Thoughts On Anodes

The guy was me

Dann2, thanks for that great idea, I still have plenty of that stubs from previous cells and this week I discovered a HUGE PILE of graphite pieces (probably sintered, some cm long, since it was on metalurgical engineering park on university ) ; collected some hundred grams (several pieces) to future testing, probably worth eforth using in that scheme, although they are somewhat irregular pieces.

Only hope the electrical resistance to drop reasonably well with this bipolar scheme to give good currents (+5V PC PSU).

[Edited on 19-3-2009 by Aqua_Fortis_100%]

My ph control setting is now working

I start from the idea of Dann2 to make it but i change some stuff cause it has a problem in his setting. The first idea was to put a bottle link with a tube to a small tip. But the problem of this setting was that when the level of water go down, the droping rate was going down too... So to get a constant droping rate, the level of water need to always be the same. To more easily understand the setting, i post some pic-->.

With some calculation, i find that i need 1 drop every 12 sec to get 13,4 ml per hour, wicth is what i need for my 100Amp chlorate cell.

I will try this ph control systheme when my cell were be finish, so it is maybe be ready in one or two month...

The last thing, swede, i search for the kind of clip to put at the end of the wire to plug to the anode and the cathode, but i the biggest size that i find was for 12 gauge wire... So i made from copper tubing, will it be ok? Also, thank for helping me for the PID controller setting.












[Edite le 21-3-2009 par Bikemaster]

@Bikemaster - all looks good! Very clever arrangement! Just realize that the portion of the HCl rig open to the atmosphere will vent a bit of HCl fumes. If there is any ferrous metal in the vicinity, it will soon corrode. But nicely executed using components that are essentially free. The copper looks fine, too. There are a hundred ways to attach heavy cabling to electrodes, all of which will work, and I'm sure yours will too. When it's running, check for heat. Most of the heat generated in a high-amperage setup comes from the titanium straps' resistance, and the connector both helps the current along, AND acts as a heat sink. Cu conducts heat nicely, and the cables themselves will help carry the heat away.

It looks like the bug has bit yet another poor (per)chlorate victim!

To all interested: The LD anode(s) that I plated in January are still untested, but I have finalized my LD paper, "Lead Dioxide for Dummies." It includes both the research and the experimental portions of this whole thing, although no real conclusions - yet. I will add those when I test the anodes.

The download is 1.1 megabytes due to pics. Guaranteed virus-free, hot off the press.

http://www.5bears.com/ld/ldfd01.doc

Even if this particular method does not work, I think guys may find the information helpful. Good luck to all!

[Edited on 21-3-2009 by Swede]

I have been following this thread for a while now, and I think it's time to enter in.

I was visiting a local producer of MMO-electrodes today. It was interesting to see the process a little closer. Ofcourse I asked to buy some MMo-sheets (that was really my main reason for the visit). He told me that I couldn't as it would be much to expensive, he had to put up an order and all that. The only possible way to go was giving me some spillover. I left with 3.5 kg of Ti gr1 and MMO-sheet metal
I suppose sheet is better then mesh, right?

Now it's time to start working on the first test cell. I will make it simple, maybe with some form of ph control, current limiting and a PC power supply. Some kind of glass jar (just have to eat the jam first) will do as a container.

I post my successes (or whatever) when I get something setup.

Maybe the temperature will change for differente substrack... i read more on GSLD, so for plating graphite the temperature need to be under 55 C. but for MMO it seem to be more.
For the solution size, the only reason that i want to make smaller size, is for the price. but can we re use the solution for more that one plating??? It will be a good way to save chemical and money.

Did you really get 3.5 kg of titanium and MMO. WoW!
If it is possible, can i buy some??? like a small sheet of 2x6 of mmo and a 6x8 sheet of titanum
good luck for your futur cell

I have 3 of the ebay <cheap> mmo anode. Personaly i am not thinking that is really cheap because i think that we pay a lot cause the anode is ready to be use. (handle, perfectly coated and because it is the only seller on ebay). For those anode (2x6), i pay 80$ each and if i want to buy some today it will cost me 100$ because of the canadian money rate...
I don't know how much you pay your mmo and titanium plate but i am pready sure that it is less that 100$can for each (2x6).
For the shipping price, i go on (Royal mail Airmail) and the shipping price don'tseem to be a lot
If you want to keep your titanium and your mmo, it is perfectly your choice but i just thinking of this because if you give me the adress of the seller i can not buy 3,5 kg too and the price of the titanium and the mmo will be bigger... but if the price of these stuff seem to be good, send me the adress and i will try to order some stuff.

thx

For LD plating, I have no idea how the eBay material will work. The anodes I plated in January were a different brand, and cut from a full sheet I purchased. MMO formulations are application-specific. Pool chlorinators, chlorine generators, chlorates, and general chlor-alkali processes, all seem to have different formulations, most of them a trade secret.

