lead in the tank with as it gets depleated?




DANN2

dann2 - 1-5-2007 at 15:32

Quote:
Originally posted by Alembic

I have had some success with PbO2 Ti anodes. (Do a search for my old posts if you would like to see a picture). I have tried *many* substrates before that (carbon from batteries, pure graphite as well as ceramic) in the distant past but came to the conclusion that Ti is the most suitable.

BTW, the dimensions of the anode in the picture are 5cm x 30cm.

The process that I finally settled upon is a bit laborious but I have had pretty consistent results:

I used Ti sheet of about 1mm thickness because that is waht I had at the time. A little thicker would probably be better.



Next, a semiconducting coat of Sb doped SnO2 was applied by painting on a solution of SnCl4 + SbCl3 in water + butanol, drying, and then heating to 500 degrees Celsius or so in an oxidizing atmosphere i.e. air. This step was repeated five to ten times to give a suitable coating thickness. I will try to find the patent that describes this.

Then a thin (about 0.1mm) layer of alpha PbO2 was plated onto the substrate from a alkaline lead tartrate bath. See pat. GB 850,830 for info.

The final coat of beta PbO2 was then plated over top of this from a lead nitrate bath, also described in GG 850,830
This layer was about 2mm thick.

The anode performed well in a perchlorate cell.

-Alembic


Hello Alembic,

What grade of Ti did you use. Would it be a problem if pure Ti was not used.

Cheers,
Dann2

hashashan - 1-5-2007 at 22:45

actually i didnt. It was a one time setup.
I dont have any lead carbonate. however i thought that maybe the lead carbonate may be replaced with Copper carbonate as the copper also gets depleted. and i didnt think to coat anythin with Pt but just to use Pt and thats it.
also a nice ide i got was to combine the Pt with the cloth anode. I mean make a permanenet contact even befor the anode is ready bu clamping a
Pt wire and start to plate with it partially submerged, that way i dont have to take care of the solution too much right?
Here is the procedd i thought of:
rub in the paste into a cloth. insert the Pt piece ... clamp it. submerge the whole cloth and half of the Pt wire and start to plate at low curents untill we get a decent coating.

Another problem i had is that the second i submerged my rubbed in anode or even plastic with sprinkled PbO2 , all the PbO2 dissolved immediately, what can that be? too much acid in the tank? or any other reason?

dann2 - 2-5-2007 at 17:40

Quote:
Originally posted by hashashan
actually i didnt. It was a one time setup.
I dont have any lead carbonate. however i thought that maybe the lead carbonate may be replaced with Copper carbonate as the copper also gets depleted. and i didnt think to coat anythin with Pt but just to use Pt and thats it.
also a nice ide i got was to combine the Pt with the cloth anode. I mean make a permanenet contact even befor the anode is ready bu clamping a
Pt wire and start to plate with it partially submerged, that way i dont have to take care of the solution too much right?
Here is the procedd i thought of:
rub in the paste into a cloth. insert the Pt piece ... clamp it. submerge the whole cloth and half of the Pt wire and start to plate at low curents untill we get a decent coating.

Another problem i had is that the second i submerged my rubbed in anode or even plastic with sprinkled PbO2 , all the PbO2 dissolved immediately, what can that be? too much acid in the tank? or any other reason?


Only a littel Copper gets depleated because only a little gets deposited onto the Cathode. If there is a good blue colour there is probably enough Copper.
The Lead (or Lead ion to be more exact) gets depleated because it is being deposited on the Anode in the form of PbO2. As PbO2 gets deposited nitric acid forms in the solution. When you add Lead Carbonate (or Hydroxide, or Basic Carbonate or Litharge) it neutralizes the acid and increased the Lead Ion concentration.
I have noticed that if you try to plate with too low of a Lead ion concentration the PbO2 will be stripped from the Anode.

You could make a good connection to PbO2 with Platinum I would think IF the Pt is large enough to carry the current that your anode will be working with. A one mm diameter wire will not carry a very big current.

I read in alot of patents that the Lead Nitrate concentration should be at least 200 grams per liter. I have seen patents that use up to 800 grams per liter.

DANN2

hashashan - 3-5-2007 at 13:38

So any reasons i didnt manage to plate the anode?
the solution was pretty saturated, some crystals were even crystalizing out.
and why do you think that a short 1mm wire wont carry about 15 amps?

dann2 - 3-5-2007 at 17:12

Quote:
Originally posted by hashashan
So any reasons i didnt manage to plate the anode?
the solution was pretty saturated, some crystals were even crystalizing out.
and why do you think that a short 1mm wire wont carry about 15 amps?


Hello,

How much is pretty saturated?
How many grams of Lead Nitrate per liter were you using when you started to plated the anode.
Was the plating tank big enough so that the Lead Ion concentration did not get too low before the anode was finished plating.
Lead Nitrate solubility gets less and less as the Nitric acid concentration goes up and up. If you keep adding Lead Nitrate to the tank to replace the Lead Ions that have been used up, there will come a point where the Lead Nitrate will start to crystallize out on the anode. The Nitric acid concentration will be at a max. along the plating anode. You need to keep the Lead Ion replenished using a Lead compound that also neutralizes the acid.

1MM dia. Pt wire is thick enough to carry 15 amps. It would be near the absolute maximum I would ask it to carry. It may heat up too much.

Dann2

hashashan - 4-5-2007 at 02:47

the solution was neutral and some lead nitrate started to crystallize out, that why i say it was saturated.
the problem was that i mixed it with another solution that was pretty acidic (found out after the addition) it was about PH 1-2 maybe that was the reason that all the PbO2 that was sprinkled on the plastic and fabric was dissolved? or there might be another reason?

dann2 - 4-5-2007 at 14:59

Quote:
Originally posted by hashashan
the solution was neutral and some lead nitrate started to crystallize out, that why i say it was saturated.
the problem was that i mixed it with another solution that was pretty acidic (found out after the addition) it was about PH 1-2 maybe that was the reason that all the PbO2 that was sprinkled on the plastic and fabric was dissolved? or there might be another reason?


