Sciencemadness Discussion Board - More on PbO2 electrodes

More on PbO2 electrodes

Pages: 1 2 3 .. 12

janger - 22-8-2004 at 21:19

Has anyone had luck preparing their own PbO2 electrodes?

The refs I have say after completion, the electrode should be shiny black. Yet, other refs say PbO2 by itself is brownish.

I have achieved a coating on a carbon rod from a fairly simple procedure, although it wasn't a well conducted experiment. All chemicals are easily available. It is chocolate brown in color. After sitting for several days, it seems to have adhered fairly well.

AFAIK, it must be the dioxide. Can anyone tell my if this might be correct?
I will see how it holds up in a chlorate cell.

If anyone is interested, I'll post more details on the procedure.

Dave.

Esplosivo - 23-8-2004 at 11:12

I have discussed with axehandle a method of making a PbO2 electrode. I don't know if he has tested it yet. On my part I made a small electrode using the procedure I am going to mention.

The procedure basically involves dissolving PVC in MEK and then adding finely powdered graphite. This 'liquid' PVC mixed with a high proportion of graphite is then made into a slurry. The PbO2 is made to adhere to its surface by 'sprinkling' it on the surfaces of the liquid slurry. A wire with an exposed part is then inserted in the slurry and the whole thing is left to dry in the sun.

I did not have the time to experiment with different ratios of 'dissolved PVC':'Graphite powder'. I simply mixed used the aprroximate ratio of 2:1. The formed electrodes held quite well, though one of them was fragile (probably due to a lot of graphite powder). The surviving electrode I made is quite small. When I'll have the time I will try to build larger ones.

[Edited on 23-8-2004 by Esplosivo]

janger - 23-8-2004 at 15:33

That sounds an interesting idea. Did you get a chance to measure the resistance of the electrode? Can you explain how all surfaces of the slurry are coated in PbO2?

Dave

axehandle - 23-8-2004 at 15:48

After having that nice idea about conductive plastic, I found that someone had already done lots in that area. Check out this guy's homepage:
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

His plastic substrate PbO2 anodes are made by smearing THF on the surface of the substrate, rolling it in PbO2, then letting the THF evaporate, then electroplating a nice thick layer ontop of the "painted-on" layer using lead nitrate.

No reason it shouldn't work with any Pb(II) salt, like Pb(Ac)2...

Making the whole block conductive with graphite would have the somewhat huge advantage of making it VERY much easier to provide a reliable connection to the cell once the anode is in use, I'd think.

[Edited on 2004-8-23 by axehandle]

Esplosivo - 23-8-2004 at 23:24

Quote:

Originally posted by janger
That sounds an interesting idea. Did you get a chance to measure the resistance of the electrode? Can you explain how all surfaces of the slurry are coated in PbO2?

Dave

Sorry Dave, but I didn't experiment with it a lot. Right now I do not have as much free time as I wish.

I have a simple question. When electroplating with PbO2, the substrate being plated should be + or - charged. Last time I did this, the lead on the anode 'dissolved' while lead was formed at the cathode. Was there something wrong with the concentration of the lead (II) ethanoate solution I used? It might have been somewhat dilute. Thanks for the help.

[Edited on 24-8-2004 by Esplosivo]

janger - 23-8-2004 at 23:56

Quote:

Originally posted by Esplosivo
I have a simple question. When electroplating with PbO2, the substrate being plated should be + or - charged.

It should be the anode (+). Otherwise as you found, lead metal would be deposited, which ain't what you want.

In some procedures, especially in nitrate baths, copper salts are added to the electrolyte. The theory goes that copper first plates out on the cathode. As the concentration of copper falls, lead will begin plating out. But this forms a sort of miniature electrochemical with the copper, causing the lead to dissolve again! This isn't really necessary. Just means you need less lead.

I tried some of my impure lead acetate today using carbon electrodes (both of them). Sure enough lead began covering the cathode. I switched off the power to see what would happen. In a few minutes the lead had been replaced by copper. I did get (presumably) PbO2 on the anode. However I hadn't cleaned the carbon rod properly and it didn't adhere very well.

So you've tried creating electrodes using the acetate? I'd like to hear more.

Dave

Esplosivo - 24-8-2004 at 04:10

Quote:

So you've tried creating electrodes using the acetate? I'd like to hear more.

I actually did try, but as you might have noticed the attempt was unsuccesful. Thanks a lot for the help. I will try this procedure out soon, I hope.

Axehandle

MadHatter - 24-8-2004 at 14:23

I saw that page and downloaded to my PC some time ago. It looks
promising as there are several methods to create an anode using
PbO2. I haven't tried this recently as I have all of the KClO4 I need
for the moment. Great post in any event ! I've done it with gouging
rods but the erosion rate is extremely high if the cell exceeds 40 C.
Also, adding sodium fluoride or potassium persulphate increases
the efficiency of the cell.

My idea for my next anode is to dissolve a plastic(probably with acetone)
for use as a binder for MnO2 or PbO2. I need a plastic that won't be
attacked by the chlorine or oxygen created during the electrolysis.

Janger, sounds like your ready to rock with your anode ! GO FOR IT !

[Edited on 24-8-2004 by MadHatter]

axehandle - 24-8-2004 at 14:54

There's a list of plastics resistant to the conditions in a the (per-)chlorate cell in the page I linked to. Seems the guy has tested many different kinds (QUOTE: "Plastics that are suitable for the task are polyester, polypropylene, polyethylene, teflon, ployvinylchloride (PVC) and polystyrene (...and counting)."

.

Someone should invite that guy to SM, he seems really really clever. I'm reluctant to spread my email address myself...

[Edited on 2004-8-24 by axehandle]

Axehandle

MadHatter - 24-8-2004 at 15:11

I get the impression that the guy is a free-lancer, putting out his
info to all who care to read ! I've found other sites related to rocketry
where the writer even included a relatively cheap source for KNO3 !
Now if someone could give us MAD SCIENTISTs a comparable
source on cheap NH4ClO4, I'd be delighted !

axehandle - 24-8-2004 at 15:16

Well, you can order 8kg for 2100 SEK (+ VAT, totalling in at approx €252) from a Swedish mail order company I know, but that hardly qualifies as "cheap"...