We know the eBay MMO makes chlorate, but beyond that, I have no idea. It seems to be good, sturdy stuff, and may plate nicely, but I need to set my rig up again, which I was planning on doing anyhow very soon. I will try a small piece of the eBay MMO.

My new goal is a more modest coating of LD rather than the mass that plated on my Anode #2. Before I do that, I need to check the bath for Pb++ concentration and a few other things.

Overall, though, it seems that MMO is becoming more and more available... sorry dann2, the days of graphite as the primary tool for home chlorate production appear numbered!

Gamal, nice score. There is NO substitute for contacts in the industry, legwork, or both.

[Edited on 24-3-2009 by Swede]

Quote: Originally posted by Gamal

I left with 3.5 kg of Ti gr1 and MMO-sheet metal

That was a delicious piece of spillover! I reckon that you shook your fist at him!!
What do they normally do with their spillover (scrap pieces?). If you can get your hands on the stuff for a good price every month or so, you could have a great ebay thing going on selling MMO sheet. (and doing the poor beleaguered Chlorate making community a great service too).

@Swede
I weighed a gouging rod today. 90 grams, it's 13mm diameter. If you take 15% off this for connections and the fact that the last small slivers will fall down to the cell bottom and not be available for making Chlorate you are left with 76.5 grams. At 10 grams wear per Kg Chlorate (you can get 6 grams wear with EDM Graphite) that equates to 7.5 Kilo of Chlorate per Gouging rod!!!!!!!!!!!!!!!! Yeeeeeeeeeeee Haaaaaaaaaaaaaa

BLESSED BE THE GOUGING ROD AND ALL IT'S WORKS
LONG LIVE THE POOR MAN'S MMO

Moving on to less serious things I plugged a 'killawatt' meter between the mains supply and my setup. Cell runs at 7 amps and it's a computer supply. It it burning up 62 watts. Thats one unit every 16.1 hours = 1.5 units per day = 24 cents per day = 720 cents per month. I was surprised how much it actually is. Most of the power is going on the supply. The cell is only burning up approx. 27 watts.
EDIT: Forgot to mention that I have a piece of hot Nicrome wire between cell and supply.

If you are searching for Titanium in Europe try the German ebay at:
http://www.ebay.de/
Search for Titan blech (titanium sheet)
Search for Titan stab (titanium rod)

Anyone know the German for Titanium mesh?
I have no German. Use the Alta Vista translaters if you have to read the descriptions though they are usually self explanatory. Make sure the seller does PayPal. Bank transfers are a pain.

Still running my cell with the Poor Man's Platinum (Lead Dioxide). There is little or no erosion on the LD. Guess it is due to the pH controll though it is early days for the cell yet. It has not reached the 'difficult' zone yet (low Chloride concentration).

I wonder since there has been a terrible failure rate on Graphite Substrate LD Anodes would it have been the fact that they were always being used in a non pH controlled cell. If pH was controlled they would probably have faired better.

Dann2

[Edited on 24-3-2009 by dann2]

Haha, dann2, you are a dogged advocate of graphite! While you are decanting and getting ready for a decomp to potassium, I am washing masses of snow-white potassium chlorate crystals. MMO is the King of Chlorate!

Gamal, last fall I attempted an elaborate 2-cell pumped system, which I called the "T-Cell". The system used a hot "Electrode Cell" (EC) and a cool "Collection Chamber", the CC. I used Potassium salts.

If you're interested, I blogged the whole experience; I don't know if you've seen it or not: Starting about here....

http://www.apcforum.net/forums/blog/swede/index.php?view=sho...

In summary, it was a disaster with potassium once the crystals began to form. Prior to crystal formation, it was working spectacularly. By varying the pump rate, I could create a dT between the two cells of 20 to 40 degrees C. But once the system was saturated with chlorate, as the liquor traveled through the tubes, it cooled almost instantly, and the tubes jammed hopelessly with crystals.

It was a huge effort that I am not ready to repeat at this time, mainly because a single, large cell works so well... I couldn't see the benefit of circulation. But that doesn't mean it doesn't work. Commercial plants circulate (with sodium salts) or have a linear process, with multiple chambers, and a saturated chlorate solution coming out the end of the line.

There are few plastics that would have a long life in a chlorate system. The big four that I am aware of, and that I know work:

(C)PVC
PVDF
PTFE
PET

For tubing, there are Tygon formulations that do work, but a better option is a wide-bore CPVC pipe system vs. flexible tubing.

Hello,

I may have posted this monstrosity here before but it is (IMHO) the 'de Nora' of all Chlorate cell designs!

