Sciencemadness Discussion Board

More on PbO2 electrodes

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hashashan - 17-1-2008 at 16:01

Well my cell finished his run, a bit late but its ok. Positive with MB test.
And then came the stage to destroy the chlorate ..... Never had problems with that but now god damn ..... just cant destroy them. The sulfite method doesn't work, I don't get the SO2 smell, get positive with the manganese sulfate and phosphoric acid test and really really positive with IC test(I wonder if anyone got negative with it )

I thought that maybe my problem is that the Mn test hits positive because of the persulfate added in the beginning ... anyone got ideas what to do?
the liquor is now flooded with HCl and Na sulfite already crystallized out of it.
Im desperate.... meanwhile started another run without the persulfate just to see what happens

@dann : it works like charm

[Edited on 18-1-2008 by hashashan]

12AX7 - 17-1-2008 at 16:39

If it's "loaded with acid", the chlorate is present as HClO3 (pH < 1 or so) and decomposing to Cl2, which should more than oxidize any sulfites present (at this pH, H2SO3). So if it doesn't smell like SO2 on further addition, that's weird, but if it also doesn't smell like Cl2 (assuming it is acidic enough), there's nothing to worry about.

Tim

dann2 - 17-1-2008 at 17:00

Hello,

I used a stirrer. The anode was really just a 'prerun' as I had no idea if LD would even stick to Mangetite. I did not even round the edges of the Ti as I had no idea if the Magnetite would form in the first place!
Magnetite is a bit of a pain in the ass to put onto Ti but it may make a rugged anode (may not!!)

Cheers,
Dann2.

dann2 - 17-1-2008 at 17:15

Quote:
Originally posted by dann2
Hello,

There is an artical here about the use of CTAB in plaitng baths.


Dann2


Hello,
I cannot find this article. Does anyone have it?

I remember reading it but for some reason or other it is not on my pc (or here either). Perpahs it was a top secret, self destruct file :o

I have Silicone Carbide. Would I be right in assuming it will not be attacked in a LD plating tank if used as the ceramic particles?

Cheers,
Dann2

[Edited on 18-1-2008 by dann2]

tentacles - 17-1-2008 at 17:45

I'm going to try making an ATO solution and put a couple coats of DTO over the Co spinel I put on a second piece of ti (the one I have been using to plate PbO2). After this I am going to try plating PbO2 over.

I put a few coats of (possibly?) Bi doped MnO2. 5% bismuth (as metal) onto Betty. I should really dunk that b*tch into some chlorate soon!

[Edited on 17-1-2008 by tentacles]

[Edited on 17-1-2008 by tentacles]

jpsmith123 - 17-1-2008 at 18:45

Dann2 are you talking about the article that has this paragraph:

The addition of different surface active agents to avoid pinholes has been described previously (13, 14, 25-27). In the course of the study on measurements of stress in electrodeposited lead dioxide(28), the authors found the addition of quaternary ammonium surfactant not only lowered the stress but also helped in obtaining a pore-free deposit on stationary graphite even at higher current densities(29) . An example of q.a.surfactant is Cetyl Trimethylammonium bromide also called Hexadecyltrimethylammonium Bromide. Use 2-3 grams per liter.

If so, it's here:
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

hashashan - 18-1-2008 at 08:52

But is there any reason that I get positive with the Mn phosphoric acid test? (that small amount of persulfate can differ?)

tentacles - 18-1-2008 at 10:11

hashashan: I had a similar problem with the liquor I ended up with after I ran that other LD anode. HCl and sulfites didn't seem to cause any reactions. Have you tried sugar + H2SO4 to test for chlorates?

dann2: CTAB, and there was another surfactant discussed somewhere, seems to be quite hard to find. I think JTBaker has it, for like $25/15g or something. I believe a few articles have mentioned using a nonpolar agricultural surfactant. I've been wanting to try the agri surfactant but the fertilizer shop doesn't have KNO3 in yet this year so I've been waiting. One problem with the sufactants is that they decompose over time in the plating tank, so the lifetime of the plating solution is somewhat limited. Still, there are ways that the lead could be recycled and the stress relieving effects are probably worth it.

[Edited on 18-1-2008 by tentacles]

hashashan - 18-1-2008 at 11:15

@ tentacles : not yet, I didn't dry the crystals yet. However that is a crappy test

dann2 - 18-1-2008 at 12:39

Hello,

Thankks for replies.
@Xenoid That is not the articlal. The artical goes into detail about the way CTAB is used up as LD is plated.
I just wanted it for completness. Have no idea how/where it dissapeared to.

I agree that adding Surfactant complicates things + price.

Dann2

tentacles - 18-1-2008 at 20:52

dann, Was that the article/patent where massive PbO2 was plated on niobium? I've been looking for that one in the time since I've read it, and I seem to recall some discussion about different surfactants. Igepal CO-880 or something, and a random agri nonpolar.

tentacles - 18-1-2008 at 20:52

dann, Was that the article/patent where massive PbO2 was plated on niobium? I've been looking for that one in the time since I've read it, and I seem to recall some discussion about different surfactants. Igepal CO-880 or something, and a random agri nonpolar.

dann2 - 19-1-2008 at 13:35

Hello,

Patent here for massive anode on Ta (if thats any use).
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...
(around middle of page)

Found it. Perhaps I may have never read the artical? only seen the reference:
https://article.pubs.nrc-cnrc.gc.ca/RPAS/RPViewDoc?issn=1480...
Consumption of Cetyl Trimethyl Ammonium Bromide (CTAB) during Electrodeposition of Lead Dioxide
Kapisthalam Chetlur Narasimham, Srinivasaraghavan Vasundara, Handady Venkatakrishna Udupa
Canadian Journal of Chemistry 53 pp 3327-3329


If you google ' lead dioxide ctab ' it will come up (and more).

Not really wanting to use CTAB just to read and perhaps learn something.

CTAB can be had on ebay.co.uk if anyone wants it.
The CTAB thing seem to be a whole religion if its own!!!!!!!
There is even a http://www.ctab.org.uk LOL
Applications are mouthwashes, losingers and antiseptics.

(and of course mad anode making)


@Hashashan
Did you try heating the solution when destroying Chlorate.

Dann2

[Edited on 19-1-2008 by dann2]

[Edited on 19-1-2008 by dann2]

hashashan - 19-1-2008 at 16:15

brought it to boiling .. and added all the sulfite to the boiling solution.
It did look like some reaction happened ... but yet I added tons of sulfite and still positive on the Mn test.

tentacles - 19-1-2008 at 21:19

I tried putting a couple coats of DTO on my Co Spinel coated strip today, the color is different now but I'm not entirely sure if it is a good coating. I also burned ou my damn heat gun, it'll be going back tommorow for a replacement. I almost set the anode up in the LD tank today but I'm still "recharging" it with lead and need to top off the water and filter out the copper and crap.

DerAlte - 19-1-2008 at 23:07

I am not sure on which of the half dozen threads this originated, but this one is as good as any to insert this....

A RETRACTION

Dann2 recently reminded me that I had promised to estimate whether the sample of “perchlorate” I claimed to have made by electrolysis on a carbon anode was, in fact, perchlorate. I have been lax in this due to attention to other business (to whit, the damned stock market). I have now performed what tests I can, and state:

To the best of my knowledge, perchlorates CANNOT be produced by the electrolysis of chlorates using carbon as an anode.

I had two samples, produced in 1995. One, labeled Chlorate (call it ‘C’ for short) was produced by electrolysis of saturated NaCl using a carbon anode. Part - the major part – was used by metathesis with KCl to produce KClO3.