NH4ClO4

MadHatter - 24-8-2004 at 20:23

Definitely not cheap so I think I'll just keep making my own.
Thanks for the info anyway !

Esplosivo - 25-8-2004 at 02:21

I don't suppose that the wearing out of the PbO2 electrodes would be a big problem. I read the stated amount of lead 'lost' form the electrode but currently I forgot hw much it was. Anyway, one can always electroplate the electrode with more PbO2 after a certain number of runs. The Pb 'dissolved' in the solution would form either the chloride or the sulphate, bot of which are sparingly soluble and can therefore be filtered out before precipitating the perchlorate.

Jome - 11-9-2004 at 15:55

Why not make NH4ClO4 if it's needed? If you manage to go all through the chloride-->chlorate-->Perchlorate process without adding K-ions you should be able to precipate NH4ClO4 by adding f.ex NH4Cl and lower the temperature of the solution down to like 0 degrees centigrade.

NH4ClO4

MadHatter - 11-9-2004 at 16:26

Jome, there is a danger in making NH4ClO4 when using perchlorate
from your own electrolysis. You have to make DAMN sure that there is little
or no residual chlorate. If NH4ClO3 is produced in any appreciable amount
you risk the chance of detonation of the entire mix given the instability of
that substance. The indigo carmine test that I use is adequate for the
detections of chlorates.

axehandle - 16-9-2004 at 21:04

Can anyone think of a suitable, easily available piece of plastic to use as the substrate for the anode? I've been unable to find PVC rod (or any plastic rod actually) and the best I've come up with is a piece of PE (I think) from one of those things you cut vegetables on in the kitchen (word eludes me but you probably get the idea) -- problem with that solution is that the plastic is too soft (wouldn't want the PbO2 layer on the anode to break).

Another idea would be a piece of very thin plastic pipe plated on the outside..... one of those pipes for electrical installations would work I guess but I've no idea what type of plastic they're made of and whether it's soluble in THF...

Round shape would be good, square shape workable if plated on one side I suppose...

The surface area I'm after is probably something like... well... say 50 square centimeters or so-so, no problem if too much since the anode's depth in the perchlorate cell is easy enough to adjust.

I hate not having any good ideas...

BTW, about making NH4ClO4: It can be done with NH4NO3 as well as NH4Cl --- good good, finally some use for all the ammonium nitrate I've stashed away!

Also, anyone having any objections to my plan of using a DC arc welding transformer (or AC one with humongous full bridge rectifier) to power my soon-to-be perchlorate cell?

Shit, I seem to have pulled an all-nighter. I'm too old for this... time for bed.

[Edited on 2004-9-17 by axehandle]

Esplosivo - 16-9-2004 at 23:39

An idea which sprang out of anything was to use formica, the one used for covering table-tops. Different varieties exist, some even colourless (avoiding unneccessary impurities). I don't know about its solubilty in solvents and its capablity to resist chemical attack though. According to my own experience it is fairly stable though, resisting most dilute acids (for example 45% H2SO4). Hope this helps.

Edit: Typo

[Edited on 17-9-2004 by Esplosivo]

axehandle - 17-9-2004 at 07:23

Good idea! It also gave me another: Acrylic, Plexiglass! Perhaps even polycarbonate (although that beast might not be THF soluble)...

What IS formica and what might it otherwise be called in construction stores?

Esplosivo - 17-9-2004 at 07:38

Formica is a condensation polymer formed by reacting methanal (formaldehyde) with urea (carbamide). Where I live it is usually known as formica. It comes in sheets usually. Hope this site can help you understand what formica is:
http://www.formica-europe.com/index.cfm?Fuseaction=product.d...

As you can see the site is European, so using the mentioned brand names you could propably find it in stores.

What is plexiglass exactly? Is it also knwn as perspex, the methylmethacrylate polymer?

axehandle - 17-9-2004 at 10:54

Yes, plexiglass is polymethyl methacrylate (PMMA) or polymethyl-2-methylpropanoate.

neutrino - 17-9-2004 at 13:12

If you don't have any luck finding suitably sized plexiglass, many chem and bio suppliers sell plexiglass petri dishes pretty cheap, in many different sizes.

axehandle - 17-9-2004 at 13:41

Oh, plexiglass I can find easily, but not until tomorrow

... thanks for the idea though.

Gonna get 8mm thick sheet, should be sturdy enough...

I see that it's soluble in acetone, even! No need to waste the little THF I have!

I intend to test plating several different sorts of plastic once I've gotten the immersion heater for my plating tank (also to be bought tomorrow...). Titanium plate for the cathode(s) I already have...

[Edited on 2004-9-17 by axehandle]

rikkitikkitavi - 18-9-2004 at 07:34

axehandle, formica is also known as the polymer used in "perstorpsplattan".

have you considered using epoxy? Epoxy mixes well with fillers (like PbO2 or carbon) and is quite chemical inert.

/rickard

Axehandle

MadHatter - 18-9-2004 at 09:44

Axehandle, using an arc welder for your cell shouldn't be a problem as
long as the cell is big enough. The only problem I could think of is if
your arc welder has a limitation on the time it can be run. I use a battery
charger rated at 6 volts and 15 amps for my cell. It does a great job !
I stress the time factor because the chloride has to be converted into
chlorate at 1st. I don't know if this is a problem for an arc welder,
but I can tell you it's not a problem for a battery charger or a power
supply for a computer. I'd say go ahead. The worst that can happen
is that the arc welder will probably trip an internal breaker if the current
gets too high.

axehandle - 18-9-2004 at 11:08

Hmm, that's a point I've given some thought actually --- I don't know if a welding transformer can cope with "continous" running for long; I would suspect that those that can cope with it are not the cheapest kind.

Anyone know or have a pointer?

MadHatter, do you have data as regards to your cell volume and your anode area?

Also, a question for those more versed in electronics than me: Are there any caveats to connecting 2 or more power supplies in parallell to the cell? (if this works ATX PSUs can be used...)