If you are going for a crystallizer/collector you really need a miniumum of two large chambers or better to have three chambers if you are going for pH controll.
The crystalization chamber needs to be cool.
The chemical Chlorate chamber (assuming pH control) is best hot, both for the small increase in efficiency and to stop the formed Chlorate coming out of solution.
The actual chamber with the electrodes can be quite small in relation to the size of the Chemical Chlorate formation chamber. If not using pH controll then two large chambers will be OK. One is the Chlorate cell, the other the crystallizer.
The problem point is Point A, as discovered by Swede.
A filter bag may be a great help if using the QUEEN[/COLOR] (did ya ever play Chess) of Chlorate Anodes. (pH controll definitely recommended).
Point A will be a problem with either Na or K as you are going to be dealing with saturated solutions for both. It will just take longer for the Na system to reach saturation.

Dann2

I like it. Sodium would absolutely be the way to go. If one has the ability to create such a beast, then one also has the knowledge of how to process the goodies!

But dann2, you do realize the cost of such a system would far outweigh the cost of acquiring a proper anode for it!

Graphite in that system would be like using spray paint to touch up a Mercedes!

Bismuth source

Hmmm...about a year ago I posted this about a complexing of bismuth as a strategy for producing bismuth in soluble form in a less acidic medium, and there were several other strategies which have been described also.
http://www.sciencemadness.org/talk/viewthread.php?tid=9783&a...

I have a bit more on this, possibly from an ancient reference Take unto thee of bismuth nitrate two loth and of mannite five, and triturate together well in an agate mortar whilst murmuring the appropriate incantations prior
to dilution with a hundred loth of twice blessed rainwater,
and if not mannite then sorbitol or glycerol shall suffice but
the loth equivalency / conversion function key on my scientific calculator is worn out, so more now I cannot tell

One part bismuth nitrate plus three parts glycerin reportedly forms a water soluble compound also.

Soluble complexes have also been mentioned, glycine, EDTA,
and nitrilotriacetic acid are operable.




http://sciencemadness.org/scipics/Bismuth%20nitrate%20compou... direct view link for pdf , download save link below

Attachment: Bismuth nitrate compound with Mannitol.pdf (102kB)
This file has been downloaded 836 times

[Edited on 27-3-2009 by Rosco Bodine]

Hello,

@ Tentacles
I think you should refer to the device as the PMSW*
Looks good. I must put one together myself. I have a large AC welder and it would be fairly easy to make up electrodes and a clamp.
One thing about Microwave transformers (AFAIK) it that they will pull a very high current from the supply when there is no load on the secondary winding. The reason for this is that the microwave transformer is designed as skimpy as possible and the designer knew that there would ALWAYS be a load connected to the output winding (the Magnetron). This allows them to only put about half the more usual amount of windings on the primary and get away with it. When you go to use the transformer (either with a new output winding or even the transformer as it came out of the oven for some High Voltage application) and you do not put a load on the output (when you are not actually welding in your case) you will get a very high current going into the primary, much higher than a 'properly' designed transformer.
A good way to counteract this is to use two transformers with the primarys in series and you can put whatever you wish on the (in your case rewound) secondaries.
This heavy current may not be helping the fuze. Can you measure the input current when you are not welding with perhaps a clamp meter?
Hope I am right on the above.

Cheers,
Dann2

*Poor Mans Spot Welder

Quote: Originally posted by tentacles

[I] need a SSR to switch the transformer. I blew the crap out of the 15A fuse in the background of the picture. [...] The windings only got a little warm after welding all those anodes - about 28 welds. The bus bar and electrodes got quite warm.

Quote: Originally posted by dann2

I must put one together myself. I have a large AC welder and it would be fairly easy to make up electrodes and a clamp. [...] One thing about Microwave transformers (AFAIK) it that they will pull a very high current from the supply when there is no load on the secondary winding.[...] This heavy current may not be helping the fuze. Can you measure the input current when you are not welding with perhaps a clamp meter?

We had discussed pH control in some detail in this thread, and I am convinced that it can be done very well, if your cell has sufficient volume (4L or better) using TIMED dosages of HCl. I found that 1 minute ON, 59 minutes OFF, of a Hanna dosage pump, was perfect.

The trick isn't the dosing pump, which can be expensive; the trick is in the timer. Every timer I found locally and OTC had major drawbacks, such as coarse controls and a tricky interface. Industrial timers and controls are expensive. Then I found this one, a real steal at $32.




http://auberins.com/index.php?main_page=product_info&cPa...

I received it today, ran a few tests, and found it to be perfect, giving me control to the minute or less. This means I can set my dosing pump on a schedule that will make the system more stable. It has an internal relay that can drive the dosing pump, but I am going to use the mechanical relay to power a SSR instead, to prolong the life of the mechanical relay contacts, which does not look serviceable.