Perhaps you bath is contaminated with something. Some of the patents give contaminates that were bad news. Chloride was one of them. Iron also.

If you can get a small piece of graphite (not a gouging rod) and see if it will plate ok.
Are you using high grade chemicals to make up the bath or is the Lead Nitrate (and carbonates, or hydroxides or litharge) homemade.
What type of water are you using, tap or distilled. You may have contaminates in the water.
I used to test my tank using a piece of graphite to see if it would plate ok before I tried a more 'exotic' substrate. If it will not plate graphite, and the Lead Ion and Nitric acid concentrations are within acceptable limits then the bath must be contaminated with something.
What temperature are you using. If the temperature is too low I would think the bath will not plate properly.

Dann2

hashashan - 5-5-2007 at 02:27

well ill try to maintain better conditions.
just that i used that solution already to make an anode, only added more nitrate to it thats it.
well ill do my best again
thanks

Rosco Bodine - 9-5-2007 at 11:41

Just offering a thought concerning pH control and lead content replenishment in the electrolyte from which PbO2 is being plated .

Lead forms basic salts which are less than half the solubility of the normal salts in plain water , and likely
even less soluble in solutions already concentrated
with respect to the normal salt .

It would seem there are a couple of ways that this could be exploited , depending upon the accuracy demanded for
the particular plating process . It may be adequate to
simply bundle some of the basic nitrate in a piece of cloth
gathered into a ball , and use it like a teabag in the
electrolyte . There should be a solubility equilibrium where
the presence of the solid undissolved basic salt in contact with a solution of the normal salt would function as a buffer to automatically maintain the composition of the electrloyte constant , with regards to both pH and concentration of Pb ion . As the electrlolyte became more
acid because of lead plating out , the acidity would react
with the basic salt converting it to the normal salt which would enter solution to maintain the equilibrium .

A mechanically controlled method could be used also to
maintain the equilibrium or any desired composition at any point away from equilibrium .
A heating tape could be used to keep a graduated addition funnel warm so that a relatively saturated solution of the basic salt could be kept available for metered dropwise addition at a rate calculated to match the lead deposition rate as a function of current efficiency , and measured current . This would
be a relatively precise method also .

There are a series of basic salts associated with the acetate , one or all of which could be useful if acetate
is tolerable or desired in the particular plating bath .
And there is one basic nitrate of lead which should also
be workable in either of the schemes for keeping the
electrolyte composition constant . IMO these methods
could have advantages over the use of carbonate ,
primarily that no microbubbles of CO2 would be introduced into the solution as a byproduct which could
roughen the surface plating , and that the handling
of soluble basic salts is otherwise more convenient for
metering precisely during additions , than is the manipulation involving additions of a solid carbonate ....
which just seems to be a poorer source of lead ion to
be added to a sensitive reaction system .

[Edited on 9-5-2007 by Rosco Bodine]

hashashan - 9-5-2007 at 13:36

Guys anyone tried to make perch from NaCl directly with PbO2? its the second time i get crappy results.
What happens when i electrolyze above 6V, i do it @ 12V 10A with anode surface about 40cm^2. when i did this from chlorate everything went swiftly, but from NaCl when i try to make a probe crystallization with KCl all i get is a white cloudy substance and not even the chlorate crystals, any thoughts on that?

12AX7 - 9-5-2007 at 16:29

KClO4 is rather insoluble and would tend to make a flocculent precipitate, especially if the KCl is concentrated. The only other possiblity is PbCl2, but that would require the solution to be initially acidic and reducing (something which would dissolve the PbO2).

Filter and recrystallize.

Tim

dann2 - 9-5-2007 at 18:07

Quote:
Originally posted by hashashan
Guys anyone tried to make perch from NaCl directly with PbO2? its the second time i get crappy results.
What happens when i electrolyze above 6V, i do it @ 12V 10A with anode surface about 40cm^2. when i did this from chlorate everything went swiftly, but from NaCl when i try to make a probe crystallization with KCl all i get is a white cloudy substance and not even the chlorate crystals, any thoughts on that?


Hello,

How many grams Chloride was in the cell at start?
How many ml's solution did you have?
How many amper hours did you run into the cell?

It is not the voltage that you are applying to the cell that
gives the conditions for Perchlorate formation.

If you get an immediate cloudy ppt with KCl then that is Perchlorate precipitating. The KCl is a relatively crude test.

Cheers,

Dann2

hashashan - 9-5-2007 at 23:10

Well i didnt wait enough for the crystalisation, i do have some chlorate but still no perchlorte(which is ok).
I am running a cell :
Volume : 1 liter
NaCl : 350gr
Amps : 10
AH : about 1000

However the cloudy ppt isnt perch, it remained even after i boiled the solution with sulfite in order to check for perchlorate. its some kind of a fluffy cloudy ppt, looks alot like the residue of a very concentrated KOH solution upon cooling.

dann2 - 10-5-2007 at 17:58

Quote:
Originally posted by hashashan
Well i didnt wait enough for the crystalisation, i do have some chlorate but still no perchlorte(which is ok).
I am running a cell :
Volume : 1 liter
NaCl : 350gr
Amps : 10
AH : about 1000

However the cloudy ppt isnt perch, it remained even after i boiled the solution with sulfite in order to check for perchlorate. its some kind of a fluffy cloudy ppt, looks alot like the residue of a very concentrated KOH solution upon cooling.


I calculate the 'run time' of the cell to be about 5.7 days.
This 'run time' assums the cell is finished when concentration of Chloride is at 100 grams per liter. To get Perchlorate to start to form you would need to run for at least 6 days on top of this (guessing).
I am using the program at the bottom of this page to calculate the time to get to 100grams/liter.


edit: to get down to 100g/l chloride

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

What sort of cathodes are you using

Cheers,
DANN2

[Edited on 12-5-2007 by dann2]

dann2 - 12-5-2007 at 07:14

Hello,

I was redissolving some Na Chlorate (contained some Chloride, no Perchlorate) after one crystallization from
cell liquid and when I added water I too got a ppt
floating about in the water that will not dissolve.
Heating makes no difference.
Adding acid
makes it dissapear as I tried it on a small quantity.
I do not know what the PPT is.

