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Author: Subject: More on PbO2 electrodes
Battle
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mad.gif posted on 9-4-2005 at 17:26


looks like I stumped the croud! Does anyone have anything???????????
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[*] posted on 9-4-2005 at 22:02


It may not be a case of 'stumping' the crowd, but rather, not getting their interest. :)

Are you saying you want to produce a PbO2 coated electrode? In RS's Chlorate thread vulture mentions making a PbO2 electrode by electrolysing Pb in dilute H2SO4 (so as to not produce the sulfate), thus producing a PbO2 coating. Hope that helps.

Good luck anyway.




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[*] posted on 10-4-2005 at 01:28


Thanks!

I have been working on a process for several years now and I have been able to plate what I beleave is a very nice layer of alpha lead, but I cannot find any back up data on the web.

Alpha lead is gold looking is it not? :o

I will search the string.
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[*] posted on 10-4-2005 at 13:56


From what I've read you want the Beta form, because of its higher conductivity.
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Rosco Bodine
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[*] posted on 11-4-2005 at 22:31


The question is about something simple .

You have two electrodes of sheet lead
in a sulfuric acid electrolyte . The anode
will build up a layer of brown lead dioxide
and the cathode will build up a layer of
spongy lead bare metal . You can run the
cell with the polarity normal for a period of
time and then reverse the polarity and repeat the process to condition the electrodes , prior to using them in the
actual reduction . Supposedly this treatment improves the conductivity and efficiency of the cell , and reduces the
corrosion of the electrodes . There is an
appropriate current density recommended
to achieve the effect and it will be stated in any good reference for electrochemistry , how many Amps and for how long , per square centimeter of
electrode surface in a given concentration
range of electrolyte . It's been years and I don't recall what the values are , but I do remember it takes a hefty power supply and some water cooling for the cell
to keep it from boiling .
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[*] posted on 12-4-2005 at 01:10


I am very familiar with the battery formation process but what I am looking for is information on the electrodeposition of lead dioxide onto a lead alloy substrate using lead nitrate chemistry simialr to that used for making a clorate cell electrode. Has anyone ever tried a different materal, say lead, other than carbon or platinum when making the clorate cell electrode?
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[*] posted on 12-4-2005 at 01:11


Sorry! Chlorate
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cyclonite4
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[*] posted on 12-4-2005 at 01:46


I recently found a website about making a PbO2 anode for a chlorate cell: http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/leaddiox/leaddioxide.html



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[*] posted on 12-4-2005 at 02:31


The same website was quoted by axehandle in the thread regarding chlorate production, but it has improved a lot from then. I wouldn't like to be a prick but doesn't such a thread already exist? We have previously discussed the manufacture of a PbO2 plated electrode. I will try a procedure I had discussed with axehandle later on this summer, where a graphite powder-PVC electrode covered with PbO2 powder will be plated by PbO2 making a homogenous layer. The guy who made the website mentioned also thought of something similar, where a plastic sheet (from some floppy disk if a remember correctly) was coated with a layer of PbO2 by dissolving the surface with acetone. Axehandle tried a perspex substrate, but being easily inflammable due to the oxidizing conditions (PbO2) it didn't succeed.



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[*] posted on 12-4-2005 at 05:17


The Geosite page has been referenced many times and to this day, I do not think anyone knows who this guy is but he has obvioulsy spent a large amount of time in his garage!

The unique question here is Lead Alloy substrate not graphite or carbon. The plastic idea is very cool but again it is graphite or carbon that is basically acting as the substrate and current conducting means.
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[*] posted on 12-4-2005 at 05:55


Just read the entire string and it was like watching a mini seris move. Axehandle had me on the edge of my seat, and then fire!

In any case the entire string kept dancing around the possible use of lead or lead alloy as the substrate. If it can be made to work, there is more out there for its use than just perclorates!!!!!!!!!:cool:

Anyone have a cell that they can try this on? I have several ideas that may make it a little easier if you are interested.
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[*] posted on 12-4-2005 at 06:38


Just give us your ideas. I have a cell, but it is still on paper right now. I do not have neither the time nor the budget to set-up the large scale cell I am planning right now (must wait till summer), but if any suggestions are available they are welcome. That's the way we work around here.