Hope this helps someone. The same relay can control a solenoid valve or just about any device imagineable to administer HCl to a cell.

[Edited on 31-3-2009 by Swede]

Quote: Originally posted by Swede

If you can find a foot switch that can handle the primary current, that would perhaps be an easy way to control it a bit, although the inductive kick-back, I'm not sure where that energy would go! [...] It's odd, I never really thought about the inductive thing when the primary is turned off, and given that, would have expected a short life for the SSR, but it's soldiered on for years now.

Homemade dosage pump

I've been thinking about an easy way of building my own dosage pump. The ground idea is shown in the pic below.
It's a center wheel with three or four smaller wheels, maybee spring loaded, pushing a hose against an outer rail. When the center wheel turns the liquid in the hose is squeezed thru the hose in the rotation direction.
The weel could be turned by a low gered electric motor like a servo. The motor can be controlled by a timer like Swede's.
If you know the inner area of the hose and the turning speed of the motor, it's easy to calculate the time and interval for a specific amount of liquid to be trasported.

The construction should be quite simple. My biggest problem is to get a well working hose. It has to be very flexible and withstand HCl. I think silicone should work, but I haven't been able to test it. Does anyone have a suggestion.





[Edited on 1-4-2009 by Gamal]

Thank's dann2! It's allways nice to know what you are trying to build

I like the peristaltic type (allmost invented it ). It looks like they use teflon or silikone hoses most.
I'm sure I'll use it with uther chemicals, so I think teflon is the best choise then.

What do you think about using a needle bearing with some of the needles removed and some type of clamp over it. It would make a very simple construction I think.

Gamal, I don't want to discourage ANY DIY project, but be aware that you can pick up used peristaltic pumps for next to nothing off eBay. The work involved in making one from scratch would not be trivial!

If you want to see what's out there, search for peristaltic pumps or "Masterflex" which is a series of pumps and heads offered by Cole-Palmer. As for tubing, there are dozens of formulations and sizes, many of which will do HCl with ease, but PTFE is a different beast. Besides being expensive, PTFE tubing has little elasticity and has a limited lifetime and efficiency in a peristaltic head.

Here is a page with technical resources, including tubing compatibility:
http://www.grayledge.com/MasterflexBarnantIPPumps.html

Another plastics vs. chemical compatibility guide:
http://www.innocalsolutions.com/TechInfo/ChemComp.asp

Tygon is a good choice. Yet another tubing URL:
http://uscorp.thomasnet.com/category/tubing-hose-saint-gobai...

We also tend to forget about good old gravity as a means to deliver. Given some head pressure from a vessel higher up, all you need to do is turn a suitable solenoid valve on and off.



[Edited on 2-4-2009 by Swede]

@dann2 - very good point on the LD info. I need to do more research on the evolution of nitric as a function of coulombs, and also the mass of LD with the same parameter in mind. I also need to attempt to portray some of the chemistry as a balanced equation.

The deluxe timer is finished. Remember, this unit is designed to control HCl addition via a dosing pump, down to the second.

I found the ideal box for this sort of project - rather than use electronics enclusures, I simply used an outdoor PVC junction box from a hardware store.

The lid of the box was slotted, cut, and drilled for the essentials - an outlet, switch, 115VAC neon light, and ov course the timer itself:



Then, I populated the lid and began to wire it appropriately, using mostly crimp terminals.



The finished project - It came out nice, and should satisfy any lab needs for a precision timer.



In use, the switch powers on the timer, and enables the system. When the timer activates the SSR, the neon light illuminates, and of course power is delivered to the outlets.

One oddity that I overlooked... an SSR has a minute leakage across the output terminals, and having nowhere to go, the hot receptacle gets charged to 120VAC. I remembered this in the initial tests, when I put a DVM across the outlet with the power off, and to my dismay, found 120V there. But if you plug something in, it does not work. Only when the SSR is properly switched ON via the timer does the attached appliance (in the test, a portable radio) turn on.

It probably doesn't hurt anything, but it bugs me. Perhaps a resistance to pull the leakage to ground would eliminate it. I'd guess the current would be microamps. Any thoughts?



[Edited on 2-4-2009 by Swede]

Dann2
I'm sorry, I'm swedish. It was a direct translation. At least you had some fun
It's like a ball bearing but with small rolls instead of balls.
If I can pick some of them out and clamp the hose between it and a rail of some type, I only have to turn the bearing to pump the fluid.

Thanks Swede for the links! I think I'll try PVC at first. However I have a feeling it will harden after some use.

Dann2
I've found the word for my "needle bearings". It's linear bearings

Neutralizing with liquid from neutral tank

Hello,

@Swede
Your calculation is slightly out but not a big deal. You stated .672 moles LD instead of 0.627 (64 grams Nitric acid as opposed to 84 grams).