Dann2

dann2 - 13-5-2007 at 05:59

Quote:
Originally posted by dann2
Hello,

I was redissolving some Na Chlorate (contained some Chloride, no Perchlorate) after one crystallization from
cell liquid and when I added water I too got a ppt
floating about in the water that will not dissolve.
Heating makes no difference.
Adding acid
makes it dissapear as I tried it on a small quantity.
I do not know what the PPT is.

Dann2


After boiling the above solution and concentrating, the PPT appeared to turn a brown colour. Then it dissapeared on cooling. I thing the Chorate, as it crystallized, removed the ppt from the solution. It is physically incorporated into the Chlorate crystals (this is just a guess)

Is boiling Chlorate solutions compatable with borosilicate glass.

For examply, boiling NaOH solution is not, would the Chlorate be attacking the glass?
(or is it just Lead making me paranoid)

Dann2

12AX7 - 13-5-2007 at 11:54

Hell, chlorate is compatible with iron, I've boiled solution in tin cans many times. Hypochlorite is nasty on steel, but chlorate is fine.

Tim

hashashan - 13-5-2007 at 13:09

Quote:
Originally posted by dann2
Quote:
Originally posted by hashashan
Well i didnt wait enough for the crystalisation, i do have some chlorate but still no perchlorte(which is ok).
I am running a cell :
Volume : 1 liter
NaCl : 350gr
Amps : 10
AH : about 1000

However the cloudy ppt isnt perch, it remained even after i boiled the solution with sulfite in order to check for perchlorate. its some kind of a fluffy cloudy ppt, looks alot like the residue of a very concentrated KOH solution upon cooling.


I calculate the 'run time' of the cell to be about 5.7 days.
This 'run time' assums the cell is finished when concentration of Chloride is at 100 grams per liter. To get Perchlorate to start to form you would need to run for at least 6 days on top of this (guessing).
I am using the program at the bottom of this page to calculate the time to get to 100grams/liter.


edit: to get down to 100g/l chloride

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

What sort of cathodes are you using

Cheers,
DANN2

[Edited on 12-5-2007 by dann2]

when you say 6 days on top of that what exactly do you mean? on top of the 5 days or just 6 days?
the cathode is a gauging rod, i have put there several but decided to use only one (the distance between the anode and cathode is about 8cm) because when i used more then one the current was way to high.

an idea similar to the cloth reenforced GSLD

Rosco Bodine - 13-5-2007 at 14:00

On page 7 of this thread a patent US4236978 was posted by me , in connection with an idea of spiral wrapping a
graphite substrate with stator lacing tape , which I thought
might produce a similar effect as described in the patent .

I have been thinking some more about this and have another
related idea , which involves actually cutting a thread on the
graphite rod , and then wrapping a spiral of polyester filter
yarn directly into the grooves of the thread . Possibly a second spiral wind of yarn could be laid down in the same
direction , between the windings of the first spiral , to completely cover the peaks of the threaded graphite .
But such a second spiral may not even be necesssary .
The polyester filter yarn could be wound at a controlled tension using the same technique as used for winding wire
on a magnet coil , the precision drag on a Penn deep sea
fishing reel at a minimal setting , if you have one would work great for this .

Anyway , if the claims of the patent are accurate , then having a suitable polyester substrate at the interface between graphite and lead dioxide which is being plated ,
greatly reduces the complexity of the electrolyte required for
producing a superior anode , and widens the window considerably for the conditions that are needed for producing
a high quality PbO2 anode .....so the plating process is more forgiving of an improvised setup , where more exotic electrolyte mixtures and close control of the process is
difficult or impossible .

Many of the patents concerning various improvements move things towards greater complexity , using extra steps and
electrolyte additive ingredients , and carefully controlled conditions to achieve better results , but US4236978 seems
to be the only one which *simplifies* things for a GSLD type
of anode .

I don't know if the spiral wrapped polyester filter yarn will
work , but it is OTC in water filter cartridges and it seems worth a try as a winding . I am not sure if the brittleness
of a gouging rod , or a high density graphite rod will permit
threading to be cut using an ordinary threading die . An
Acme thread with a very progressive and gently tapered cut
in a deeper die , something like a coupling sleeve nut which has been reamed , throated , and slotted down its length in the middle of a flat might have to be made if the graphite is too brittle for a standard threading die .

IIRC , I have used a brass nut as a connection for the top of round graphite rods , by cutting a couple of internal slots
lengthwise across the threads in the nut using a needle file ,
and then hand threading the nut which was made into an
improvised thread cutting die , onto the graphite rod and
then soldering a ring terminal to it . But that would have been thirty years ago , so I can't swear to it .

Eclectic - 13-5-2007 at 14:29

It would be much simpler to cut large external threads in graphite in a lathe. I might give it a try, but I like the SnSb oxide on titanium better. I think there will always be a problem with the PbO2 oxidizing the graphite surface and causing high resistance over time.

Dip and bake SnSbO2 on graphite first? Should be easy to test with 95/5 solder dissolved in HCl/peroxide solution.

dann2 - 13-5-2007 at 15:46

Quote:
Originally posted by hashashan

when you say 6 days on top of that what exactly do you mean? on top of the 5 days or just 6 days?
the cathode is a gauging rod, i have put there several but decided to use only one (the distance between the anode and cathode is about 8cm) because when i used more then one the current was way to high.


I meant that you will need to run for another 6 days after you have run the cell for 5 days. (11 days total). The 6 days are a guess because it is very hard to know when the Chloride concentration will get down to (about) 10% and Perchlorate will start to form.
In fact the 5 days is a guess too because we are guessing the current efficiency to be about 50%.
A guy told me (on the blog of the geocities page) that he was able to purchase Methylene blue in a pet shop. It is useful to have for testing for Perchlorate.
It is for sale on ebay too.

Cheers,

Dann2

Rosco Bodine - 13-5-2007 at 15:48

@Eclectic

Often I have wondered if there is an electrical differential
across the interface between the graphite and the PbO2
which is aggravated when the contact is made to the graphite alone , when the anode is in service in the perchlorate cell . It may increase the service life of the anode to make the connection to the PbO2 with a silver
contact , perhaps also connect to the graphite substrate
so that any IR voltage drop between the two is nullified .