The rest was then somewhat purified to get rid of as much NaCl as possible and subjected to further electrolysis, following a convincing sounding procedure “guaranteed” to produce perchlorate (found somewhere on the WWW). I added KCl to the electrolyte at this point order to precipitate any KClO4 so formed. I kept temperature much lower (by reducing current density and ohmic losses) than in the first case, since I assumed the process was a purely electrochemical ion oxidation conversion, with a different cell configuration (wide anode/cathode separation). A precipitate was formed.

This was bottled as ‘KClO4 (impure)’ – call it sample ‘P’. The only use I ever made of this was to demonstrate a few pyrotechnical reactions to my younger son. It seemed less reactive than the sample C.

When Dann called into question its composition, I sought methods available to me to determine this. I did not have conc. H2SO4 available nor Methylene Blue.

Chlorates react with any strong acid to give either Cl2 or ClO2 or a mixture; perchlorates do not, due to the kinetic barrier which accounts for their relatively poor oxidation performance, although the thermodynamics favor it over chlorates.

(1) A test of P with HCl gave off a gas that was either Cl2 or a mix with ClO2, by nose test. Conclusion: P contains Chlorate. This does not definitively say it does not contain perchlorate, however.

(2) Saturated solutions were made of both samples and a drop placed on a microscope slide and allowed to evaporate slowly. Crystallization was observed under X50 mag.

Result: C gave lozenge shaped crystals characteristic of KClO3, plus a few needles. Both of these forms are possible under the monoclinic classification of KClO3, where sides may be unequal but parallel and only one angle is a right angle.

P also gave the same shapes in the main – only one crystal was orthorhombic, where all angles are right angles, but sides unequal (unlike cubic) which is characteristic of KClO4. However, needles were also produced, and perchlorate can also be of the needle form (it is isomorphic with KMnO4, which tends to make needles in my experience).

Conclusion: If there was any perchlorate in P, it was a small amount.

(3) 1.000 g (+- 0.005g) of each of C and P were dissolved in 33.3 mL (+-0.3mL) water at RT – both dissolved. This shows that less than 70% was perchlorate. The solution was so chosen that pure chlorate would be just saturated at 0c. Both solutions were cooled for 3 hrs. in a water bath in a refrigerator to slow the ice melting. One or two small crystals were then seen floating in C; none in P. The P solution was somewhat turbid at the start and a fine white ppt. settled during cooling, but there was very little of it. Examination under magnification showed what looked like particles of a fibre. Non –crystalline.

The conclusion from test 3, (solubility) indicates that not more than 0.25g in solution (<25%) could possibly be perchlorate. Taking account of the common ion effect, even including activity coefficient (from CRC) reduces this to a maximum of 0.063 g (<6.3%).

Overall conclusion: if perchlorate was formed at all, it was probably less than 5%. I was merely oxidizing carbon! Moral: Don’t believe what you see on the web, however convincing. And do some tests, always…

You were right, Dann!

Regards,

Der Alte

Xenoid - 19-1-2008 at 23:22

@ DerAlte

Should have gone in the "Perchlorate manufacture (not) with Graphite thread ... :D

Try an aquarium shop for some 3% Methylene Blue, they use it for treating fish diseases, this would finish off your proof!

DerAlte - 19-1-2008 at 23:58

Yes, not with...

Have no use for perchlorate myself. It's rather boring, apart from pyrotechnics. However, your efforts to produce the MMO, etc, Anodes are very impressive.
Der Alte

dann2 - 20-1-2008 at 06:03

Hello,

@DetAlt It is good to put the 'Perchlorte from Graphite' thing to bed once and for all!


@Tentacles Did you drill lots of holes in the Ti . It is a very good (I think!) way to help the Lead Dioxide to stay in place.
What is you DTO recipe??
Hope it is <strike>not</strike> similar to the Diamond Shamrock patents!!!!!!!:P

Dann2

[Edited on 20-1-2008 by dann2]

chloric1 - 20-1-2008 at 07:01

Quote:
Originally posted by DerAlte
Yes, not with...

Have no use for perchlorate myself. It's rather boring, apart from pyrotechnics. However, your efforts to produce the MMO, etc, Anodes are very impressive.
Der Alte


Oh man perchorates boring?! You let me down man.:( Ammonium perchlorate is easily converted to perchloric acid for which metal perchlorates can be made. I had a nice nickel deposit from a nickel perchlorate solution I electroyzed with no buffers or additives.

Don't forget potassium perchlorate's role in Self-Propagated High Temperatures reactions. This was mostly researched by the Russians so finding english papers takes a little sleuthing work.

Perchlorate occupies roles that chlorate is unable to do to the inherent dangers of instability.

[Edited on 1/20/2008 by chloric1]

Substrates standing by, ATO on it's way.....

dann2 - 20-1-2008 at 09:54

Hello,

Some examples of drilled Ti substrates. Will be ATO'ing + LD'ing once I get my Sodium Potassium Tartrate for the Alpha LD plating bath.
Substrates in picture have yet to be etched. Will not be sand blasting as I don't have a sand blaster or access to one.

I wonder if you were to take a new clean wire brush and with the Ti on a firm bench, strike the Ti with the points of the wire on the brush a number of times. Would this rough up the surface like sand blasting would?



Some of these's substrates are very thin as they have been etched many times.

Dann2

tentacles - 20-1-2008 at 10:45

dann2: I'm attempting ATO using 95/5 solder, HCl + H2O2. The tin dissolved fine, left the characteristic antimony trioxide, added a splash of H2O2, and the reaction was VERY vigorous, like adding carbonate to strong acid. The color of the strip changed from the Co spinel shade of grey.

I wouldn't recommend using a wire brush, it could leave bits of steel or stainless embedded in your Ti. I did not drill my strip, although I suppose I still could. Problem is, my heat gun is down until I take it back to canadian tire, so I'm up a creek on plating it today if I do drill it.

One thing I have been wondering is, what would be an appropriate method to connect the power to the anode? I am planning on attempting to silver plate the end of the strip, see how that goes.

I've been prepping the LD tank today, going to concentrate it down to 1L (~500g/l PbO2) and give 'er a go.

12AX7 - 20-1-2008 at 11:29

I use an extra length of titanium strip and bolt a copper strap onto the end.

The wirebrush I have doesn't do much to titanium. It's hard shit!

Tim

hashashan - 20-1-2008 at 12:01

I just sanded with sand paper mine .... it works ok .. makes it shiny

dann2 - 20-1-2008 at 19:24

Hello,

Seems to be hugh differences in the hardness and corrosion resistance of Ti when you go from cp Grade 1 (Dann2 + Hashashan) to cp Grade 4 (Tim).
The Grade 1 (my stuff) etches easily in hot HCl and is quite soft.
Tim's stuff in semi indestructable.

Perhaps the stuff you have Tim has been processed in some way (heated?) and ours has not?

Perhaps the Grade you/I think we have is not correct.
I purchase mine on ebay as CP Grade one, but I cannot be 100% sure if that is what it is. The seller had no reason to tell me it was anything else.
Would it be possible that you have perhaps a grade that contains Palladium (0.015%) for extra corrosion resistance?