I have a question you's can think about. If you go to use a two tank system with a pump in between. One tank is plating (and will hopefully have between 6 and 10 grams Nitric acid per liter from the pumping effort), and the other tank is neutral (an excess of neutralizing Lead compound in it but not acutally suspended in the liquid as we want liquid only going into plating tank(use a filter or something)).
I calculate that at 100% plating CE you will get 2.35 grams Nitric acid forming per amp per hour.
How much of the neutral fluid do we need to pump so that the plating tank stays in the 6 to 10 grams per liter Nitric acid region.
It is easy enough to figure out how much solid compound to add to a plating tank. It's just a matter of keeping the moles happy but the liquid addition stuff has me stumped (it may be the late night, the absolute Alcohol and pills etc )

See cut and paste below for some of my reasoning (rambllings). Your welcome to check my figures!
_____________________________________________
<b><i><u>The tank should have a reasonable
volume in relation to the amount of Lead Dioxide that you are going to plate in one sitting.</i></u> </b><br>
Nitric acid is formed as plating progresses. To stop the concentration of Nitric acid from becoming too high you must have a suitible large tank (if using a one

tsnk system) or if using two tanks with a pump then the total plating solution volume need not be so large. You must add neutral solution to the plating tank at

the appropriate rate.
<br><p>
It would appear from patents etc, that the best concentratioin of Nitric acid to have in your plating bath is in the region of 6 to 10 grams Nitric Acid per liter. The

Nitric acid concentration will increase once you start to plate. You will get two moles of Nitric acid forming for every mole of Lead Dioxide that you plate, (126

Grams acid for every 239.2 Grams Lead Dioxide, = 0.527 grams acid per gram Lead Dioxide deposited). Most amateur Anodes end up getting formed from

baths with much more that the ideal concentration of Nitric acid. If using a one tank system a large tank is necessary. If you start your plating operation off with 6

grams per liter Nitric acid and you want to avoid the acid concentration going above 12 grams per liter Nitric acid you will need a tank size of 87.8ml per gram

Lead Dioxide that you want to deposit. <br>
Figure out how many grams of Lead Dioxide you need to deposit to form your Anode from the projected Anode dimensions minus the substrate volume

multiplied by the density of Lead Dioxide (9.37 grams per cc). <BR>
For example if you want to deposit 100 grams Lead Dioxide (not a large Anode) and you decide to start off your plating solution at 6 grams per liter Nitric acid

and you do not wish for the acid concentration to go above 12 grams per liter, then you need a minimum (one tank system with no adding in of Lead

Compounds during plating) of 100 multiplied by 87.8 = 8.8 liters. That's a big tank!! It would appear that adding Lead Compound (with or without a second tank)

is the sensible way to go if the acid concentration is to be kept in the most desirable range.<P>



The amount of Lead ion per gram of PbO<small>2</small> is 0.839 grams. The amount of Lead ion per gram of Lead Nitrate (Pb(NO<SMALL>3</SMALL>

<SMALL>2</SMALL> is 0.6256 grams. Therefor each gram of
deposited Lead Dioxide will use up 1.341 grams Lead Nitrate. The concentration of Lead Nitrate should not be let fall below 200g/liter. If the tank size is large

enough to keep the Nitric acid concentration at resonable levels then Lead Ion depletion of the plating solution will not be a problem. It is advantageous to

have the Lead ion and Nitric acid concentration as constant as possible during plating.

When going for a one or two tank system and adding Lead Compound the total plating solution volume need not be as large as when using a one tank

system with no addition of Lead Compound. If using a two tank system the neutral tank will have an excess of neutralizing Lead Compound in it. The pump will

slowly pump this neutral plating liquid into the plating tank at a rate that will keep the Nitric Acid concentration at approx 6 to 10 grams per liter in the plating

tank. <BR> If using a one tank system and adding Lead compound you will need to add the amounts in the table below<p>
Each mole of Electrons (26.8 amper hours) that flows will produce one mole Nitric acid (63 grams), assuming 100% current efficiency, which is equal to 2.35

grams Nitric acid forming per hour per amp.<br>
Another way to look at this is to say that a half mole of Lead Dioxide is plated onto the Anode per 26.8 amper hours, (119.6 grams Lead Dioxide per 26.8

amper hours) which is equal to 4.463 grams Lead Dioxide per amp per hour. You need to add Lead Compound to replenish the transfered Lead Ions and

depending on the Lead Compound you are using the weight added will need to equal the molar amounts of Lead Ion being transfered. The table below gives