Of course a lathe is nice if you have one , and you could even use a rotary bur as your cutting tool for chasing the thread .....but none of that is simpler than rotating the rod by hand through a thread cutting die , if that can be
done easily enough . It wasn't special large threads I was thinking about , but standard 1/2" X 13 TPI coarse thread .

The whole idea of a polyester intermediate substrate is to get away from needing exotic pre-treatments
for the graphite , exotic electrolytes , surfactants which degrade and contaminate the PbO2 plating bath .

Any of the exotic refinements can be utilized additionally with no harm done , perhaps to improve the anode further if desired . However if a simpler and more easily made anode can last for months in service , then why bother with the extra trouble , but just make several of the simpler anodes ...replacing them when necessary ?

Has anyone tried mirroring or plating free metallic silver onto graphite as an interface between graphite and PbO2 ? It should oxidize in situ to silver oxide which is highly conductive . Or for the baking of chlorides scheme how about using the combination of silver doped tin , as there are also lead free soft silver solders that are 96%Sn and 4%Ag .


[Edited on 13-5-2007 by Rosco Bodine]

dann2 - 13-5-2007 at 16:05

Hello,

Thanks for patent. Will read up on it.

As far as Graphite is concerned I have lost all faith in it as a substrate as I think that (cloth/twine/rope wrap or bare) if you do not have a high quality coating of Lead Dioxide the (Per)Chlorates will 'get at' the Graphite and ruin the Anode.
Perhaps I am wrong.
I have read and been told about lots of (seemingly perfect) Graphite substrate anodes that fail soon after they are put to work.
I have make GSLD anodes myself that have looked *perfect* and they failed within hours of being put into a Chlorate cell. Perhaps I am a bit Anti-Graphite at this stage.
Only one guy I spoke to has made and used a GSLD (He would have use a fairly good set up).
He has since changed to Ti substrate though.

As far as Gouging rods are concerned my opinion is that they should be avoided like the plague. They are a very inconsistent product. They vary from manufacturer to manufacturer and from type to type. A guy (hello Allen!!) told me that there was Iron (or perhaps some other metal) in gouging rods that he had. Iron is bad news in a Lead Dioxide plating tank. They are OK for Cahthodes in Chlorate cells but not OK for Cathodes in Lead Dioxide plating tank(as they may have Iron particles in them).
At the very least use EDM (Electro Discharge Machine) Graphite.
Graphite is easy to put threads on using a simple treading nut from engineering supply store.

Has anyone else tried the 'Gilbert Pinkston Anode'.

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

It sounds like the ultimate in simplicity.

Cheers,

Dann2

Rosco Bodine - 13-5-2007 at 16:29

The *fact* is that graphite alone or even gouging rods alone can be used as anodes in a perchlorate cell , even without any PbO2 to improve their erosion limited life ,
which is more than a few hours , if the current density
is optimum . IIRC it was Mad Hatter who provided some
first hand data on this . So I am a bit doubtful concerning the dismissing of graphite as a substrate for PbO2 ,
given the numerous patents and commercial use .

Anyway I do have some EDM graphite in transit , and it is nice to know that it will thread okay ....I was thinking
it should cut like teflon , being self lubricating , about like
threading a candle stick :D , not quite as easy as cutting butter , but not too far from it , so long as the stuff didn't chip . I had a concern it might go snap crackle pop and
then wring the whole rod in two from any herky jerky little jolts and grabs as it is cutting . Another reason I
wanted to cut the thread by hand . Graphite is brittle ,
drop a piece on the concrete floor and it will break .

12AX7 - 13-5-2007 at 16:43

Heh actually I've dropped my graphite crucible (carved from a block of the stuff) on the floor from a few feet up and quenched it in water from orange heat. The only thing that it isn't particularly resistant to is oxygen...

Tim

Eclectic - 13-5-2007 at 16:48

Oh, I thought you were going to try 2-3" rod. 1/2" EDM graphite should be fine to thread by hand with a die. I have some 2" furnace electrodes that are like compressed charcoal, and would be iffy to thread even in a lathe.

I think silver and silver oxide dissolve readily in chlorate cells, while the SnO2 treatment seems to hold up for 600+ hours on Ti. I'm just thinking of it as a quickly applied coating on the graphite to avoid the "Dragon's Egg" composition PbO2/C interface.

Could someone do a quick check of 95/5 solder as a chlorate cell anode? (It CAN'T be THAT simple...)

[Edited on 5-13-2007 by Eclectic]

Rosco Bodine - 13-5-2007 at 17:33

Are you sure about dragons eggs being a reaction between carbon and PbO2 ? I was thinking that was something else ,
like an intermetallic reaction ...not carbon . Anyway that is a high temperature effect and I'm not sure it has a lower temperature much slower reaction parallel .

I didn't know there was any particular chemical interactivity between PbO2 and carbon at low temperature , and I was thinking that the oxidizing effect of PbO2 was not any real problem with graphite , but rather a physical separation , flaking off due to cracking or permeation of the electrolyte causing a physical delamination like water seeping between two polished sheets of glass .

Anyway , in another earlier patent US4101390 which I posted on page 8 I think , about the use of a bismuth oxide modified PbO2 finish layer being more erosion resistant , the patent stated that the initial PbO2 to graphite adhesion was best using PbO2 alone directly to graphite alone . I don't recall any patents referencing a need for any preliminary plating of the graphite with anything other than PbO2 , though some did speak of the need for special surface preparations like sanding the graphite with coarse sandpaper to roughen up the surface for better adhesion .

And in none of the graphite anode patents have I ever seen any problem described concerning graphite to PbO2 interface having electrical connectivity problems , except the
obvious connection loss when PbO2 layer cracks and
detaches , exposing the graphite to erosion . That bismuth oxide related patent also described an interrupted plating procedure , where a first layer of pure PbO2 was applied as a " primer " to the graphite , followed by transferring the electrode assembly to a separate plating solution containing bismuth nitrate along with lead nitrate , to plate a more erosion resistant
" finish layer " of bismuth adulterated PbO2 . That patent
also said it was best to begin the plating of the primer
layer of pure PbO2 in a low acidity high Pb content electrolyte at high current density , and as the plating got
heavier and the acidity increased and the PbO2 content
decreased to ramp the current density lower , particularly in the second phase .