There is data here for Ti corrosion. They do not state grade so not much use. It is interesting to note that under 'Nitric + Hydrofluoric' they say "not recommended"?
The Nitric + Hydroflouric is what is used for cleaning stainless steel and is available in welding shops
Br seem to be good!
http://www.titaniumprocessingcenter.com/data.php

Also pdf on corrosion here:
http://www.timet.com/coresistframe.html



@Tentacles: With 5% Sb in your ATO I am going to have to 'think of England' while you are making the anode. :D

Dann2

[Edited on 21-1-2008 by dann2]

[Edited on 21-1-2008 by dann2]

[Edited on 21-1-2008 by dann2]

12AX7 - 20-1-2008 at 20:32

My stock is just as springy in current condition as it is annealed to orange heat.

It sands just fine, with wet SiC, but it also goes through a lot of sandpaper to get much progress. I might have a crappy brand of sand paper, but I don't feel it's unexpected given the nature of this material...

A glance reveals "strength increases with grade number" from CP1 to CP4. In fact, a perusal of MatWeb reveals: CP4 is specified as around 80ksi tensile yield, while CP1 is around 30. Likewise, Brinell hardness is specified as 250 vs. 120, respectively. CP1 seems to be the most pure grade. 6Al4V annealed is specified as 128ksi yield, hardness 334.

It's kind of hard to compare to steel, I'd have to guess CP1 is like mild steel, CP4 more like carbon steel, and 6Al4V more like alloy steel. But the thing about steel is, it can be annealed quite easily, and even the alloy steels end up softer than this stuff, when annealed. Titanium is springy when annealed, and it only gets worse with the higher grades. An awesome structural material for sure! Steel also can end up much harder, turning to glass in an intermediate step. I think titanium is like carbon or alloy steel at a moderate temper (spring temper, roughly). Soft enough to bend rather than break, but strong enough to be springy...and hard to work. There is one commonality: the purer alloys are softer!

Fleaker, I might want CP1 next time... :)

Tim

tentacles - 21-1-2008 at 12:45

I stopped plating the PbO2 today, just a few minutes ago. Hard to say exactly how adherent it is, but it is VERY smooth! I ended up adding more NaF dopant to my PbO2 tank, my dumb ass picked up the wrong bag - it was next to my bag of 325 silica. I don't think any more of it actually dissolved, as NaF isn't very soluble. There was probably already a saturated amount left in the plating solution after the last two sessions.

I can't find the camera right now, but this anode looks good, there are a few pinholes which should not matter too much if the DTO did a good job of sealing. I plated on about 1mm total, so about .5mm thick layer. I thought about plating on more, but I didn't really see the point of a massive layer.

It's entirely possible that the only way to get a pinhole free LD plating is with a surfactant, or perhaps even the right surfactant.

I'm not sure if I want to test this one in KClO3 or KCl.

dann2 - 21-1-2008 at 14:17

Hello,
Quote:
Originally posted by tentacles
..... my dumb ass picked up the wrong bag - .............


Your dumb ass has amazing manual dexterity!!!!!!!

Quote:
Originally posted by tentacles
..... there are a few pinholes which should not matter too much if the DTO did a good job of sealing. .............


My take on the Ti/DTO is that the function of the DTO is to stop the LD from Oxidizing the Ti, not to protect the Ti from the electrolyte. The Ti will protect itself from the electrolyte if it should come into contact with it by forming its protective Oxide coating.
If there are pinholes I suppose it may be possible for the electrolyte to travel along the Ti/DTO interface and ruin the anode that way, or perhaps travel along the DTO/LD interface and cause seperation.
I wonder if (it's remenisent of the graphite!) if you were to put your anode into a container of sealer of some sort and pull a vacuum and then cure. This would help put an end to any pin hole problems that may occur. Hopefully pin holes do not cause problems with this type of anode.
Only time will tell.

Perhaps KCl or NaClO3. If you use KClO3 the Perchlorate forming will encrust the anode (or so I believe).

Dann2

[Edited on 21-1-2008 by dann2]

tentacles - 21-1-2008 at 15:26

Well, in other news, I fumbled the ball, straight down onto the floor and a good portion of the LD cracked off (in sheets, interestingly). I did have time to do some resistance testing (and clean out my 4L beaker/cell) and this looks promising. If I can find the high res camera I will take pictures of the LD. From appearances, the pin holes DID NOT go all the way through the LD - they were only on the surface, no more than half way through. Most of the resistance points (measured from a SS screw in the top of the Ti strip) were well under 100 ohms.

I have since done a light sanding on the anode, baked on another 3 coats of ATO, wiped and am replating with LD at 20ma/cm2. I started out at 3.5A (~80ma/cm2) for 15 minutes to put a 'flash' plating of alpha PbO2 on there. It should be plated heavily enough by bedtime to take some pics. The previous attempt was done at about 9ma/cm2.

[Edited on 21-1-2008 by tentacles]

dann2 - 21-1-2008 at 16:02

Hello,


Oh no !!!!!!!!!

From my previous experience measuring the resistance of LD (the chemically deposited coats used to make ceramic conductive when making ceramic substrate LD Anodes) it can be difficult to come up with a accurate measurement.
The 100ohms seems very very high.
Use a resistance measuring device that sends a decent current through the LD that you are measuring. Take a battery + resistor + meter combination that sends a few milli Amps (as opposed to a few micro Amps with a modern meter) through the LD to measure the resistance.

Dann2

12AX7 - 21-1-2008 at 18:50

I'm reminded of something wholly useless I did.

I had a moist sample of PbO2 powder in a jar. On a whim, I measured its resistance. Oddly, it showed something absurd, like more than infinity, or a negative amount. Clearly, it's producing voltage. I switched over to DC and saw a volt or two. Probably the steel ground clip redoxing with the PbO2, and the brass probe acting as an inert connection.

Tim

tentacles - 22-1-2008 at 15:48

I got my thermocouple today, took some measurements. With no restriction on the end of my tube furnace, I get 14.2mV, corresponding to 350C in my CRC handbook. BUT this thermocouple reads 0mV at 20C(should be .79mV), so this may be as high as 360C (14.71mV). Restricted by placing a 1" piece of steel bar on top (leaving the tube to either side venting freely), the heat goes up to 16.8mV, ~410C.

I'm almost done recoating that Ti strip, will subject it to PbO2 plating hopefully tonight, I have to pick up a freezer (future kegerator) tonight though.

[Edited on 22-1-2008 by tentacles]

plating in layers

quest - 23-1-2008 at 07:58

I'm a little short of time for electroplating my PbO2 electrode.
I'm at home only for 2 days every week.
As far as I understood you can't plate for some time, let it rest for a week, and plate it some more. The layers won't adhere to each other.

So I thought maybe I can put the electrode in HNO3 or some other solution to make the outside layer active again.

Any ideas?

(plating for more than 2 days is unreachable for me)

dann2 - 23-1-2008 at 10:22

Hello,

At 20 or 40 mA per square cm you will build up quite a thickness (some mm's) in a day.
What thickness do you want?
Are you plating on a substrate or massive?
I dont know anything about making the outside layer more active again. It is not a good thing (as you said) to stop and start again.

Dann2

Twospoons - 23-1-2008 at 13:17

Maybe you could leave it with a tiny trickle of current - just enough to keep the plating going, not so much you need to babysit the plating bath.

tentacles - 23-1-2008 at 19:35

I got my keezer yesterday, and today I was working on it but I did take a break to slop on a 4th coat of DTO (so 4Co/4DTO/PbO2) and dunk this thing in the plating tank. I'm using low current again to try and replicate my first plating. I promised Xenoid I would weigh this one! And goddamn it, I DO NOT want to drop this one. I lose more potentially good anodes this way :/

The irony is that I again forgot to weigh the pre plating anode. My other anodes are very close to the same size (I can weigh them all and average the numbers).