Specs

MadHatter - 18-9-2004 at 13:37

Cell volume is just under 6L by the measuring standards you're using.
At 15 amps the current density on a 3/8 inch diameter gouging rod is
1.07 amps per square centimeter for a 12 inch rod assuming that all of
the rod(I WISH !) was submerged into the brine. I can't be 100%
sure on this because that's the initial current until the rod starts to
deteriorate and of course the current rises as the rod gets smaller.

That's for the anode. I use a gouging rod for the cathode also. It
doesn't deteriorate over time so I guess that I have to say it's static.

Dichromates are often used to protect the cathode if it contains iron -
not a problem for carbon. I still like to use NaF to increase the efficiency
of the cell and here's an article that may be of interest:

United States Patent No. 3,493,478.

Handady V.K. Udupa, Srinivasa Sampath, Kapisthalam C.

Feb. 3, 1970

------------------------------------------------------------------------

Electrolythic preparation of perchlorates

------------------------------------------------------------------------

Abstract of the disclosure

Sodium perchlorate is prepared electrolytically from sodium chloride
solutions in one step by passing a direct current through the solution ,
in the presence of sodium fluoride. A mild steel cathode and a lead
dioxide anode are satisfactory.

This invention relates to the electroltic preparation of perchlorates
directly from sodium chloride using lead dioxide anode.
Hitherto it has been the practice to employ a two stage process for the
production of perchlorates from chlorides , the first stage being the
oxidation of chloride to chlorate using graphite, magnetite or lead
dioxide anodes and the second stage consisting of the oxidation of
chlorate to perchlorate, using platinum or lead dioxide anodes. This
conventional process has various drawbacks, such as:
(i) that in between the two stages the solutions have to be processed to
isolate the chlorate and recover the unconverted chloride:
(ii) that graphite gets desintegrated to a considerable extent and
magnetite to a lesser extent when used in the production of chlorates and
(iii) that there is an inevitable loss of platinum due to corrosion in
the perchlorate cell.
With a view to avoiding the intermediate step of the processing of the
liquor after the said first stage of the conventional process, it has
been proposed that the effluent from the chlorate cell should be treated
under different electrolytic conditions from thoses in which the sodium
chloride solution was treated in the chlorate cell during the first
stage of the process. But this proposed process also is a two stage
process and the processing of the effluent from the chlorate cell
introduces complications in the method.
This invention has for its main object an improved method which will
obviate the drawbacks of known methods, and whereby the perchlorates may
be prepared directly from sodium chloride in a single step of
electrolytic oxidation, the conditions of electrolysis being maintained
constant at predetermined levels throughout the period. Another object
of this invention is to avoid the use of graphite, magnetite or platinum
as the anode. With these and other objects in view , this invention
broadly consists of a process of preparing sodium perchlorate directly
from sodium chloride in a single step of electrolytic oxidation, which
consists in passing a direct currint through a bath of sodium chloride
solution containing fluoride ions.

The improved process according to this invention may be carried out into
practice under the following conditions:
(i) The said fluoride ions may be provided by adding sodium fluoride ou
hydrogen fluoride to the bath.
(ii) About 0.5 to 5 grams per liter of sodium fluoride may be added; but
about 2g/L is ok.
(iii) The electrolytic oxidation may be carried out in a cell having a
stainless steel cathode and a lead dioxide anode.Br> (iv) The said anode
may consist of a massive lead dioxide or a GSLD.
(v) The current density may be in range 5 to 40 amps per square decimeter.
(vi) The electrolyte oxidation may be carried out at a temperature of 30
to 60 C.
(vii) The process may be carried until all the chloride is converted
into perchlorate, the conditions being maintained constant at
predetermined levels throughout the process.
The following Table 1. gives the particulars of three different examples
illustrating the invention.

TABLE I

EXAMPLE 1 2 3
Concentration of electrolite (initial) g/L NaCl 290.8 291 308.1
Sodium fluoride g/L 2 2 2
Anode GSDL GSDL GSDL
Cathode SS SS SS
Current density (amps /dm^2) 10 25 19
Current concentration (amp/L) 18.75 25 10
Temperature 40 40 45
Cell voltage ( volts) 3.0 to 3.9 3.7 to 4.5 3.9 to 4.5
Current efficiency % 52.2 53.2 57.5
Energy consumption (kwh/kg of NaClO4) 13.3 13.9 13.2
Current passed Amps 15 20 800
Duration (hrs) 105 78 223
Quantity of NaClO4 present in solution (gms) 544 546 61KG

___________________________________________________________________________________________
Table II shows other benificeal effects of using NaF.

Table II

Experimental conditions Without NaF With NaF
Anode GSDL GSDL
Cathode SS SS
Anode current density (amps / dm squared) 20 20
Current concentration (amp/L) 25 25
Temperature C. 3.5 TO 3.8 3.5 TO 4.0
Current efficienct % (with ref. to NaClO4 formed) 39.5 53.4
Energy consumption (kwh/kg of NaCl04) 16.2 12.3

Snip of most of the text repeating the claims above except:
Claim (3): Current density is in the range 5 to 40 Amps per dm^2.
Claim (4): Temperature is in the range 30 to 60 C.

Other patents sited:
2,813,825 11/1957 Miller et al
2,840,519 6/1958 Stern et al
2,872,405 2/1959 Miller et al
3,020,124 2/1962 Bravo et al

Now you know why I LOVE using NaF in my perchlorate cells ! It seems
that potassium persulphate can be used with a similar effect.

I realize that this is for NaClO4 but getting the less soluble KClO4 is
easy with KCl given the fact that KClO4 will precipitate out of solution
very easily.

Solubility of KClO4: .75 gr @ 0 C, 21.8 gr @ 100 C according to CRC
52nd Edition(1971-1972).

Sorry for the long post but I hope this helps you in some way.