I believe there are probably useful bits of information which can be gleaned from several patents , and combined to good effect at simplifying the process and improving the results .

Eclectic - 13-5-2007 at 17:56

No, I was just thinking out loud. Strong oxidizer in intimate contact with carbon with lots of current crossing the interface seems like it might contribute to loss of adhesion...

I'm all for lots of experimentation. (And making known the results)

12AX7 - 13-5-2007 at 19:33

I've heard that certain tantalum capacitors are rather nasty exploders. Reason being the Ta metal in contact with the MnO2 anode in dry types. Obviously, a dielectric layer of Ta2O5 seperates them, but if it somehow doesn't, and a lot of heat gets generated...(pop!)

Tim

Rosco Bodine - 13-5-2007 at 20:42

Check this out to see the kind of filter yarn I was
talking about , it is actually polypropylene fiber which
is probably even better than polyester . The patent mentions polypropylene fiber as one that works .

http://cgi.ebay.com/String-Wound-Sediment-Filters-10-x2-5_W0...



[Edited on 13-5-2007 by Rosco Bodine]

Carbon for Perchlorate

dann2 - 14-5-2007 at 17:33

Quote:
Originally posted by Rosco Bodine
The *fact* is that graphite alone or even gouging rods alone can be used as anodes in a perchlorate cell , even without any PbO2 to improve their erosion limited life ,
which is more than a few hours , if the current density
is optimum . IIRC it was Mad Hatter who provided some
first hand data on this . So I am a bit doubtful concerning the dismissing of graphite as a substrate for PbO2 ,
given the numerous patents and commercial use .



Edit: One square bracket added:P
I need to learn to use the preview button.



Graphite will make Perchlorate I agree. It is the wear rate that is (allegedely) the problem.
The report by MadHatter is here:

http://www.sciencemadness.org/talk/viewthread.php?tid=5050&a...
posted on 18-2-2006 at 06:53 PM

It reports low erosion rates.
The temperature of the cell is below 40C. (up to 40C)
That is a high temperature for graphite.

I don't know why he started his cell run at 9% Chloride.
Perhaps that is simply the mixture he happened to have and was not prepared to lower the Chloride concentration more by recrystallizing the Chlorate again (and again).
0% Chloride would be the best start but it is difficult (lot of work) to get homemade Chlorate with 0% Chloride in it.



Quote:-------------------------------
A little NaCl is mixed in because oxidation
of NaCl is more efficient than KCl.
End of quote-----------------------------

Why would Chloride be added to a Perchlorate cell??
Surely only Chlorate is wanted. Perhaps it's a typo.

Quote(From a few posts later)-------------------------------
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 Quote-------------------------------------

That's an incredible high current density for Graphite. It
is up and kicking with Lead Dioxide.
Also there is a problem with the current density/current into gouging rod. The surface area of the gouging rod (0.9525 cm diameter by 27cm long (usable lenght)) is 80.8cm squared.
At 0.2 amps per cm squared that would be a current into rod of 16 amps, not 7 (as stated). [hope math is correct]

When the rod wears a bit and gets thinner the current density will go even higher if current is kept constant.

MadHatter also produced 8lbs of Perchlorate using 6 gouging rods. That is a very impressive wear rate. (More than one pound of Perchlorate using one gouging rod.)
I have heard of people wearing more carbon making Chlorate.
If Carbon is that good it is a wonder why anyone (myself included) would bother with Lead Dioxide, Pt, etc etc.

There is some journal articles refs regarding Perchlorate making using Graphite at this page (at bottom):

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

Sihvonen, G., Suomen Kemistilehti, 10B, 27 (1937)

and

Ullman, Frits, "Enzyklopadie der technischen Chemie", Vol. 3, p 299-307, Berlin, Urban & Schwarzenberg, 1929

Anyone got access to them?


DANN2

[Edited on 16-5-2007 by dann2]

12AX7 - 14-5-2007 at 19:43

Where is your post/did you even write anything outside of that quote box!?

dann2 - 15-5-2007 at 16:55

Quote:
Originally posted by 12AX7
I've heard that certain tantalum capacitors are rather nasty exploders. Reason being the Ta metal in contact with the MnO2 anode in dry types. Obviously, a dielectric layer of Ta2O5 seperates them, but if it somehow doesn't, and a lot of heat gets generated...(pop!)

Tim


Hello Tim,

I think the Ta capacitors (they have a polarity) explode when you connect them the wrong way around.
Perhaps there are not porarized types nowadays (its been a long time since..............)

Cheers,
Dann2

Dann2 have you looked at Beer's patents?

jpsmith123 - 18-5-2007 at 15:32

Beer had several patents regarding MMO anodes.
I'll attach one of these patents that has several interesting examples:

Example II involves a graphite substrate for a MMO coating.

Example XVI involves electrolysis to apply the MMO coating.

Example XVII apparently doesn't involve any platinum group metal oxide.

Attachment: 3632498_OCR.pdf (728kB)
This file has been downloaded 1101 times


dann2 - 21-5-2007 at 12:41

Thanks for patent.

MMO is Chlorate only.
I have been running an MMO (CORROSION CONTROL WIRE)
anode for about 3 weeks in a cell in an attempt to make Perchlorate.
Ir oxide and Ta oxide I believe. The cell is almost pure Chlorate, just some Chloride.
No Perchlorate has formed.

Dann2

12AX7 - 24-5-2007 at 16:05

What's the poop, is it making oxygen instead?

Attempt to make Perchlorate with MMO (DSA) anode

dann2 - 24-5-2007 at 17:36

Hello,

I presume it is making Oxygen at the Anode and Hydrogen at the cathode. There comes lots of gas from both electrodes.