Another question is, how thick of a PbO2 plating do we consider durable in an electrochemical sense? Does anyone know the (any) wear rates for PbO2?

[Edited on 23-1-2008 by tentacles]

tentacles - 24-1-2008 at 05:52

I checked on the anode today, the PbO2 bubbled and was peeling again. I have no idea why it's doing this, my best guess is my DTO solution is not working properly anymore. Maybe I'll try one with just Co spinel.

quest - 24-1-2008 at 09:51

Quote:
Originally posted by dann2
Hello,

At 20 or 40 mA per square cm you will build up quite a thickness (some mm's) in a day.
What thickness do you want?
Are you plating on a substrate or massive?
I dont know anything about making the outside layer more active again. It is not a good thing (as you said) to stop and start again.

Dann2


I'm going to try making masive anode like hashashan did, using hashashan's Ti plate. His anode took him 4.5 days of electrolysis, so I guess that 2 days will give me too thin anode. (This doesn't mean I won't try to run it for only 2 days anyway).

hashashan - 26-1-2008 at 01:15

Dude I'm giving you a smaller Ti strip because the big one is currently in use .. so As I'm thinking If you'll plate in a bit higher current density 2 days will be enough

dann2 - 27-1-2008 at 17:37

Hello Folks,
Anyone know any refs. for Lead Tartrate LD plating bath.
I have GB850380
and JES Feb 1958.
The current density used in GB850380 is very small at 1.1mA per square cm.
No mention of CD in JES 1958
Is this the norm?

Dann2

dann2 - 2-2-2008 at 16:48

Hello,

I eventually got around to LD plating.
I started with a Ti substrate that has had ATO applied to it about 2 months? ago. 5 coats ATO afaik.
A picture of the substrate is on the board somewhere, it is the substrate described as 'already ATO'ed'
A coating of Alpha Lead Dioxide was applied by using a Lead Tartrate bath. (I could not get Lead Plumbate bath to work for me as stated somewhere else)
The Lead Tartrate bath was made up from:<br>
<ul><li>100 grams Potassium Sodium Tartrate </li>
<li>50 grams Sodium Hydroxide</li>
<li>96 grams Lead Oxide (Litharge)</li><br>
Dissolved as listed into 2 liters of water. The bath was heated to 60C to dissolve all Litharge. Any Litharge that did not dissolve was then filterer (or decanted) off. The Litharge was ground with a pestle and mortar to get rid of the lumps that were in it.<br>
The actual bath size used for the anode plating was 600ml.
The bath was used at 70C with a current density on the anode of 1.2mA per square cm. Gentle stirring was used. The tank had to be topped up with water on a regular basis as the level dropped due to evaporation. Ti cathodes (two) were used. The ATO coated Ti was plated for 22 hours to give a thin coat of black Alpha LD. This coat, when viewed at 100X appeared as a mass of nodules not unlike looking at blackberries. The anode at this stage weighed 22 grams and was 3.0 to 3.1mm thick and 9.8cm (active area) long (other dimension not measured).<BR></UL>

Next a coating of Beta Lead Dioxide was applied using a Lead Nitrate bath made up of:
<UL><LI>450 grams Lead Nitrate</li>
<li>6 grams Copper Nitrate</li>
<li>Nitric acid to put pH to approx. one (a few mls)</li>
All dissolved in 1 liter of water<br>
The actual bath size used was 800ml. Plating current was a steady 315mA.
A current density of approx. 17mA per square cm on the ATO'ed Ti was used at the start. At the end of plating, due to the increased size of anode, the current density was 7.7mA per square cm. The temperature was 55C. Stirring was used with approx. 12 grams of Aluminium Oxide grit (abrasive grit, sieve size 300 to 400) added in order to keep any bubbles that formed on the anode sweeped off. </ul><br>
Stirring had to be vigorous enough to keep grit in suspension. Ti cathodes were used. Evaporation was not so much of a problem but some additions of water had to be made to keep the tank level constant. The anode was plated for 35 hours. A coating of Beta Lead Dioxide was obtained of thickness 1.5mm at top of anode and 0.95mm at the bottom. The thickness of the coating seems to change fairly abruptly where there were no holes in the substrate. A total of 31 grams of Beta Lead Dioxide was deposited.<br>
The coating had a rough but shimmering texture. When viewed under 100X, faults were visible but it is not known of they penetrate deep into the Lead Dioxide. The plating was not continued for long enough to totally fill in the drilled holes in the anode/substrate. The anode measured 10cm by 15mm (14mm at bottom) by 6.1mm (4.9mm at bottom). This give an estimated surface area of 40cm squared.<br><p>
The anode will be put to work in a (Per)Chlorate cell at a current density of 300mA per square cm (12 amps) where it will hopefully work for at least six months 24/7. :)<br><p>

Before using the above Lead Nitrate bath I tested it using a small piece of Graphite. I got a good, (perfect) coating to the naked eye. When viewed at 40X it was surprising how many pin holes (perfectly formed) there was in the coating.

Photo to follow.
Dann2

chloric1 - 2-2-2008 at 17:38

Well, the faults and pinholes are demostrative why the ATO or MMO interface needs to be sealed so the oxidizing electrolyte does not penetrate and passivate the Ti.

dann2 - 3-2-2008 at 20:33

Hello,

You may be right.
We/I hope that when the solution enters the inevidable pinholes it will just corrode/wear away the DTO (or Co Oxide) and then just passivate the Ti in the vincity of the pin hole. It will hopefully not travel between DTO (or Co Oxide or whatever interface is there) and Ti and passivate the whole surface. If it does do this, then this type of anode will fail for in the amateur world (in general) as most of us (me anyways) are not going to set up an LD plating process to give PERFECT coats of LD.
If people are willing to set up an elaborate LD plating process then there is nothing to stop the (horribly disappointing in the past) graphite substrate anode etc from succeeding. I for one will not be doing it. The Ti anode with DTO + LD is hopefully going to be 'pin hole tolerent'.
Maybe not. At the end of the day only time is going to tell.

DTO will stand up for quite some time in a Chlorate or Perchlorate cell on its own. Co Oxide is not too good (bad in fact) in a Perchlorate cell (as shown by Xenoid and others).

Dann2

dann2 - 5-2-2008 at 16:18

Hello,

Picture of my first attempt at a Diamond Shamrock/Alembic Ti + ATO + Alpha + Beta LD anode. (as described above).
Camera not great.
Still have to put it in a cell ...or should I just leave it on the shelf and claim total success????????????/

Cheers,
Dann2 (AKA The Diamond Shamrock Diva :cool:)

[Edited on 6-2-2008 by dann2]

[Edited on 20-2-2008 by dann2]

chloric1 - 5-2-2008 at 16:51

Hey there!

Nice anode! I would try this! What that? Yellow tape?

hashashan - 5-2-2008 at 23:50

definitly a materpiece :) a great LD coating.. very smooth... no bumps(how did you do that BTW?)

dann2 - 6-2-2008 at 17:33

Hello,

The yellow tape was on the substrate from another plating attempt. (Using Sodium Plumbate which was not successful). I just left it there. It is a good way to give a ' sudden' end to the Lead Dioxide. You keep your plating tank level somewhere on the tape (level will vary but keep it on the tape.) The Lead Dioxide will plate up against tape and you will not have a ragged edge.

@ Hashashan
There is a discription of how I made the anode a few posts up.
A picture of the substrate was posted in another thread.

All LD anodes usually look good. The test comes when they are used for a week/month/months.