[Edited on 12-4-2005 by Esplosivo]




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Rosco Bodine
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[*] posted on 12-4-2005 at 08:00


Just a thought about a possible alternative .

Ceramics artists use a colloidal gold glaze
as decorative trim on the edges of plates and cups and saucers . In the heat of firing , the gold actually melts into a deposited mirror film of pure gold . Perhaps a graphite crucible or rod could be coated with a layer of this gold ,
and fired to produce a durable plating . An electrodeposited gold plating could possibly be fired to sinter and fuse it
in the same way , to build up a heavier
and nonporous film of plating .

There is also a thin gold foil used by bookbinders and sign artists who do the
gold lettering on glass doors , " gold leaf "
material which may have usefulness for
coating an electrode , and then fired to
form one solid continuous film . Colloidal
gold might even serve as a hot melt adhesive for firing gold leaf onto a graphite substrate . These would be
expensive experiments :D

I have never tried the production of perchlorate , but have used a lead electrode cell for reductions of organic nitro compounds to amines . Those reductions were done using a divided cell
having a porous cup which was the compartment containing the cathode and
catholyte . The cell design was a coaxial
arrangement , with a sheet lead cathode wrapped around a glass bottle fitted with
a two hole stopper through which was circulated cooling water . The sheet
lead was cut in an " L " shape so that
when the long leg was wrapped around the bottle , that portion was immersed in the electrolyte , and the short leg of lead sheeting extended upwards rising above
the surface of the electrolyte to provide
a connection point for the alligator clamps . The cathode and cooling bottle
stood inside a terra cotta flower pot which
functioned as the porous cell . This assembly sat in a larger glass bowl which
held the anolyte and a sheet lead anode having a connection riser tab for the anode connection . There was never any
corrosion of the lead dioxide anode during
many reductions using that arrangement ,
although the cell operating conditions were very different from a perchlorate cell . The coaxial arrangement of the electrodes was found to be advantageous
for reasons of electrical and thermal efficiency . So I share this information
for its possible value , adaptability to
use in the perchlorate cell .

[Edited on 12-4-2005 by Rosco Bodine]
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[*] posted on 12-4-2005 at 20:46
Gold


That's an interesting point about gold. It melts at 1948 F. My electric kiln easily exceeds
that. I may have to give it a try although I know the glaze will not be cheap !




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[*] posted on 12-4-2005 at 22:17


Gold film, the really thin type which can be bought at a professional jeweller, can be melted easily over a normal bunsen flame and adheres well to many surfaces. Although being an excellent idea I doubt it can be used in such a cell because of the high chloride conc. the gold layer would most probably erode, although I am not sure about this. Also I do not know if PbO2 adheres very well to gold, and may lead to many exposed areas. Gold film is not that expensive (thanks go to axehandle for taking away my 'phobia' about these rare metals :P).



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[*] posted on 12-7-2005 at 04:22
Any Successful PbO2 Anodes Here?


After reading everything related to PbO2 anodes I could find here, I get the impression that no one has yet produced a functional anode.

It seems to me that the most reliable anode might be one with no substrate, i.e., an electroformed "massive" PbO2 anode, but what kind of substrate is there that could get be used to form the anode and then be easily removed later?

BTW, here are some papers that not everyone may have seen:

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

http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...
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[*] posted on 12-7-2005 at 05:40


Something else interesting I tried last night, I took a 3/16" steel rod, sanded off the rust ;) and heated it to redness (giving it a black coat of Fe3O4). Hooked it up to a salt cell and lo and behold, both electrodes started bubbling, giving the smell of chlorine. :D Checked it this morning to find it mostly eroded though.

Scale can get pretty thick on iron, it also tends to flake off though. Maybe orange to yellow heat for 20 minutes followed by a linseed oil treatment? If it were this easy, industry would be using it though...

Which reminds me, I need to grab some magnetite and arcmelt it into a lump and see how bad it fractures.