PbO2 electrodes

gilbert pinkston - 22-9-2004 at 18:10

do it the usual way shone on web pages
use cheap welding rods
they last from one to more days
save the broken pieces of PbO2
when you get enough put them in a fiber type window screen in the shape of a tube (not metal) put a new annode in top down in the pieces for electrical contact
put this in a chlorate solution but don't let the new annode touch the solution just the pieces
takes some maintanence but worked for me
went through one pack of rods but made about 100 pounds of NaClO4
lotta trouble just depends on how bad you want it
takes time
solution would get thick as mud from failed annodes but it all settles out to perfecty clear solution
keep adding NaClO3 untill crystals start to form
let cool
O4 crystals are thin flat and look like an enlongated diamond
they come out first
cleaning the electrode and putting it back in the plating solution long enough makes a big solid monster of an electrde
get rid of ALL ClO3 with HCl OUTSIDE away from civilization
don't even think you have got it all until you use indigo test to make sure

axehandle - 23-9-2004 at 09:39

OK, going to update this as I go... to collect my thoughts in one place if nothing else...

I've prepared a plating tank equipped with a stirrer (submerged aquarium water pump), an alcohol thermometer and a dimmer controlled 300W immersion heater.

I've filled the tank with 400g of PbAc2 dissolved in 2.5 liters of 6% HAc. This equals a concentration of 0.5mol PbAc2 / litre HAc.

I'm waiting for the electrolyte to reach 55 degrees C, then I'm going to try plating a piece of plastic I've previously coated with solid PbO2 powder using PVC glue (THF).

The plastic is a floppy bay cover from an ATX tower I had in a box --- I haven't measured its dimensions yet.

Should be possible to keep a fairly constant temperature once I've determined the proper dimmer setting...

I'm going to use 5V from an ATX PSU, with a lead cathode as suggested.

50 degrees, lots of bubbles in the liquid... have to wait until it clears up before mounting the substrate...

EDIT1: Here we go, started plating... I decided to forgo making a lead cathode and go with stainless steel instead. The cathode has about twice as large area as the substrate. I've placed them 80mm apart and the temperature of the plating tank is 40C and rising... this is exciting...

[Edited on 2004-9-23 by axehandle]

KClO4

MadHatter - 23-9-2004 at 17:36

gilbert pinkston, I've already made plenty of potassium perchlorate without
problems. As for indigo carmine, I have enough of that for a long time. Found
50 grams on eBay for $25. Not bad considering the higher prices I've seen
elsewhere on the net. My last batch of KClO4 was about 8 LBS. Very nice,
flat rhombic crystals in contrast to the KClO3's cactus needles which are
produced 1st during the electrolysis. BTW, I should have mentioned in 1 of
the earlier posts that the indigo carmine test can detect chlorates down
to 1 ppm. The test is sensitive enough to ensure that there shouldn't be
any problems when making NH4ClO4.

axehandle - 24-9-2004 at 00:59

Hmm, half of the electrode plated alright. I'll try making another with a more even (and thicker) layer of glued-on PbO2.

Looking good...

EDIT: Closer inspection revealed that the plating was OK in spots, mostly near the connection --- seems the main obstacle is getting the initial PbO2 layer conductive enough to carry the plating current. Next I'll try mixing graphite + PbO2 with PVC glue and smear that on the next substrate... but now I'm going away for the weekend so it will have to wait. I'm very optimistic though.

[Edited on 2004-9-24 by axehandle]

Some developments...

axehandle - 1-10-2004 at 11:07

Thought I should mention something of what I'm trying right now... I suppose many have read US patent 4008144 with the ceramic substrate PbO2 anode manufacturing process.

I decided to give it a go.

I made 4 substrates of clay, 3 of them cylindrical rods approximately 15mm x 200mm in size, the 4th a rectangular plate approximately 5mm x 150mm x 40mm. These I fired in my electrical kiln last night
(burning out the heating coil after 4 hours BTW --- which is horrible considering I have to wind a new one (gives you blisters and is boring) -- not important though but worth complaining about).

I've only begun processing 2 of the substrates; the plate and one of the cylinders; but here are my observations:

The substrates were soaked in a 52 degrees C, 0.5 mol/dm3 aqueous solution of Pb(Ac)2 (I dumped them in my plating bath, don't want to poison more glassware than necessary) for 1 hour.

Then they were dried in a 120 degrees C oven for approx. 1.5 hours.

Then I dumped them is a lukewarm saturated (at least I think so, there is undissolved stuff in the bottom of the jar) solution of Ca(OCl)2. This solution is supposed to be basified with a hydroxide for this to work but I reckoned the hypochlorite would be contaminated enough with Ca(OH)2 for me to avoid having to use OTS NaOH (contains sodium stearate and shit).

The substrates immediately turned light brown. I let them sit in the oxidizing solution for 2 hours, then I dumped them in warm tap water to wash them.

This is as far as I've got. I intend to let them sit in the washing bath for a total of 2 hours, them I'm going to dry them at 100 degrees C and repeat the process, as many times as necessary to get a good conductive layer of PbO2 for the electroplating to work -- probably nicely indicated by the "brownness" of the substrates.

More info coming as things happen...

axehandle - 2-10-2004 at 03:59

The process seems to works admirably -- I've finished 2 passes with all 4 substrates, and they get much "browner" with each pass. Stupid of me not to leave one of them unprocessed for color comparison though.

The question of how to make the plating connection arises. The obvious way would be a few turns of Ag wire around the end, if I had any Ag wire lying around. Blah. I suppose copper will have to do.

2 more passes on 2 of the substrates, 4 more on the other 2, then I'll try plating and record my observations.

Anyone knows whether a cheapo multimeter will allow current to pass through even when it's turned off? (I want to measure the plating current during the entire operation; simply including the multimeter in the circuit would be easiest.)

axehandle - 2-10-2004 at 11:29

Ooo-kay, here goes..... I've submerged the better part of one of the rods in the plating solution, which is heating up now (I'm gonna plate at 50 degrees C)... I'm using 3 SS cathodes surrounding the rod as plating cathodes.

The connection to the substrate is simply a strip of Al foil wound around the top...

Plating current is currently 85 microamps (at 5V) and rising... looking good.

EDIT: couple of minutes later: Has jumped to 106 microamps... should increase over time as the voids in the ceramic are filled with deposited PbO2.

EDIT2: I don't know how much time has passed --- 2 hours? Plating current was 450 microamps, I've turned the substrate upside down now, the part that was previously submerged should conduct much better now and indeed it DOES! 1.39mA and rising!