Dann2

dann2 - 19-2-2008 at 16:46

Hello,

I wrote up an account of making Ti substrate LD Anode using ATO interface layer here.

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

or to go up one tier

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


Dann2

tentacles - 20-2-2008 at 11:28

I'm rather intrigued by dann's success using SnCl4 to make ATO coatings - I wonder if you couldn't dope with a different chloride as well? Maybe BiCl3? Or even diffusion dope by layering, with a very dilute solution of dopant baked between layers of SnO2.

I'm thinking about picking up some SnCl4 and some PbO from chemsavers over on ebay. They've got the Cl4 for reasonable (considering it's 500g).

dann, how long has that been running for so far? Any idea how the adhesion is with the alpha undercoat?

edit: Chemsavers has their own site as well, with lower prices.

[Edited on 20-2-2008 by tentacles]

chloric1 - 20-2-2008 at 15:03

Well dann2 I am quite pleased with your website. I must give you my thanks on your relentless pursuits. I still want to play with cobalt/mixed spinels and MnO2 anodes for chlorate making but I now know how I want to try perchlorates. Also, you should be able to make other things with LD anodes such as persulfates, bromates, etc. that woud be handy because you could make your own persulfate catalyst for producing perchlorates:P:D:P.

I used boiling oxalic acid etching on the Ti6Al4V alloy and it worked but not with hot HCl. Still might use these rods but I want to try higher grade alloys. I was unsure about using flat substrates but with some sanding and etching, the edges can be rounded enough to nullify any deposit problems.

Have you had any success with Stannic chloride that you made yourself? Or your successes based on purchased stannic chloride? It might not always be available on ebay in the future.

[Edited on 2/20/2008 by chloric1]

tentacles - 20-2-2008 at 17:09

chloric: dann has tried with homemade "SnCl4" and had poor results. I believe his successful ATO coatings have used purchased SnCl4(-5H2O?).

[Edited on 20-2-2008 by tentacles]

hashashan - 20-2-2008 at 20:37

as I know you cant make persulfates with PbO2 .... the sulfuric acid will destroy the anode

dann2 - 21-2-2008 at 16:08

Hello,

The anode has only been going for two days as I could not get around to setting it up.
Ti cathodes (4)
2.150 liters of Saturated NaCl
10 amps (250mA per square cm on anode)
Added NaF
I am stirring using a homemade magnetic stirrer made from power supply fan with HD magnet stuck to it. (works good but stirring bar making alot of noise)

I hope to titrate some of the solution every two days or so and track formation of Chlorate and then the destruction of Chlorate (Perchlorate forming) all the way to the 'end'. I will not be measuring Perchlorate or Chloride.
Will also track pH and temperature and voltage but the pH I suppose is the one of most interest.

Regarding the ATO undercoat. It was make with purchased SnCl4:5H2O (Laboratory reagent grade). 'Antimony Chloride' was made from ceramic grade Antimony Oxide.
All efforts that I made to get SnO2 coat from SnCl2 or 'homemade' SnCl4 were a failure.
Perhaps SnCl4 (anhydrous (liquid)) would do for making an undercoat. It appears in some of the patents for use as a bare Tin Oxide anode. SnCl4 (anhydrous) is not that hard to make (depends on what you call hard I guess), you need Tin and dry Chlorine gas.

The Alpha Lead Dioxide is more compatible with ATO, has better adhesion and deposits more smoothly so you will not get as many humps and bumps as you start to plate. It is good start for the Beta which is inclined to go 'humpy and bumpy' if you have sharp corners.

I am going to get a cheap sand blaster. Perhaps I will not get around to using it on an anode.




The original report of this type of anode in the amateur world is here, from 10 Febuary 2004:

http://www.sciencemadness.org/talk/viewthread.php?tid=1425&a...



Dann2

dann2 - 25-2-2008 at 16:08

Hello,

The cell running the Lead Dioxide anode sprang a leak today. The magnetic stirrer bar wore a hole in the bottom of the plexiglass container.
Luckely only 160ml leaked out (2 liter cell).
Started again is a shallower cell, no stirring needed. I have abandoned measureing Chlorate concentration all the way to the end as I had to add 500ml more salt solution for the new cell.
Will moniter my next cell. The ph of the current cell went to about 10.2 at the start and then down to 9.2 after about 3 days. Perchlorate had started to form.
This was a bit too soon. I think that since the cell was very tall and the magnetic stirrer was stopping every now and then, this caused a 'micro cell' (0.9 l)
to form at the top of the container. Its temperature was going to 72c as it was not mixing with the bottom half.

Dann 2

hashashan - 26-2-2008 at 21:35

Well I know I promised to post pics of my anode like half a year ago ... here they are.
I don't have pics of it not installed in the cell ... as soon as Ill disassemble this cell Ill post some raw pics also.





the white goo on the anode is the remains of the hot melt glue I used to stop it from forming in some places. and the mess on the top was once the silver connection, It was heavily eroded because of some leeking gasses or liquids

Also It is a bit smaller now, because a bit of it broke off.

[Edited on 27-2-2008 by hashashan]

[Edited on 27-2-2008 by hashashan]

dann2 - 27-2-2008 at 12:00

Hello Hashashan,

A cathode both sizes would be better. Since the andoe is not smooth its apparent area is much bigger that the measured area. So you current density may be less that you imagine. Then again since there is only a cathode on one side the current density on that side will be more that estimated. As clear as mud I guess.
Thanks for picks.

Dann2

hashashan - 27-2-2008 at 14:39

Id love to put one more cathode but I dont have any more Ti. and I dont want to mess up the liquor with anyhting

dann2 - 27-2-2008 at 17:54

Hello,

I titrated some samples that came from my cell (before it sprang a leak).
Over a 22.5 hour period the Chlorate concentration increased 29 grams in the cell.
Running at 10 amps this is a staggering (we waaaa) 20% CE. WTF
Similar results from other samples. I got an appprox. straight line graph (four samples + zero at start).

Current density is 250mA per square cm on anode.

I think me LD needs a smathering of Bi !?

Dann2

hashashan - 27-2-2008 at 23:37

How wouldyou dope in some Bi?
how about to dope some Ti inside, hoping for the conductive oxide?

dann2 - 28-2-2008 at 12:03

Hello,

US 4,101,390 and US 4,038,170 (similar patents) say that Bi will help wear rate of LD anode. Bi is also supposed to be good at making Perk. The patents say the advantage is in cold solutions (for reduced wear). May make no difference in warm, non-pH controlled Chlorate cells.
There may be more pats on Bi helping wear rated.

Regarding my low current efficiency. I wonder would it be the cathodes. I have read articles where they got very different CE when different cathodes were used. 20% is pathetic. I am using Ti.

Or perhaps a lower Current density may help.
Will have to do something about it.

Dann2

tentacles - 28-2-2008 at 17:00

dann, I looked back and don't see a mention of whether you used an efficiency additive; NaF or persulfate?

[Edited on 28-2-2008 by tentacles]

dann2 - 28-2-2008 at 17:51

Hello,
I used 2 grams per liter NaF (added at start).
I am going to try lowering the temp. by putting the cell into a container of water.
If that does not work I will lower Current density on anode.
I leave the cell for 24 hours after each change, take a sample and titrate. This is handy to do once you have your solutions made up.
Dann2

hashashan - 4-3-2008 at 04:23

Hi, I have a possible good wa to make a PbO2 anode.
Yesterday I went to a jewlery shop to buy some silver for a good contact and I found there something interesting, a Ti mesh. but not just a Ti mesh... it is a very fine mesh, looks just like fabric, very thin(the strands are thinner then human hair). The mesh is about 3mm diameter sleeve.
So I thought, why not put that sleeve on some sort of substrate and deposit a layer of PbO2 on it.
It is seems like a cheap and reliable method.