the relevent molecular weights of the Lead compounds that are used and thus the amounts to add to the tank per amp per hour.<p>
<TABLE border=2>
<TBODY>
<TR>
<TD>Compound</TD>
<TD>Grams of compound to add to tank<BR>per amp per hour @100% CE</TD>
<TR>
<TR>
<TD>Litharge (molecular weight = 223)</TD>
<TD> 4.16</TD></TR>
<TR>
<TD>Lead Carbonate (molecular weight = 267) </TD>
<TD>4.985</TD></TR>
<TR>
<TD>Basic Lead Carbonate (molecular weight = 775)</TD>
<TD>4.824</TD></TR>
<TR>
<TD>Lead Hydroxide (molecular weight = 241)</TD>
<TD>4.508</TD></TR></TBODY></TABLE><p>
Since CE will be less than 100% you will need to add less that the table above states.
<p><br>
When using a two tank system with Lead Dioxide deposition being performed in one tank and an excess of neutralizing Lead Compound in the other tank

(neutral plating solution), then you must pump neutral liquid into the plating tank at the appropriate rate. Since the Nitric acid concentration in the neutral tank is

zero you need to pump this neutral solution at a rate of XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXx<p><br>

It may be possible to have an excess of Litharge at the bottom of a one tank system (if stirring is not used or perhaps intermittent stirring) which will react fairly

slowly with the Nitric as it is produced and help keep the Lead ion concentration constant and the Nitric acid concentration in the wanted range. If the Litharge

is too finely divided (small particle size) it may react too easily with the Nitric acid and be inclined to keep the pH of the bath too high (concentration of the Nitric

acid will be too low). You cannot use Lead Carbonate or Hydroxide or Basic Lead Carbonate in excess in the one tank system as they will keep the pH too

high (they react too readily with the Nitric acid formed) and the Carbonate will also cause bubbles/foaming as it reacts with the Nitric acid. You would need

some way to add (by hand even) the compound into the tank as plating progresses. A slurry could also be pumped perhaps.<br><p>

____________________________________________

Regarding Perchlorate making with LD, a higher current density on an LD Anode actually increases CE in the Perchlorate cell. I am not too sure what is the optimum CE. The cell is still needing acid to keep it at around pH of 7 which is different that the Graphite Anode cells. I don't know what the Chloride conc. is, but there is lots of Perchlorate at this stage. Some Lead appearing on Cathodes. Taking samples etc. Will report.

Dann2

That crock pot teeter totter arrangement is sounding better by the minute, huh? It's the whole tidal motion thing I tell you ....kind of like a respiration induced by
an iron lung, or gill ....in with the lower pH and out with the higher pH .....man it's like the scales of pH justice

And for so long folks have been told to get the lead out,
....hold the phone...here's to seeing how you put the lead back in

Guys, I am having difficulty in determining the mechanism whereby potassium metabusulfite (K2S2O5) is used to clean up traces of chlorate from a perchlorate batch. This is a partial repost of something I put on the APC web site:

APC Posting:

The metabisulphite creates,in an acid environment, SO2 gas, which is the reducing agent:

K2S2O5 + 2 H+ --> 2 K+ + H2O + 2 SO2

As for the actual reduction, this unbalanced equation is my best guess:

2K+ + 2SO2 + KClO3- --> K2SO4 + KCl

Does anyone know what byproducts are left behind from this reduction? The byproducts determine the next step in the purification process.

Finally, an interesting picture of the series of tests I ran to determine the point at which the perchlorate was "clean."



Comments, tips are appreciated. This (the cleanup of perc) is an important part of the overall proccess. The use of an SO2 generator, bubbled through the liquor, would introduce less contaminants, and make post-processing easier.



[Edited on 17-4-2009 by Swede]

Success in cleaning up perchlorate and purifying it with metabisulfite. As a continuation of my post above, I recrystallized the cleaned perc and harvested at maybe 5 degrees C. Yield from the original 20g was 17.62 grams of potassium perchlorate.

The tests for chloride consisted of

1) A Hach chloride titration strip - zero.

2) Several drops of strong silver nitrate. The sample remained clear. The silver nitrate test is sensitive, and yielded a nearly opaque white from tap water. The two are shown side by side, perchlorate on the left, tap water on the right, with added silver nitrate. The white coloration in the left test tube is reflection from the right test tube on a black background. The solution is quite clear.



Conclusion: negligible chloride.

Next, sulfate. Saturated lead nitrate was added to another sample. Insoluble lead sulphate should form if there was significant potassium sulfate in the perchlorate. Again, I noticed zero precipitation; the solution remained clear and bright.

If there is any sulfate in there, it is low enough to ignore.

Here is the cleanup procedure for POTASSIUM perchlorate that I think will work to reduce residual chlorate, and eliminate and reduction byproducts...