Tim




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[*] posted on 14-7-2005 at 05:35


I found another forum where people have been discussing making perchlorate by electrolysis:

http://www.ukrocketry.co.uk/forum/lofiversion/index.php/t426...

After reading through it (and doing some other reading), I've come to several conclusions:

(1) The platinized titanium mesh anodes (which are intended for rhodium plating for jewelry purposes) are useless (as is), for serious chlorate or perchlorate production.

Apparently the Pt layer on these is just way too thin for anything except light duty plating.

If there are no bare spots, this mesh may be a good substrate for PbO2, but I wouldn't doubt that the platinum layer on a typical mesh anode like this is spotty as well as thin.

(2) A platinized Ti or Nb anode from a pool chlorinator may work as it is, in a ClO3 or ClO4 cell, or better yet as a substrate for PbO2, but these seem very hard to find.

(3) A GSLD anode is quite effective and reliable if properly made, but making it properly apparently means rotating it during the PbO2 plating process (using no surfactant), which is a significant inconvenience. Moreover, it is hard to tell by visual inspection alone if you've succeeded in making a good GSLD anode.

(4) The graphite of even a well made GSLD anode will erode somewhat in the area where the PbO2 plating ends.

Anyway, it seems to me that the best and most practical anode would be either PbO2 with no substrate (but how do you do that?); PbO2 over platinum or platinized wire; or PbO2 over ceramic.
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[*] posted on 21-7-2005 at 07:27
Tantalum Rod Substrate


Well, I just ordered some tantalum rod.

I ordered 6" of 0.09 inch diameter tantalum...and it's expensive.

I think I will try to plate it using a lead acetate bath. Hopefully I will be able to build it up to 0.5 inches or so and then remove the rod.
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[*] posted on 21-7-2005 at 11:32


I used 25cm of 0,3mm diameter platinum wire (weighs only 0,38g so not that expensive) to make 156g of KClO4 (from commercial NaClO3 from france, I used 250ml of a 45% solution, containing 155g NaClO3) in 4 days (96h) with artificial mixing of the electrolyte (very important in perchlorate cells, this raises the efficience considerably).
The current was 1 Ampere because the current density would have been too big at the Pt if the current was higher.

Look here for the design:
https://sciencemadness.org/talk/viewthread.php?tid=4138

Or go to www.versuchschemie.de/index.php
and look in the topic "Meine Perchloratzelle" for more details.


I think making a PbO2 anode is not worth the hassle, just buy some Pt wire and you're done.
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[*] posted on 21-7-2005 at 17:31


Hello Garage_chemist,

I'm glad to to see you had success with your cell.

I debated using platinum (and I may still try it, since I have some) but I was planning on starting with salt, so I thought PbO2 would be better.

From what I read, I could probably use platinum if I do it in two steps, avoiding low chloride concentrations that would dissolve the platinum.

In any case, have you seen the following article? If you're using platinum in a perchlorate cell, it looks quite efficient, even without adding dichromate or persulfate.

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

BTW, how difficult is it to seal platinum wire into soda-lime glass? Did you have any problems?

Joe
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[*] posted on 21-7-2005 at 17:53


It should be easy for anyone with basic glassworking skill, as Pt and soda-lime glass have (almost) the same thermal expansion coeficient.
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[*] posted on 21-7-2005 at 18:52


Well unfortunately I don't have what I would call "glassworking skill" (although I have dabbled with soldering things to glass).

I'm aware of the relatively good match between the thermal expansion coefficients of platinum and glass.

My question was primarily in regard to the need of any special cleaning or surface preparation to insure that the glass properly "wets" the platinum.
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[*] posted on 22-7-2005 at 02:06


I had absolutely no problems melting the Pt wire into the glass. No preparation, nothing, and it was completely tight and no liquid got to the connection.
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[*] posted on 10-8-2005 at 14:59


if you guys go to the uk forum and the google pyro group and read ALL the posts by gilbert pinkston you will be making O4 at will (with some work) from Cl or ClO3 some of the ideas here are nothing short of bazaar i don't know what the problem is my way may not be the best but it works and it's low tech and cheap!! Pb is $0.06 a pound at the scrap yard and HNO3 is cheap and easy to make
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