There is a problem, what would be the best substrate? my thoughts are :

some sort of plastic :
ADVANTAGES: cheap, easy to find, easy to handle, the liquer wotn harm it.
DISADVANTAGES : If there will be a bad connection that will cause heat, the plastic will melt and might even catch fire. and it wont conduct heat out

Glass :
ADVANTAGES : quite cheap, the liquer wont harm it, neither will it melt nor catch fire upon heating.
DISADVANTAGES : not that easy to find in the right size, hard to handle, might break uopn rapid heating, wont conduct hreat out.

Epoxy :
ADVANTAGES : cheap, quite easy to handle, wont break or disintegrate upon reasonable heating.
DISADVANTGES : might take fire, wont conduct heat out

any other suggestions?

dann2 - 4-3-2008 at 14:45

Hello Hashashan,

Will the Ti mesh be any better than say (as you used) the Scotch cloth?
You will not be able to use the Ti as the current carrier to the anode when it goes into a (Per)Chlorate cell (as you said) as the Ti/LD interface will passivate no matter how thick the coating of LD is.

You are really back to the massive anode with cloth reinforcing, this time the cloth is Ti.

US Pat 850380
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

is somewhat similar. It uses a Ta substrate (its really a massive anode).

You could use the Ti mesh to carry current in the plating bath so long as you start with a near neutral Nitrate bath or start with a coating of Alpha from an alkali bath and then plate Beta. The 'substrate' (piece of plastic, glass or whatever) would simply be keeping the mesh straight.
If you used something that could be removed (wax?) you would end up with a novel, tubular anode (better than anything before, best ever, etc etc :D)
The 3mm is too small for this though.

Is it expensive?

Make sure it is actually Ti metal and not like this:
http://cgi.ebay.co.uk/WIRE-MESH-RIBBON-VERSATILE-ORIGINAL-TI...



Dann2

[Edited on 4-3-2008 by dann2]

hashashan - 4-3-2008 at 17:01

I don't want a massive anode, All I want is about 1mm coating and a hard substrate underneath(just mechanical strength)
the Current will be applied through a silver coating.

What is so good with PbO2 tube?

It costs about 7$ per meter.. not too expensive.
I don't know if it is pure Ti, that is what I have been told, it is anodized but still conducts current.
I will probably use glass as substrate, It can also be removed easily if necessary after the coating application.

dann2 - 5-3-2008 at 16:03

Hello,


About the tube shaped anode I was only joking that it was better than anything before etc etc (patent speek as it were), though a tube shaped anode if you manage to make one would be stronger and more robust (physically) than a flat anode of the same surface area. You would need to put a cathode inside if you intended to use the inside surface. That would take a bit of accurate positioning if the tube is only 3mm diameter.

You can find out if it is Ti by putting a small amount into a Chlorate cell as an anode. If the current flows for a few seconds and then fades away it is a valve metal. If the current keeps flowing then it is something else and will not be suitable. Do not use over 10 volts.

Cheers,
Dann2

hashashan - 5-3-2008 at 16:47

Dude I don't care if it is Ti as long as It will handle the first plating. ... well just see.
I found out how much a quartz tube of such diameter will cost .... god damn 90 euros per meter(I almost shit myself), I think Ill use glass and see what happens

dann2 - 23-3-2008 at 18:08

Hello,
The LD Anode is still going OK (one month). The current efficiency is very low. (20%)
I tried lowering current density. CE got worse.
Lowering temp. with CD kept at 250mA per square cm. CE went up to 26%.
I added 2 grams per liter Sodium Persulphate. The current efficience went up to 38%, but it came back down again when I added a mild steel cathode. I am not saying that the CE decreased because of the mild steel cathode addition, it looked more like the 'effect' of the Persulphate wore off the cell (if ya know what I mean, cos I am not too sure meself!!!). There was an absolutely horrible stink when I added the Na Persulphate to the cell. What was it doen anyone care to guess. Ozone? I don't think it was Chlorine.
I added a mild steel cathode (instead of the Ti cathodes that the cell was running with from the start), and the current efficiency came down to about 15%.
I am doing too much chopping and chaging. I take sample but don't have time to titrate for some days after.

It is slowly but surly going towards a Perchlorate cell. It contains 300g per liter Chlorate at this stage. (It started with 300g per liter Chloride when it was started).
I added 2g/l NaF at start BTW. Cell is 2.65L. Current is now 10 amps. V is about 4.8 volts.

Anode OK though which is good.
@Hashashan
You got approx. 50% CE but then again you had trouble getting rid of Chlorate when you went to destroy it. Perhaps you have much more Chlorate than you thing (less CE than you think?)
@Anyone else measure CE with LD anode here?

Cheers,

Dann2

[Edited on 24-3-2008 by dann2]

hashashan - 24-3-2008 at 13:43

dann' most probably you are right. Its just that i usually got a positive test with MB after twice the theoretical time.. the chlorate-> perchlorate was quite slow probably.

what is the CE of Pt anode?
and how do people get up to 80% with LD?

tentacles - 24-3-2008 at 14:32

Pt and LD can have similar (for our intents and purposes) efficiencies.. the problem is, to get high efficiency you need to control the cell pH carefully. Realistically, you'd need something like a pH controller and a small pump to dose the dilute HCl into the cell. Might not be terribly expensive - an aquarium/hydroponics pH controller runs about $150 I believe.

But then again, you'd need a pH probe that can survive in a chlorate/perchlorate cell long term! I don't know if any could do that, but there are probably ones that will.

[Edited on 24-3-2008 by tentacles]

dann2 - 24-3-2008 at 17:25

Hello,

@Hashashan
If you got Perchlorate forming in good amounts at twice the 'run time' then you did not get too bad of a Current Efficiency (CE), approx 50%. When you say 'twice the run time', do you mean the run time of (theoretically) converting all the Chloride to Chlorate or all the way to Perchlorate.

Perhaps Pt has better CE in a non pH controlled cell that LD. All articles that you read comparing/discussing Pt/LD will be in relation to pH controlled cells.
I always though that you got about 50% CE when pH was not controlled and way up at 80 to 95% CE when pH was controlled. Approx. 50% is what people get when using Graphite (no pH controll). Lots of people have done it, but not many have used LD down the years because they just did not have the stuff (failed anodes etc).

I am currently controlling the pH of my Magnetite anode cell. It seems to be quite easy to do. I guestimated that I would need 0.2ml 12% HCl per hour into the cell. Set up my syringe pump to put 0.2ml per hour into it and it is holding the pH steady at 6.8/6.9 (bang on target). I am checking the pH every half day or so using a pH meter calibrated with a buffer solution at pH 7. Will measure CE in a few days and see what is the story.

Will then pH controll my LD cell and see how it does regarding CE.

Syringe pumps can be had on ebay for about 100 bucks.
Dont see why a cheap intravanous drip (bag hanging up with a tube and dripper yoke) would not do the job. Perhaps the pH will have a tendency to self control. If you add a small amount of acid too much, you will loose more Cl and pH will tend to increase etc etc. Perhaps no need for a pH meter in cell all the time.
When using pH paper to measure pH it is difficult to get a reading as the paper gets bleached.
Can anyneo tell, if you boil a small quantity of the solution before measuring the pH to get rid of the bleaching effect (Hypochlorite???) will that effect the pH measurement?
Suppose I could do this and see!