1) Calculate the amount of water needed to dissolve the perchlorate at 100 degrees; use 50% more water. 200 grams of potassium perchlorate would require 1.5 liters. Heat, but do not quite boil, the potassium perchlorate solution until all of the perc has dissolved.

2) Prepare a solution that contains 10% by weight potassium metabisulfite, relative to the amount of perchlorate you wish to clean. In other words, if you have 500 grams of perchlorate, start with 50 grams of potassium metabisulfite. This is cheaply obtained from home brew shops, and similar.

3) Add enough HCl to gently acidify the perchlorate solution, perhaps 15 drops per liter. Using a pipette, and with stirring, gradually add 1/2 of the potassium metabisulfite solution to the perchlorate. Allow it to stand for several minutes with continued stirring. Test the solution for chlorate. If still dirty, add additional metabisulfite.

4) Once clean, the solution needs to be neutralized, or made very slightly basic. The caustic of choice is KOH. Since the reduction byproducts are acidic, it requires more base on a Normal basis than the initial added HCl would indicate. Slowly add saturated KOH, dropwise, to the solution, and test with pH paper or a probe. When nearing neutral, it doesn't take much additional base to overshoot, so use caution. If you make it too basic, add a drop or two of HCl to bring it back to neutral.

5) Boil the solution down until the quantity of water is equivalent to the necessary mass of water for the amount of perchlorate used. Potassium Perchlorate dissolves at a rate of 200 to 220 grams per liter at 100 degrees C. An easy way to do this is to boil down until the very first crystals appear, and from there, allow it to first slowly cool to room temp, then refrigerate. Harvest the perchlorate by the usual means (decant + filtration) when the solution is at approximately 5 degrees C. Remaining potassium chloride and potassium sulfate remain dissolved, and are discarded. Wash the perchlorate with ice water and then cold ethanol. Spread the perchlorate out to dry, then ball mill to the desired consistency.

Hello,
This is a (very poor) photo of the eroded Anode. The picture shows both sides of the Anode. A fairly large area of Alpha Lead Dioxide is visible on one side of the Anode and seems to be holding up quite well. It is fractions of a mm thick. The Beta thats left can be seen on both sides at the top of the Anode. There are lots of cracks in it. The erosion of the Ti is showing up as two streaks on one side of the Anode mostly. The streaks are quite deep. There is erosion of Ti at the very top of the Anode too above the Lead Dioxide just below the lid.
There is also a picture of the Anode when it was approx. half way through the run.

Dann2


[Edited on 27-4-2009 by dann2]

Hello,

Actually I had posted your original quick and easy CE calculations at the bottom of a run time page and added two more. There are now five in total. I find myself always using them.
Process Formula for CE in %

Na Chloride to Chlorate 151.08 * Weight/Ah
Na Chlorate to Perchlorate 43.78 * Weight/Ah
K Chloride to Chlorate 131.22 * Weight/Ah
K Chlorate to Perchlorate 38.69 * Weight/Ah
Na Chloride to Perchlorate 175.10 * Weight/Ah

The cell above was run all the way from Sodium Chloride (300 grams per liter) to Sodium Perchlorate without stopping. I intended the cell to be 'green' but I (a mistake really) added NaF approx. one third way into the actual Perchlorate stage. This process (Chloride to Perk)was not done much in industry and IMO it was only done way back when power was cheap as new hydrodams were being put up in the Nevada area. This may not be correct. They uses NaF or Persulphate and Anodes were PbO2 on Graphite. I think F is out when using Ti substrate Anode of any sort let they be MMO or whatever in long term productin.
According to US Patent 7,250,144 (July 2007) F damages Chlorate Anodes. Since this is a modern patent the Anode are MMO. Perhaps it's just the coating or perhaps the substrate gets damaged or both.


Link to scientific study where they got 55-62% CE.
http://www.geocities.com/lllwolly/further/jes1976.html
The 42.6% CE (Chloride to Perk) that I got is not 100 miles from what it is sensible to expect.
NaF seems to make a big difference to CE according to the attached picture.
Persulphate is as good and better I have read somewhere else...........

The Chloride titration I am using is here:
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

The Grade of Ti I am using is Grade one. No Alloying elements, pure Ti.

The Anode was a first for me for PbO2 on Ti and is, at the end of the day, only an experimental Anode to see how the Ti + Tin Oxide + PbO2 system manufactured in a low grade, garage plating set up would perform. It had a very thin coating at the bottom (0.95mm think) + ceramic particles, which I had in the plating bath for to keep bubbles swept off the forming Anode, were imbedded in the coating and (IMO) did not help matters as far as erosion is concerned. (Repeating myself here).
I think an Anode with a proper thickness of coating and perhaps better control of the acid produced when coating will be a long term winner.
There is an article here that condemns thin LD Anodes for Perk production from Chlorate. They are massive Anodes though, grown on Ta wire. They claim the thin one's erode and the thick Anodes do not erode, sounds strange.
http://www.geocities.com/lllwolly/further/jesmar58/jesmar58....