Painful having to plate half the electrode at a time, but if it works this anode should last forever..

[Edited on 2004-10-2 by axehandle]

axehandle - 3-10-2004 at 07:14

No, no, no. This is much too slow, I don't fancy plating for a week.

I'll get a much more porous clay tomorrow and start over. The clay I used was probably too fine-grained.

In the meanwhile, I'm going to try a plastic substrate again. Right now dissolving PMMA in acetone, gonna mix with PbO2 and cover a strip of PMMA. Observations coming.

[Edited on 2004-10-3 by axehandle]

axehandle - 3-10-2004 at 13:50

Aaah, yes yes yes! This works much better! Plating current is 0.1A.

What I did was make a paste comprised of plexiglass drill shavings dissolved in acetone (dissolved in about 30 minutes with intermittent stirring) mixed with powdered PbO2. Don't have any exact recipe for the paste, it's probably not critical...

The paste I smeared on one side of a piece of plexiglass, then I pressed the plate upside down in more powdered PbO2, then I forcibly evaporated the acetone for 2 hours in a 75 degrees C oven.

The conductivity of the pasted layer seems very good, my multimeter gave me something like 1k as compared with 4 orders of magnitude higher for the ceramic substrate I tried plating yesterday...

Anyways, there are some pictures in http://species8472.dyndns.org/pbo2/pics/PMMA/
in case anyone wants to take a sneak peek...

PbO2

MadHatter - 3-10-2004 at 14:05

Mixing some PbO2 in the paste probably helped quite a bit ! It should
ensure longer conductivity even if the coating starts to deteriorate. My last
PbO2 rod consisted of layers of PbO2 held onto PVC by plumbers
cement. The rod did deteriorate, but not nearly as fast as the
gouging rods. Probably due to the plumbers cement. On the bright
side, I was able to recover most of the PbO2 that had fallen off.

axehandle - 3-10-2004 at 14:17

Yes! Yes! Hooray! Victory at last!! I just checked the half of the substrate I plated at 0.1A for an hour, and it's covered with shiny blackish electroplated PbO2!!! I'm now plating the other half... Once that's done it should only be a matter of deciding how thick a layer of PbO2 I should aim at...

Behold, and be impressed!

axehandle - 3-10-2004 at 15:48

Right now thickening the layer even more by additional electroplating...

With a couple of strips of Al foil wound around both end of the anode, my multimeter gave me... tadaaa: Negligible resistance! Even the "connectivity beep" test beeped.

Ooooh, can't wait until I get a big bucket and a few kg of NaCl tomorrow --- perchlorate cell, here I come!

Oh, and BTW the substrate dimensions are 40x250x8mm.

PMMA_anode1.jpg - 29kB

Anodes

MadHatter - 3-10-2004 at 17:41

ROCK N' ROLL ! With all of the hard work you've put into your anode,
you're very deserving of a HUGE quantity of perchlorate ! I wish you
great success ! Be sure to let us know how it works out.

When you're electrolysing, chlorates will be the predominant compound
at least in the 1st few days. Easy to spot - nice thin cactus
needle-like crystals will form. Make sure you add enough water to
dissolve them. What you're looking for is the rhombic crystals of
perchlorate.

Tip: Keep your brine to no more than 10% chloride by weight to
start out with. According to Wouter, perchlorate production
doesn't begin until the chloride content is 10% or less by weight.
From personal experience, IMHO, Wouter hit the nail on the head !

BTW, your picture is impressive ! Check out your U2U later on.

[Edited on 4-10-2004 by MadHatter]

[Edited on 4-10-2004 by MadHatter]

A couple of observations

axehandle - 4-10-2004 at 17:31

that I've made while electroplating PbO2 on top of "glued-on" PbO2 are:

It can be so slow that you'd think is doesn't work. Raising the voltage helped for me, going from 5V to 12V *tripled* the current.
Maintaining the connection from the power supply to the substrate is tricky as it's near impossible to keep fumes from the heated fluid in the plating tank away from it -- I noted that the Al foil I used "stuck" to the PbO2 layer on the substrate, leaving a residue that scared me but which proved easily removed by the HAc in the plating bath. Making sure the "connection spot" on the substrate is completely dry prior to wrapping it in foil and wrapping it tightly to avoid water vapor coming between the foil and the PbO2 layer helps as well. Using another metal as the connector would probably be better -- Au, Ag or Pt perhaps...
Even when plating at 12V, the operation WILL take an enormous amount of time: Getting the topmost 50mm of the substrate satisfactory thickly plated to serve as the connection for plating the rest took me upward of 6 hours! I suspect plating the rest will take even longer.
Keeping the plating bath heated makes a BIG (non-linear) difference with regard to the current. I've kept the temperature at between 50 and 55 degrees C, higher would probably be better but I don't want to boil the stirring pump that's submerged in the tank.
For the next anode (I'm going to make a bunch to have as spares, also planning to give away a couple) I'll definitely add graphite to the acetone/plexiglass glue. The conductivity is everything!
Electroplated PbO2 looks very different from glued-on PbO2. The former looks like shiny black metal, the latter like a dull, non-shiny brown. However, they look just the same when wet! This means that to see if the plating has actually worked, the anode has to be washed and dried.

[Edited on 2004-10-5 by axehandle]

rikkitikkitavi - 5-10-2004 at 09:21

is you newly plated PbO2 hard and adhering or is it more like powder that has been clad into place?

good work!

/rickard

axehandle - 5-10-2004 at 09:44

Quote:

is you newly plated PbO2 hard and adhering or is it more like powder that has been clad into place?

It's hard and glossy and seems to adhere very well. It looks a bit like shiny black rock. Lightly scraping one of my multimeter probes along it felt like scraping unglazed porcelain and made a similar sound. I'm not going to risk smashing the very tediously obtained layer performing any tensile strength tests though...

Quote:

good work!

Thanks.

[Edited on 2004-10-5 by axehandle]

rikkitikkitavi - 5-10-2004 at 13:14

no, we dont want you to risk anything

I was thinking about wether it could be considered a "robust" electrode that would survive many hours in a plating bath.

but it sure looks like it. A much more simple solution to the PbO2 electrode compared to
what otherwise is seen on the ´net.