Dann2

hashashan - 24-3-2008 at 17:43

I meant the theoretical time for the chloride to convert to chlorate.

tentacles - 24-3-2008 at 18:37

50% is not bad at all for an uncontrolled cell, with any kind of anode.

hashashan - 24-3-2008 at 18:49

50% is great. but the chlorate-> perchlorate stage is much slower for some reason.

dann2 - 24-3-2008 at 19:40

Hello,

Perhaps there is much more Chloride still not converted to Chlorate? and the anode is still busy converting this Chloride to the Chlorate (and forming small amounts of Perchlorate at the same time) just a guess really.
Did you try adding some NaF or a Persulphate?

I attached an article from Ullman (thanks to KMnO4, no I'm not talking about Purple Haze...). It is a good read on Chlorate/Perchlorate stuff.
@Xenoid. It contains diagram of KCl and KClO3 mutual solubility.

Anyone access to French Journals??
Bull. Soc. Chim. France
A. Nallet, R. A. Paris.
1956, 488 – 494.
http://www.ingentaconnect.com/content/els/00378968
Not available online:(

Dann2

Attachment: Chlorine Oxides and Chlorine Oxygen Acids.pdf (819kB)
This file has been downloaded 2796 times

dann2 - 3-4-2008 at 09:45

Hello,

The Cell running the LD anode has been now been declared an official Perchlorate cell. The Perchlorate in on the increase.
It is slow, hopeing that it's not the LD anode that is slow to convert the Chlorate to Perchlorate but rather that there is still quite alot of Chloride still being converted to Chlorate in the cell. I am taking samples every two days. The cell has a run time of 50 days (all Chloride to Chlorate) at 20% efficiency.

Attached is a file I came accross on DSA in Chlorate cells. It would appear that the optimum pH is somewhat lower that I had seen elsewhere. The seem to run their cell at not the optimum Chlorate formation pH but also to minimize Chlorine escaping from cells. (Environmental or Economics??)



Dann2

Attachment: urn_nbn_se_kth_diva-4681-2__fulltext.pdf (2MB)
This file has been downloaded 980 times

hashashan - 3-4-2008 at 16:39

Hi,
Im really sick of salts creeping up to the connections.
How do you guys install the anodes in your cell?
dann I didnt understand what is that liquid resin from your website.

Anyone has a good method for a connection?

dann2 - 4-4-2008 at 13:45

Hello,

For connection to Ti I just use a brass bolt through a hole. The bolt goes through a loop on the end of Copper wire.

The resin is polyester resin. It will be available in car accessory shops or garages. It is used to make Fiber glass reinforced plastic. (FiberGlass). Also used to make/repair fiberglass boats.
It's like epoxy resin. It is a liquid which sets rock hard in about 5 to 10 minutes (after hardner, Benzoly Peroxide has been mixed it).
'Wets' things well and seals well. I find with silicon sealer or hotmelt that the salts get around them.

http://www.halfords.com/webapp/wcs/stores/servlet/SearchCmd?...

Can you get roofing pitch. Black stuff for felt roofs. This would probably do the trick. I never used it. Definitely cheap. You local builders providers might give you a sample.





Dann2

[Edited on 4-4-2008 by dann2]

hashashan - 4-4-2008 at 16:18

I think that pitch might react with all the chlorine and stuff.
The hotmelt glue and epoxy reacts with it, and gets brittle and falls off with time

markgollum - 4-4-2008 at 21:51

I have a nice chlorate cell using a MMO anode and Ti cathode but in my design the electrodes are bolted (with brass bolts) to a copper rod that extends into the electrolyte. So far I have tried to cover the rod with two different types of epoxy both failures. The first was a special gray colored marine epoxy designed for permanent immersion in salt water. It turned white and began to come off as a soft white powder after only about 24 hours in a hot chlorate cell. Next I carefully sanded the white powder off until I got to the undamaged epoxy (the epoxy was about 4mm thick at the beginning) and put a coating of a different brand of epoxy on. This layer lasted about 36 hours but turned soft, yellow and could be peeled off the first layer.
My cell is now on hold until I can find a suitable replacement.
I was thinking about Devcon Titanium filled epoxy putty, or Devcon Alumina filled epoxy coating as their properties are outstanding. (max working temp about 177C as well as being resistant to solvents, acids, most bases, and salts.) The alumina filled putty is 90% alumina so it really has outstanding chemical resistance.
However, last time I checked they were about $130/lb on eBay and that was the smallest you could purchase.
Does someone know of a putty or claylike substance that would not require firing, adhere to metal/epoxy and solidify to a non-porous form that would not conduct any moisture/salts?
Or does fiberglass resin hold up semi-permanently in a hot chlorate cell environment?

I am aware that some websites (Dann2 I think) claim that MMO coatings should not be used above 40C but the literature I have read states that MMO anodes can have life times on the order of 7years, even in a hot cell. (I am saying this because I don’t want to have someone discuss temperature and MMO anodes in this lead dioxide thread).

dann2 - 6-4-2008 at 10:04

Hello,

My Chlorate cells have never been up at 70 or 80C for long periods of time. The resin works ok when temperature is lower for long periods of time. Never had it fail.

Car body filler (Made by Isopon may do too).

@Markgollom You are right about the temperature.

Dann2

dann2 - 12-4-2008 at 17:36

Hello,

Titrated my LD anode cell two days ago. 310 grams per liter Chlorate. This cell is sloooooooooowww.
I am beginning to wonder if the whole concept of Chloride to Perchlorate is a bit daft. If the cell is working at 20% CE (ie. my cell) for making Chlorate. When the cell starts to make Perchlorate there will be a bottle neck when it destroys all Chlorate present (converts it to Perk) and then sits around waiting for more Chlorate to form. The bottle neck will occur because it only takes 1/3 the amount of electrons to make a mole of Perchlorate from Chlorate when compared to making Chlorate from Chloride + the fact that the Perchlorate formation may operate at say 70%CE.

Anyhow, anode looks fine. There is Lead depositing on the (Ti) Cathodes, at least I think it is Lead. Will scrape off some and see if it will melt. It this anode fails by wearing out it will last for a year or so judging on the amount of deposit on Cathode. You would not know looking at the Anode that there was any wear at all.

Dann2

hashashan - 13-4-2008 at 02:25

Dann
did you try to check CE in cells with Graphite, or MnO2 anode?

dann2 - 13-4-2008 at 05:50

Hello Hashashan,

Never titrated with Graphite. Never used MnO2.
Will try soon.