The black coating was removes on some of the surface of the Anode. (Anode is black when new.) Black coating that was not removed was just sitting there, it could be wiped off with a slight rub of a cloth. There is still an active coat on the anode though as it still emits gas when in a cell.

Anode is similar to www.lida.com wire anti corrosion anode.

Edit: Should be www.lidaproducts.com

Cheers,
Dann2

ps. what does poop mean?

[Edited on 26-5-2007 by dann2]

hashashan - 26-5-2007 at 07:23

Some more questions about a good connection.
Any ideas of how to plate silver on the anode without the rochelle salt?
no electro deposition available?

Esucll - 26-5-2007 at 12:57

Ok guys this is my first post in this forum..

PbO2 electrodes aren't the same rods consisting the core of commercial AA or AAA batteries?

dann2 - 26-5-2007 at 13:44

The core of theses batteries is Graphite.

You can use it to make Chlorates (and perchlorate with more wear)

Some info here:

www.geocities.com/kkwolly

Dann2

alancj - 26-5-2007 at 14:11

Quote:
Originally posted by hashashan
Some more questions about a good connection.
Any ideas of how to plate silver on the anode without the rochelle salt?
no electro deposition available?

I don't know... but Rochelle salt isn't hard to make. Just neutralize cream of tartar (potassium hydrogen tartrate) with sodium carbonate. Filter any insolubles and then you've got your Rochelle salt (potassium sodium tartrate). You can then recrystallize the salt for increased purity.
The only other electroplating baths for silver use cyanide, which nobody is going to sell to you... which means making it... and I don't know if that can even be used to plate on PbO2. There is a thread on making cyanides btw.

-Alan

[Edited on 26-5-2007 by alancj]

hashashan - 26-5-2007 at 22:14

cyanides are off the topic ... the lead is enough hazard for me.
I know thte rochelle salt is easy, but i dont have any tartarates, yes i can buy them. However i prefer not to.
The interesting question is why is it problematic to plate silver on PbO2? will it disintegrade if it used as a cathode? what if ill first color it with the silver paint?
i just want to be able to solder a wire to it.
maybe silver paint and then electroplate copper?

alancj - 27-5-2007 at 00:11

Gee... don't you like the smell of HCN in the morning?

Buying cream of tartar and baking soda (roast to get sodium carbonate) at the grocery store is neither expensive nor suspicious. It is also required of the only procedure that I know of that is claimed to coat PbO2.

Maybe precipitated silver powder could be used to make your own silver paint. Mix the powder with a small amount of silicon oil, and apply between a copper strap and the PbO2 electrode. I don’t know about soldering… PbO2 has a low decomposition point (290C), so you can’t get it too hot. Maybe dusting the surface with silver and then pour a low melting wood’s alloy around that for a connection.

Yes, I think the problem is that PbO2 disintegrates as a cathode… at least if you tried using it as a cathode in a (per)chlorate cell. However, in the procedure described in US Pat # 3,318,794 (that I think you are referring too) the lead dioxide anode is used as a cathode for the electrodepositing of silver on the surface of the PbO2 anode. So it couldn’t disintegrate in this case. Perhaps the current density is low enough, or maybe it has something to do with the fact that the anodes these are being applied to are plastic-bonded PbO2-powder “massive” anodes. It might not even work on electrodeposited PbO2. It’s something that just needs to be tried IMHO.

-Alan

Dann2 have you tried MnO2?

jpsmith123 - 27-5-2007 at 16:58

Supposedly MnO2 can be electrolytically deposited on a graphite substrate (or other substrate, although I understand it sticks to graphite very well) from an aqueous MnSO4 solution, but it is the gamma form.

Then you could heat it to 300 degrees C or so and convert it to the beta form.

Maybe that's worth a try?

The thought just occured to me: Maybe for a quick test of the perchlorate making ability on MnO2 you could buy a chunk of the mineral pyrolusite somewhere (I think I've seen some fairly big pieces for sale/auction on ebay). Pyrolusite is a naturally occuring form of beta Mno2.

[Edited on by jpsmith123]

Rosco Bodine - 27-5-2007 at 20:40

Regarding the silvering , never tried it , but ....

Possibly you could simply dip the portion of the electrode wished to be silver plated in a SnCl2 silvering catalyst ,
and then immerse that portion in a silver nitrate ,
ammonium hydroxide and hydrazine sulfate electroless
plating bath . You should get about a 60 micron (.0024 inch) plate in 4 hours .

There are other silver "mirroring" methods . IIRC there is a
document on this in the forum library . I am not sure ,
but it seems like I read that some of the electroless plating baths can also be driven with electricity when the substrate to be plated is conductive .

Attached is an article concerning silver electroplating via a process which uses relatively common materials and involves
no cyanide . The process can be used to selectively plate out
silver from silver-copper alloys which have been dissolved in nitric acid , for example using coinage silver or sterling .
But there seems to be no reason why the same method would not work for a pure silver process also .

There's a bit more concerning plating from a straight silver nitrate solution on the following page
http://antoine.frostburg.edu/chem/senese/101/redox/faq/ag-fr...

[Edited on 29-5-2007 by Rosco Bodine]

Attachment: JCE Volume 36, Number 6, June 1959 Electrodeposition of silver and copper without the use of cyanide.pdf (2.4MB)
This file has been downloaded 1777 times


Electroless Silverplating

Rosco Bodine - 28-5-2007 at 08:12

That book on electroless plating must be on the forum FTP
because I didn't see it in the forum library .

The entire book is a 22 MiB file , so I made a smaller file
for just the chapter on silver .

I extracted the chapter on silver mirroring and am attaching it here .

What I said before about using electricity in combination with the electroless process may have been similar to the contact process , which simply causes the initial coverage to form on a targeted area exposed to the plating bath . And once that
coverage completes the plating proceeds autocatalytically .
So it may be that what I was describing as the usefulness of electricity in combination with an electroless bath , was as a
substitute for the initial deposition catalyst , to kick start the
initial coverage . I really don't remember the context in which electricity may be used in combination with the electroless plating bath .....except that it definitely can be used when the substrate is conductive .