I wouldnt worry to much about the Al. Some PbAc2 could splash onto it and therefore some Pb deposit, but any Al in solution will of course stay there. Just watch out with the pH so that Al(OH)3 doesnt preciptate.
I dont remember exact pH but usually around 6-8 if I remember it correctly.
Al(OH)3 preciptate will flocculate and probably mess upp everything.

/rickard

[Edited on 5-10-2004 by rikkitikkitavi]

Doing final plating sequence!

axehandle - 6-10-2004 at 16:55

I've obtained a good looking shiny PbO2 layer over the entire anode. I've done it by repeatedly plating 1/2 the anode at a time with the connection made from wrapping Al foil around half the anode's length, tightly wound tight with cotton string.

Plate, wash, dry, turn, wrap foil+string, plate, repeat (ad nauseam).

I must admit I was a bit nervous about the conductivity up until now. Not anymore.

For the final round I've wound many turns of ordinary stripped copper wiring around half of the anode, with 40mm of the other end submerged in the plating solution. Those 40mm will be the "connection area" when the anode is used in the perchlorate cell. Once I deem the layer in that area thick enough, I'll plate the other 210mm of the anode. That part will be submerged in the brine in the perchlorate cell.

The plating current never got higher than 100mA average during the "aluminum foil" steps. It's up at 2.2A with the copper wire! And rising! (Started with a cold tank.) Yes, precious, yes!

ARRGGHHHHH!!!!!

axehandle - 6-10-2004 at 17:12

Back to square 1.... damned thing caught fire.

Had to put it out with water. Fizzled like black powder. I suppose that's what I deserved for plating a combustible substrate (plexiglass) with an oxidizer (PbO2

...

I must admit I had not foreseen this possible scenario.

My theory is that the PbO2 coating heated up in some extra-thin spot and reached heat of initiation with the substrate. Fuck. Well, better now than in a finished perchlorate cell, I guess.

PbO2fire.jpg - 28kB

Saerynide - 7-10-2004 at 01:03

That sucks

But I agree - better it catch fire now than later

Great work nonetheless

Plastic

MadHatter - 7-10-2004 at 13:41

What about teflon ? Would this be less reactive than plexiglass ?
I've also been thinking about ordinary glass rods but I'm concerned
about the plating staying on. On Wouter's page there was also a
DSA anode using TiO2 and RuO2 on a Ti substrate. Like, Wouter,
I'd be interested in knowing if anybody has any experience with these.
Otherwise, it appears I'm stuck with gouging rods and PbO2.

neutrino - 7-10-2004 at 14:20

You'd have to melt the teflon to get it to retain the PbO2 and it would be hard to stick it to a solid object, but it would be interesting to try. Axe, how fast does material deposit on the electrodes in the plating bath? I'm wondering if it would be possible to build up a thick enough layer to simply remove it from a sheet of teflon as a self-supporting plate.

axehandle - 7-10-2004 at 15:08

Teflon might do the trick, but how would I make the PbO2 stick?

Quote:

Axe, how fast does material deposit on the electrodes in the plating bath? I'm wondering if it would be possible to build up a thick enough layer to simply remove it from a sheet of teflon as a self-supporting plate.

The speed of deposition depends on the current density when plating. Anything from hours to weeks depending on the power supply's voltage, it's power, the distance between the electrodes, the anode surface area, the temperature of the plating bath, the concentration of the Pb(Ac)2, the phase of the moon, etcetera

.

I like the removable substrate idea. Then again, PbO2 is very brittle. I think I'll go with a ceramic substrate for my next try. If the PMMA+PbO2 ignited from a measly 2.2A, there's no telling how many seconds it would last in a perchlorate cell running at 30A...

Now I only need to come up with a type of ceramic that's porous enough to allow a decent impregnation with PbO2 prior to plating. I'm not a potter. Ideas? A bench grinder grinding wheel would be excellent, but the shape is very wrong.

A plastic substrate anode has one advantage over a ceramic one: No corrosion at the connection from brine creeping up (which it undoubtedly will with a ceramic substrate). Though this, in theory, can be worked around by using silver as the connection metal in the finished perchlorate cell (corrosion products are conductive)...

One good thing came out of this: It opened my eyes to the fact that the PbO2 layer must be thick enough to avoid I2R heating. Wouldn't want the PbO2 to decompose from being too hot.

EDIT: I doubt it would be easy to obtain a DSA. I've previously looked for those but haven't found any... perhaps I looked in the wrong places. A DSA made from Ir or Pt on Ti would be sexy.

[Edited on 2004-10-7 by axehandle]

Twospoons - 7-10-2004 at 19:46

Terracotta is a nice porous ceramic. Maybe pieces of terracotta plant pot might work.

rikkitikkitavi - 8-10-2004 at 08:42

teflon cant be melted.
but it can be grounded into a fine powder which then is sintered.

It is common to use different types of fillers for some applications, like glasfiber

see attached link.
http://www.worcestercontrols.co.uk/worcsonline/3piece.html
if you look at the end of the table you see the "seat material" which is usually a teflon packing with or without fillers used for sealing the ball valve. It is manufactured with high tolerance

wether you can do this by mixing PbO2 with teflon powder I dont know.

edit: perhaps PVC can be used. It is not as inert as teflone, but is easier to come by and handle.

But the best is probably a completely inert substrate, or you have to remove the polymer after plating?
Could you not use a binder like CaSO4? This will be inert in the solution?

/rickard

[Edited on 8-10-2004 by rikkitikkitavi]

axehandle - 11-10-2004 at 10:15

I'm not too sure about this sintering process you mention. What temperature is typically needed?

I have a really whacky idea. What do you electrochemical gurus out there say to plating a pure Ag plate or mesh with PbO2? How would silver behave in an anode if it were to come into contact with the brine?