Dann2

dann2 - 2-5-2008 at 15:17

Hello Folks,

My Ti substrate anode has been working now for 9 weeks in a cell going from Chloride to Perchlorate, approx. 2.250 liters.
It is ridiculously slow. Can now get yougart ppt when I add some KCl. The Chloride continues to fall as well as the Chlorate. Have not had time to titrate Chlorate lately. I check Chloride by taking a 0.5cc sample. Dilute with 30cc water. To this I add drops of known dilution Silver Nitrate solution untill I get no more ppt. This takes a few days as I must leave the cloudy solution to settle for 12 hours or so.
Some pics of anode below.
There is a large amount of Lead ppt on Cathodes. I scraped it off, dried and weighed. It was 6.7 grams.
I think I can smell Ozone coming from cell. The current has fallen by about 10% in the last 3 days.
<a href="http://s168.photobucket.com/albums/u200/anodes_2007/?action=view&current=top.jpg" target="_blank"><img src="http://i168.photobucket.com/albums/u200/anodes_2007/top.jpg" border="0" alt="Photobucket"></a>

<a href="http://s168.photobucket.com/albums/u200/anodes_2007/?action=view&current=lead_2.jpg" target="_blank"><img src="http://i168.photobucket.com/albums/u200/anodes_2007/lead_2.jpg" border="0" alt="Photobucket"></a>

<a href="http://s168.photobucket.com/albums/u200/anodes_2007/?action=view&current=lead.jpg" target="_blank"><img src="http://i168.photobucket.com/albums/u200/anodes_2007/lead.jpg" border="0" alt="Photobucket"></a>

<a href="http://s168.photobucket.com/albums/u200/anodes_2007/?action=view&current=cleaned.jpg" target="_blank"><img src="http://i168.photobucket.com/albums/u200/anodes_2007/cleaned.jpg" border="0" alt="cleaned"></a>

D2

dann2 - 15-5-2008 at 19:50

Hello,

I stopped the cell today. The end had arrived as I cannot detect any Chlorate using the titration method I am using from a cell sample size of 30ml (alot).

Checked Chloride level 5 May and it was at 6 grams per liter.
Chlorate level was at 108 grams per liter.

Today I could not detect any Chlorate.
When I attempted to check Chloride level (using known dilute solution of Ag Nitrate in a
measured and diluted cell sample as I did before) I got a light brown/fawn colour that is taking a very long time to settle. It would appear that Chloride levels have increased (if the brown ppt is Chloride).
Can anyone suggest what the light brown/fawn ppt is?

What is the actual colour of Silver Chloride anyways. When you are doing a Chloride test using Silver Nitrate the Siver Chloride appears as white clouds. When it settles to the bottom it looks black. What colour is the stuff if you purchase it (Silver Chloride) in a jar?

This cell has been running for approx. 10 weeks at 10 amps. Thats 16,800 amper hours.
With approx. 720 grams Na Chloride at the start, 12.3 moles, it will take 2640 amper hours to convert to Perk. at 100% CE.
I calculate this cell current efficiency at approx. 15.7% CE.
It is too slow, but gets there in the end. At least the Lead Dioxide is capable of taking the Chlorate to very low concentration.

The cell has been emitting Ozone for the past three weeks, at least that what I presume the smell is. There is only a small amount of Lead being deposited onto the Cathodes. It would appear that most of the Lead deposited onto the Cathodes approx. 3 weeks ago and has since slowed down. I cleaned the electrodes as shown in picture above.
There is a small amount of brown material at the bottom of the cell, perhaps one gram weight. The liquid is crystal clear. Cell is 2.25 liters BTW.
A drop of K Chloride solution causes an immedieate ppt of K Perk that sits on the surface of the solution.

Will extract Na Perchlorate.

Next up is a pure Perchlorate cell using pure Chlorate (containing approx. 2% Chloride).

Dann2

Anode update

dann2 - 15-6-2008 at 09:32

Hello,

The beginning of the end of the Ti substrate LD Anode is beginning (if ya know what I mean).

It had been running for a total of three months. Current efficiency in a Chlorate cell was poor.

When it was used in a pure Perchlorate cell is give low CE and was inclined to wear. The coating was already thin when it was placed into the Perchlorate cell.
The anode has been lying idle for some weeks now as I did not have time to post.

I don't have much data for same reason.
CE in Perchlorate cell was low but it did the job.
It still works OK. The voltage of the cell has increased a volt or so though.

Next anode will have a much much thicker coat of LD on it.

If I get time to titrate Perchlorate cell samples I will report here.

Dann2

anode.jpg - 71kB

hashashan - 15-6-2008 at 20:57

Dann are you using stirring?

dann2 - 16-6-2008 at 15:15

Hello Hashashan,

Did not use any stirring. The cell was shallow (the anode and cathodes went all the way to the bottom) so I presumed that the Cathode and Anode bubbles were sufficient to keep the cell stirred.
Perhaps stirring would have helped. Garage Chemist (in a Pt Anode cell) says stirring is essential.
Brown (LD) started to appear on the cell bottom from day one. Some Lead on Cathodes too.

The anode is still going to last quite a long time even though the Ti is exposed in places. The thichness of LD at the top of the anode is still quite thick. I (alas) don't have any Chlorate for to start up a new Perchlorate cell. I have gallons of Perchlorate contaminated Chlorate solution.
The final Chlorate concentration of the Perchlorate cell was 11 grams per liter. Cell volume was 0.88L. Current efficiency for the first day running was 47%. After 32 hours running a 'yougart precipitate' was obtained when KCl solution was added to a cell sample.

Will begin a pH controlled Chlorate cell with the (weary looking) anode.

Dann2

hashashan - 26-6-2008 at 00:15

Hi, got a question here.
anyone tried to electrolyze Barium chloride with PbO2 anodes straight to barium perchlorate?
I guess it will demand high current densities and the erosion rate might be too high.

12AX7 - 26-6-2008 at 00:33

I've tried electrolyzing with graphite to make chlorate, which worked fine. I don't see why perchlorate would be very different from electrolysis of the sodium salt.

Tim

hashashan - 26-6-2008 at 01:06

did you manage to separate the chlorate from the chloride?

12AX7 - 26-6-2008 at 02:30

Not yet. I have some isolated, but there is still plenty of chloride left to convert. I should run some more amps through that some day. Given the solubilities, barium is definitely a batch process, not like sodium chlorate.

Tim

hashashan - 26-6-2008 at 02:43

How are you plannning to separate the products?
both of them are highly soluble

hashashan - 26-6-2008 at 03:08

Sorry for about the double post
but I just got this crazy idea of making a composite anode that will be made from Carbon rods impregnated with PbO2 all the way through them.

How about soaking Carbon rods in Pb(NO3)2 solution (preferably under vaccum) and then oxidising them with bleach.
After that a short electrodeposition will ensure that all the PbO2 will be converted to the beta form. Also the electodeposited PbO2 will protect ehe Carbon at all times, even after heavy usage there will still just be loose Carbon particles in a single piece PbO2 anode, thus we will get a reliable strong PbO2 anode with an electrical connection.

12AX7 - 26-6-2008 at 08:16

I don't see that working, the graphite is already a more-or-less continuous matrix. You would get PbO2 particles in a graphite matrix. Extremely porous graphite (I'm thinking foam here) might have enough space that you could eventually be left with a PbO2 foam as the graphite erodes out.

Tim

hashashan - 26-6-2008 at 11:22

Ill try that
I dont think that the graphite will erode out.
I do believe that the PbO2 will coat it. And the more porous it is the better.

dann2 - 26-6-2008 at 15:09

Hello,

I cannot see the Graphite not eroding out. If it is chemical erosion only they you may be left with a LD 'sponge'.
Graphite erosion is both a chemical and physical process. The physical process (helped by sealing porous Graphite with Linseed oil etc) involves pieces of Graphite being removed not unlike the way water/ice weathers rocks. Graphite particles get heaved out. This will crack and destroy the LD IMHO.

Dann2

Picric-A - 18-8-2008 at 08:36

Just a quick question on using lead dioxide.
I now make my PbO2 by electrolosis of H2SO4 using Pb electrodes.
This deposits a black/brown ( i guess PbO2) layer on the cathode(i think... maybe anode)
will this layer be enough to use in a perchlorate cell? I have never made chlorates/perc's myself but this is something i would really like to learn how to do,
thanks,
Picric-A

12AX7 - 18-8-2008 at 08:48

Not likely, it's not adherent in my experience. Like, it's flaking off right?

Tim
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