Attachment: Electroless Silverplating Chapter from electroless_plating_-_fundamentals_and_applications.pdf (695kB)
This file has been downloaded 18292 times


dann2 - 28-5-2007 at 16:38

Quote:
Originally posted by jpsmith123
Supposedly MnO2 can be electrolytically deposited on a graphite substrate (or other substrate, although I understand it sticks to graphite very well) from an aqueous MnSO4 solution, but it is the gamma form.

Then you could heat it to 300 degrees C or so and convert it to the beta form.

Maybe that's worth a try?

The thought just occured to me: Maybe for a quick test of the perchlorate making ability on MnO2 you could buy a chunk of the mineral pyrolusite somewhere (I think I've seen some fairly big pieces for sale/auction on ebay). Pyrolusite is a naturally occuring form of beta Mno2.

[Edited on by jpsmith123]


I have never got around to trying MnO2. Spending too much time thinking/talking about the stuff. I need to get my hands dirty a lot more (Lead Dioxide work excluded:-|)

Would the Pyrosusite be conductive enough I wonder.

I am currently running a graphite (lump of edm) anode cell making Perchlorate to see how good it is and how much it wears.

Dann2

jpsmith123 - 28-5-2007 at 17:40

I have a cell that I made from a pool chlorinator just sitting here, which I can't really experiment with until I move out of this small apartment, hopefully sometime this summer.

As far as the pyrolusite, I've been trying to find some information about the conductivity, but so far no luck.

BTW, with regard to your graphite anode cell, did you start with chloride or chlorate?

alancj - 29-5-2007 at 00:15

Quote:
Originally posted by jpsmith123
I have a cell that I made from a pool chlorinator just sitting here, which I can't really experiment with until I move out of this small apartment, hopefully sometime this summer.


If you are worried about it producing chlorine then just raise the pH of the solution with some NaOH, and it won't produce any chlorine. It will basify by itself but when starting out with a neutral solution it will still generate enough Cl2 to be quite irritating before the pH gets up around 8-9. The current efficiency will suffer, however (but an anode just sitting around has a current efficiency of 0! :))

-Alan

A patent mentions silver plating used under alpha? lead dioxide

Rosco Bodine - 29-5-2007 at 09:12

A few times I have mentioned the idea of using metallic silver or silver oxide as an interface material , a conductive substrate or possibly as a highly conductive dopant in mixture with other oxides . But I haven't been able to find any mention at all , much less any details of this idea having been tested in anode construction ......until now anyway .

One brief sentence in US4064035 mentions the use of a silver mirror interface to improve the conductivity between a titanium substrate and lead dioxide , but provides no details whatsoever . See page 3 , column 3 , lines 34 to 36 .
For context the paragraph describes anode substrate preparation , which involves degreasing prior to plating with lead dioxide , and goes on to say that such pretreatment may be omitted when an alkaline plating bath for alpha lead dioxide is to be used for the first layer . However , the patent states
Quote:
Where the electrical conductivity is particularly required, the substrate is desired to undergo said pretreatment followed by a treatment for silver plating


It is unclear to me whether this silvering necessarily applies to subsequent plating with either the alpha or beta lead dioxide specifically , or both . But the technology more generally described by this patent is the basis for the method advanced later by other patents including those which were the basis for alembics titanium substrate anodes having the stress relieved combination of alpha and beta lead dioxide layer construction .

Further , tin oxide does function as a silver deposition catalyst as described in the electroless silvering literature .
Not only is the tin oxide present on the titanium substrate
from the tin chloride dip and bake treatments , which produces a continuous coating for which silvering would have
a high affinity and adhesion ......but tin oxide would also be
deposited in trace amounts sufficient for catalysis of silver mirroring , when a substrate having any silica content is
simply dipped into a tin chloride solution .....no baking required as a pretreatment for mirroring with silver .

I believe this silvering scheme could be applied to many substrates such as ceramics which have some natural silica content which would be reactive with a tin chloride dip treatment , as activation for a silvering interface , between a substrate and whatever form of lead dioxide is subsequently electrodeposited onto that silvering . This might also apply to ordinary gouging rods , whose porous surface might even be an advantage . A carbon or a porous ceramic possibly could be dipped into water glass , and then into an acid to form silicic acid in situ in and on the surface , then dipped into tin chloride to deposit the tin oxide catalytic sites for silver deposition as an adherent and conductive interface layer for the lead dioxide to be subsequently electrodeposited to complete the anode .

One of the ideas that has occurred to me is that a plain glass
stirring rod could be dipped into tin chloride and then mirror plated with metallic silver , and used as an inert physical substrate upon which to electrodeposit a massive lead dioxide anode . Or a flat piece of unglazed one foot square
ceramic floor tile could be cut into 3 inch wide X 12 inch strips . Anyway , seeing the however brief reference in the
patent is encouraging because it indicates that silver plating specifically is at least one material which can be used as a conductive "primer" layer onto which lead dioxide may be plated . This makes available as anode substrates any
material conductive or not by itself , which may be mirrored with silver to give it at least temporary conductivity and allowing a more durable layer of lead dioxide to be deposited , which may subsequently be built up to any desired thickness as a massive or embedded substrate massive lead dioxide anode .

hashashan - 29-5-2007 at 12:22

i believe that if it is possible(ive also heard about it) then you have to remain a perfect neutral PH because even dilute nitric acid will easily dissolve the very thin layer of silver.

Rosco Bodine - 29-5-2007 at 12:58

The alkaline alpha lead dioxide plating bath based on
tartarate , acetate or plumbate would get around that .

I don't recall which type lead dioxide was plated out from a sulphamate bath .

Also , I wonder what might be the result of plating from a basic lead nitrate buffered normal lead nitrate bath ,
or even a basic lead nitrate / normal lead acetate bath .

Another idea I have for a stress relieved deposit , is using
a combination lead salts bath from which the alpha or the beta lead dioxides are precipitated preferentially at slightly different curent densities . An unfiltered and unregulated but limited rectified DC from a transformer ,
might deposit the alpha lead dioxide during one part of the power waveform as the current changes and then
deposit beta lead dioxide in another part of the waveform , so that the alpha and beta lead dioxides are
continually electrodeposited as a mixture . There could be an optimum power frequency and ripple waveform profile which plates out an idealized mixture of alpha and beta dioxides , which could be plated to any thickness desired , as it would be internally stress relieved at a microstructural level .