Any other metals I should consider (apart from impossible to get ones like tantalum)?

rikkitikkitavi - 12-10-2004 at 10:34

about sintering teflon and filler I dont know exactly how to do it. There is probably a lot of information in books about polymers or on the net, possibly patents aswell.

as for different metals, have you considered gold? A 10 um , 5*10 cm sheet is 0,05 cm3 or about 1 gr. 1 gr is around 15 €. If you are smart, you cover one half with paint or something insulating. then perhaps the sheet can be removed from the electrode and recovered. gold is also a very good conductor.

/rickard

axehandle - 18-10-2004 at 10:02

Gold sounds good if I could be sure it would work...

Today I'm going to try plating a platinized titanium mesh I have lying around with PbO2.

I also plan on trying to plate nickel. All platinum group metals supposedly make good substrates, so...

Otherwise, I have some ideas regarding palladium. Might be too costly though.

I have a novel idea regarding ceramic substrate anodes, and I see no reason why it wouldn't work with a plastic substrate: What about blending Ag powder into the clay prior to shaping and firing? It should be very conductive. The clay will have to be one firing under the melting point of Ag though.

[Edited on 2004-10-18 by axehandle]

BromicAcid - 18-10-2004 at 10:35

Soaking clay in strong acids can render it conductive. Rather then messing around with the silver idea.

Still though, I wish I knew a place where I could pick up some cheap tantalum for you

axehandle - 18-10-2004 at 11:45

Soaking the substrate in acid? Worth some investigation.... but the absorbed acid might contaminate the plating bath in some way...

I had partial success with the platinized titanium mesh. Most of it got IMMEDIATELY clad with PbO2 after just 15s in the plating bath! Some of it did not, however, and I'm 99% certain it's because cooking oil had gotten onto it in that spot (long story involving a filthy kitchen and stupidity). Apparently my boiling the mesh in detergent was insufficient, so I'm now soaking it in 30% ammonia.

The adhesion where the substrate was clean was VERY good, the PbO2 deposited thereon stayed even when rubbed roughly with a brush.

In worst case I'll have to buy a new platinized Ti mesh, but the only place I've found selling them charges an arm and a leg for them, and I'm not exactly loaded with cash, gggrrrrrrr.

More info coming soon...

TheBear - 19-10-2004 at 10:16

Why not using a solvent to clean the mesh? I recall chlorinated hydrocarbons being ideal for neutral fats, but excess of cheap acetone should suffice.

Result of plating the platinized Ti mesh

axehandle - 24-10-2004 at 11:12

As can be seen in the closeup I've attached, the results are both encouraging and discouraging. However, I'm hypothesizing that those... blank spots... were due to contamination of and/or damaging of the Pt layer. That mesh was treated very roughly by me before (getting tools thrown on top of it, etcetera...).

Still, I'm not sure if the result is encouraging enough to motivate me spending SEK700-ish on a new mesh.

PbO2clad_Pt-ized_Ti-mesh.jpg - 27kB

Mesh

MadHatter - 24-10-2004 at 15:49

Axehandle, The bald spots may be due to an imperfection during the production of the mesh.
I wouldn't worry about it as long as it works.

chemoleo - 24-10-2004 at 16:23

Nice - but waht I don't understand, why using PbO2-coated Pt(Ti), if Pt on its own is perfectly able to be used as an electrode for conversion of KCl --> KClO3?

Esplosivo - 24-10-2004 at 20:45

I would also like to ask, why use a platinized-titanium mesh where there could be other cheaper alternatives? I mean, does it really need to be a titanium mesh plated with Pt? Does anyone know of any other materials to which PbO2 adheres well and unreactive to Pb2+?

ClO4 Production

MadHatter - 24-10-2004 at 23:13

I posted here and at RS the procedure for making perchlorates using carbon(gouging)
rods as the anode. The problem with this method is that the rods have to be replaced
frequently. YES, you can make your perc that way but you need a good and cheap supply of
gouging rods but don't bitch when the electrolysis tears them up !

axehandle - 25-10-2004 at 07:14

Quote:

Nice - but waht I don't understand, why using PbO2-coated Pt(Ti), if Pt on its own is perfectly able to be used as an electrode for conversion of KCl --> KClO3?

Good question. Thing is, I read in several places that Pt makes as excellent substrate for electrodeposited PbO2, and I wanted to evaluate it first hand, to get a first hand account of it. Call it scientific curiosity or stupidity, your pick

.

Also, there's one reason: The Pt layer gets eroded if the chloride concentration drops below 10%. I doubt a puny micron-magnitude Pt layer could stand up long.

Quote:

I would also like to ask, why use a platinized-titanium mesh where there could be other cheaper alternatives? I mean, does it really need to be a titanium mesh plated with Pt? Does anyone know of any other materials to which PbO2 adheres well and unreactive to Pb2+?

First question: Already replied. Second question: That's something I'd also very much like to know, but noone seems to know. Remember that the substrate we're looking for must several very hard to meet criteria that I can think of:

Must be a decent electrical conductor.
PbO2 must adhere extremely well to it.
Corrosion products resulting from the brine must be electrically conductive AND must not dissolve in the brine, otherwise the PbO2 must be completely hermetically sealing around it. The latter I don't find realistically achieveable with my plating technique.
Again, the substrate must resist anodic oxidation OR the oxide layer must both not dissolve in the brine AND must adhere well to PbO2 as well!
Must hold up to weeks in a (per)chlorate cell, will all the chemical abuse that entails: Being half-boiled in an aqueous solution of Cl2, being bombarded with bubbles of O2, etcetera.

Not easy criteria to meet.

Idly speculating, the only ones that I'm fairly sure of worth investigating are Ni/Pt/Ir (platinum group metals, only Ni worth really investigating in solid form due to cost issues), Fe3O4 and perhaps a couple other metal oxides, and PbO2 itself. Feel free to speculate, I'm always eager for someone to relieve me by suggesting a probably obvious answer which I didn't think of...

Magnetite poses insane difficulties in melting and annealing it, otherwise I'd have tried it out a long time ago. Gold might work, but I can't find any references as to whether PbO2 adheres to it or whether it would be resistant to anodic oxidation.

Quote:

I posted here and at RS the procedure for making perchlorates using carbon(gouging)
rods as the anode. The problem with this method is that the rods have to be replaced
frequently. YES, you can make your perc that way but you need a good and cheap supply of gouging rods but don't bitch when the electrolysis tears them up !

Seen it. I might try it out (I know a somewhat cheap supplier of gouging rods) but not until persuing the holy grail... eh, mean PbO2 electrode, isn't fun anymore

neutrino - 25-10-2004 at 14:16

Would it be feasible to plate a sheet of copper with PbO2 and remove the copper afterward, leaving only a sheet of PbO2 behind?

Esplosivo - 25-10-2004 at 20:42

Quote:

Originally posted by neutrino
Would it be feasible to plate a sheet of copper with PbO2 and remove the copper afterward, leaving only a sheet of PbO2 behind?

How do you propose of doing that? Do you mean plating a Cu electrode and then dissolving the electrode in some acid or something? That would require very concentrated acids and I doubt that the fragile PbO2 would hold intact for long.

[Edited on 26-10-2004 by Esplosivo]

Hermes_Trismegistus - 25-10-2004 at 23:27

Quote:

Originally posted by neutrino
Would it be feasible to plate a sheet of copper with PbO2 and remove the copper afterward, leaving only a sheet of PbO2 behind?

if you could plate a sheet of copper with the lead oxide, why bother dissolving the copper out, why not just leave it in?

Oxydro - 26-10-2004 at 03:17

Wouldn't the copper reduce the plating as fast as it formed?

Edit: woops, never mind, bad morning!

[Edited on 26-10-2004 by Oxydro]

Esplosivo - 26-10-2004 at 05:27

Quote:

if you could plate a sheet of copper with the lead oxide, why bother dissolving the copper out, why not just leave it in?

That is what I was wondering about. It could be done. There is a probelm though. If the Cu is exposed then the chlorine dissolved in the solution would most probably react with the Cu contaminating the solution and eroding the electrodes.

Oxydro, I highly doubt any sort of rxn - remeber that Pb is more electropositive than Cu - this is why the rxn (CH3COO)2Cu with Pb occurs in the first place.

[Edited on 26-10-2004 by Esplosivo]

neutrino - 27-10-2004 at 13:30

Here’s an idea: make some PbO2 powder, pack it down into the bottom of the plating vessel, attach an electrode, and let it run for a while. You should eventually get a plate of PbO2 with some powder on the bottom that should be easy to scrape off and reuse.

Twospoons - 1-11-2004 at 14:07

Quote:

Oxydro, I highly doubt any sort of rxn - remeber that Pb is more electropositive than Cu - this is why the rxn (CH3COO)2Cu with Pb occurs in the first place.

But PbO2 is a good oxidiser, and this is precisely why finding a good substrate is so difficult. The reason Cu 2+ is added to the plating baths is so that it will be deposited on the cathode preferentially to the lead, maintaining the lead ions in solution so they can form PbO2 on the anode. I suspect a copper anode would dissolve rather rapidly

Esplosivo - 1-11-2004 at 14:54

Quote:

The reason Cu 2+ is added to the plating baths is so that it will be deposited on the cathode preferentially to the lead, maintaining the lead ions in solution so they can form PbO2 on the anode. I suspect a copper anode would dissolve rather rapidly

I still cannot see why you think that the copper anode would react with the PbO2. The only route for the anode to dissolve is, as I mentioned previously, due to the Cl2 formed.

Twospoons - 1-11-2004 at 16:09

I was referring to the plating process, rather than chlorate production, though if you read through http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/chlorate.html, including all the lovely references in the 'Further Reading' section, copper is metioned as being a particular no-no in the chlorate cell.

Can't remember where I saw the ref to PbO2 oxidising the substrate, but this is supposed to be one of the reasons it can be hard to maintain a good electrical connection to the anode in service.

Eclectic - 14-11-2004 at 15:21

A good binder for chemically reactive systems would be PVDF (Kynar) dissolved in acetone or N-methylpyrrolidone (from environmentally safe paint stripper). You wouldn't think a fluorocarbon would dissolve, but it does in those two solvents (and few others). It's also about as stiff as plexiglass and can be melt formed.

Cu

MadHatter - 15-11-2004 at 16:11

Esplosivo, good call on that last post. Cu gets torn up rapidly during electrolysis in a
chloride solution. In fact this is how the Cu plating on gouging rods is removed before
using them for chlorate/perchlorate production. When removing this plating, the brine rapidly turns a dark green color as the Cu plating is eroded.

Eclectic, thanks for the info on Kynar ! This is something I have to try when I make my
next test anodes.

[Edited on 16-11-2004 by MadHatter]

lead dioxide electrode with lead or lead alloy substrate

Battle - 7-4-2005 at 00:15

I am making very weak attempts at the eelctrodeposition of lead dioxide onto a lead alloy or pure lead substrate. Anyone have any insite? I have read every string, patent, discussion, argument, or forum on the web, and cannot find any information on this base material's use as a substrate. I know a battery is the same thing but I want to electrodeposit the lead dioxide onto the lead, and use it in a cell. Any suggestions?

Battle - 9-4-2005 at 17:26

looks like I stumped the croud! Does anyone have anything???????????

cyclonite4 - 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.

Battle - 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?

I will search the string.

Twospoons - 10-4-2005 at 13:56

From what I've read you want the Beta form, because of its higher conductivity.

Rosco Bodine - 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 .

Battle - 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?

Battle - 12-4-2005 at 01:11

Sorry! Chlorate

cyclonite4 - 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

Esplosivo - 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.

Battle - 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.

Battle - 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.

Esplosivo - 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]

Rosco Bodine - 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

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]

Gold

MadHatter - 12-4-2005 at 20:46

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 !

Esplosivo - 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

Any Successful PbO2 Anodes Here?

jpsmith123 - 12-7-2005 at 04:22

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/...

12AX7 - 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.

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

jpsmith123 - 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.

Tantalum Rod Substrate

jpsmith123 - 21-7-2005 at 07:27

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.

garage chemist - 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.

jpsmith123 - 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

neutrino - 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.

jpsmith123 - 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.

garage chemist - 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.

gilbert pinkston - 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

Pages: 1 2 3 .. 12