Another idea I have is that a vibrator could probably be useful for mechanically dislodging tiny bubbles of oxygen
which might form pinholes on an anode being plated with lead dioxide . The first sort of simple vibrator which came to mind is the sort of vibrator used in cheap aquarium pumps , where a magnet attached to the end of a leaf spring resonates in the rapidly reversing field at the
end of a small AC solenoid coil . There is probably a
resonant frequency peculiar to each anode structure
where the effect would be optimum , but I believe just
the generic vibration of an AC coil and magnet might do the trick well enough to be useful .

dann2 - 29-5-2007 at 19:23

Quote:
Originally posted by jpsmith123
I have a cell that I made from a pool chlorinator just sitting here, which I can't really experiment with until I move out of this small apartment, hopefully sometime this summer.

As far as the pyrolusite, I've been trying to find some information about the conductivity, but so far no luck.

BTW, with regard to your graphite anode cell, did you start with chloride or chlorate?


Hello,

Don't know if this is directly related to the Pyrolusite but you can purchase (natural) Magnetite in crystal shops, ebay etc but it is non conducting. It is the few % of other stuff in it that makes all the difference for electrical conductance.

The Graphite Anode Perchlorate cell was started with 'pure'
Chlorate.
Pure in this case meaning Chlorate that was recrystalized twice from a Chlorate cell. I boiled down the Chlorate solution until crystals started to form. The solution was let cool and then cooled to about -10C. The crystals were filtered in a cloth and quickly washed in cold water.
Crystals were dissolved in water again and solution boiled down etc. (Two crystilizations).
A solution of 500 grams of this Chlorate per liter of water was used as the start solution for the Perchlorate cell.
It tests positive for Chloride when a Silver Nitrate test is done.
I would have liked to have a zero Chloride content in the cell at the start but I got fed up with the crystalizing . I guess you could argue that the solution I used in the Perchlorate cell is what an amateur will usually have.
I have kept samples of the starting solution which I intend to test with Silver Nitrate (how??) to get an idea of the Chloride % in the solution at the start of the Perchlorate cell run.
The Graphite is wearing at a fairly linear rate of about 23 grams per 24 hours.
Current density is approx. 33mA per square cm.
Temp about 26C. Cell is sitting in a bucket of water.
pH uncontrolled (about 6 to 7)
Cell is two liters.
SS cathodes.
Computer power supply (5v) with Nicrome resistor (hot!)
to keep current fairly steady. Voltage accross cell about 3.6 volts.
The cell ran for about 1.5 days before Perchlorate started to show using Methylene blue test.
The cell has a 'run time' of about 50 hours. (I reckon)

Cell still running.

To get back to testing for Chloride. I do not have a large amount of Silver Nitrate. My scale only goes to the nearest 0.1 of a gram therefor it is not practical to measure Chloride content using Silver Nitrate by weigning PPT of Silver Chloride.
I was going to do the following.
Make up a fairly dilute solution of Silver Nitrate.
Make up a range (say twenty litttle bottles ) of solutions of
NaCl solution going from 0.5% to 10% Chloride in 0.5% steps.
Put them in a row (drum roll starts HERE!!!!!!!!!!!!!)
I will then put a drop of the Silve Nitrate into each bottle which will give me a certain (hopefully noticably different)
opacity/white colour.
I will then compare the row of bottles to what a sample from my Perchlorate cell start looks like after a drop of the Silver Nitrate soluton has been added.
Would this work do yis think.
The solutions of NaCl and Silver Nitrate need to be dilute (I can use a very dilute solution of Silver Nitrate) so that a fine ppt of Silver Chloride is formed. If the solution are too concentrated you get lumps (literally) of Silver Chloride forming which are useless as a visual representation of the Chloride content.

All rather crude but easy to do (If it will work).
I only want to find out the Chloride content to the nearest percent or so.

Suppose I could purchase a scale to .01 gram.........

Dann2

not_important - 29-5-2007 at 20:49

You need to keep the chloride concentration low enough that not all the silver is precipitated, otherwise all the silver drops out leaving some amount of chloride in solution.

You'll want to do some constant dilution of the references and test solution, such as
1:100. Make the standards, and the test solution, using large enough amounts you can accurately weight them. Then take say 1 ml of the each solution and add it to 200 ml of DW, and test 1 ml of that. Start with one of the reference solutions and see if the result is dilute enough that a drop or two of AgNO3 solution ppts all the chloride - add one drop, let the ppt settle, add another drop of AgNO3, and so on. You can work the maths to see about how much chloride can be in a ml for a known amount of the AgNO3 solution to full ppt all the chloride; do that for the highest concentration so that all the more dilute solutions will also have all their chloride knocked down.

A method sometimes used is to use a long tube holding the (diluted) solution under test, and look into it from above at a lighted target. Using a second tube, slowly add reference solution (again diluted) until the target is as hidden by the opacity to the same degree as by the solution under test. And alternative is to side-light the tubes with a diffused linear light source, such as a fluorescent lamp or illuminated wall, and adjust the amount of solution in one tube to give the same brightness of light scattered by the AgCl as the other tube - works with very dilute solutions.

garage chemist - 30-5-2007 at 06:17

What is "butyl titanate" supposed to be? The reaction product of TiCl4 and n-butanol?

And is Ruthenium one of the more expensive PGMs, or is it on the
affordable site (like, more or less expensive that Pt)?

I'll probably buy some titanium sheeting from ebay today, theres a bunch of it on there ATM.
And start making a DSA (MMO) anode, which doesnt sound difficult at all from the patent. You only need the ruthenium chloride and TiCl4. What do you think, should I try it?

Eclectic - 30-5-2007 at 09:34

Ru MMO's won't make perchlorate AFAIK, just chlorate.

Ru is not so expensive as PGM's go, but finding someone who will sell a small amount is almost impossible.

Antimony/Tin oxide on titanium seems just as effective, easier to produce, and MUCH cheaper.

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