Dann2



[Edited on 28-4-2009 by dann2]

Thanks for your feedback on KCl and solubility.

I include the following solubility data on KCl and NaCl (from Wikipedia):

Formula 0°C 10°C 20°C 30°C 40°C 60°C 80°C 90° 100°C
KCl 28 31.2 34.2 37.2 40.1 45.8 51.3 53.9 56.3
NaCl 35.7 35.8 35.9 36.1 36.4 37.1 38 38.5 39.2

At room temperature the solubility is quite close, but not at high temp. If I make a solution of 60 g 50/50 KCl/NaCl mix in boiling water, shouldn't the solution consist of mostly KCl then, at that temp? Then I can just decant it off.

I've been looking for water softeners, using KCl, but it's hard to find by a Google search. I'm also living in a town with very pure water, so I don't think I'll find it at any shop here.

The main agriculture store, here in Sweden, have replaced there "Kalisalt K 50" with something else they call Kalisalt. I actually bought 25 Kg of it, without reading on the bag first. It had only 3 % Cl in it. I got my money back as it was clear that it wasn't K 50.

Maybe I have to go to the Yellow Pages and look for farmers and start calling around to get fertiliser-grade KCl

Sorry for the mess of that table. I couldn't get the columns lined up. Is there any way of using formatted text?

Gamal

[Edited on 1-5-2009 by Gamal]

[Edited on 1-5-2009 by Gamal]

A true “gel” silica gel binder for graphite (or PbO2?) electrodes.

Quote: Originally posted by Swede

I know word documents aren't a popular download. Maybe this will be easier. I hope it works. It seems to, on my computer.

Hello Swede,

I measured the densities using two hydrometers.
One went from 1.000 to 1.2000. The next one went from 1.200 to 1.300 (g/cc).
The scales I used for the water and Lead Nitrate weigh to one tenth of a gram.

I like the idea of some Lead Nitrate plating bath standards. They would be a useful tool.

I think pH probes do not like heavy metal salts
I have seen a table of pH probes where 'OK/not OK' for heavy metal salts was a columb in it. Can't find it at this moment in time though. If you are buying a probe perhaps you need to consider this.

At this link
http://www.coleparmer.com/techinfo/techinfo.asp?htmlfile=Sel...
it says:
Silver/Silver Chloride (Ag/AgCl) vs Calomel (Hg/Hg2Cl2)
Ag/AgCl is the most common internal element, suitable for almost all applications [temp limit: 176°F (80°C)]. Hg/Hg2Cl2 is recommended for use in solutions containing proteins, organics, or heavy metals that could react with silver and clog the reference junction [temp limit: 158°F (70°C)].

See here for more info.

http://www.ph-meter.info/pH-electrode-choosing
Heavy metal will react with Ag/AgCl probes they state.

How much or how quick I have no idea.


Dann2

Quote: Originally posted by dann2

Whatever it lacks in content is made up for in the colour scheme.

Quote: Originally posted by Swede

But if the nitrites produce a LESS VIABLE LD coating, then by all means, it becomes yet another issue among so many that must be controlled.

I tried cleaning a small sample of the cheap eBay MMO with Caro's acid, as strong as I could make it, using 1:1 sulfuric plus 35% peroxide.

The original sample had some brown "smut" overlaying portions of the darker MMO. From previous tests, this MMO is excellent for chlorate production, despite the smut and scratches.

The before and after pics, after perhaps 3 minutes immersion:

Before:



After:


The acid did not seem to do much. While the MMO coating itself seemed relatively impervious to the acid/peroxide mix, the smut was not removed, and if anything, it increased slightly. I have no idea what the brown stuff is, but if the use of MMO under lead dioxide bears fruit as an anode, I'd start the procedure with a new, different anode, rather than the eBay stuff so many of us have. The cleaning and prep of the anode is critical prior to plating, and you may as well start with stuff that is new and clean to begin with.

Quote: Originally posted by quest

Hi guys, I was searching the forum for good anode for perchlorate and got up against this thread: http://www.sciencemadness.org/talk/viewthread.php?tid=4177#p... Tacho made a graphite anode using graphite powder and silica gel as a binder, He also mentioned it didn't show any sign of corrosion when used in chlorate cell. Tacho suggested in the thread to try and make a PbO2 anode this way for perchlorate purposes - but I didn't found any evidence for some one trying this in the forum. This thread is from 2005 (4 years ago) so I guess this idea didn't worked. Can some one explain me why the PbO2/SiO2 anode won't work? SiO2 react with what in the "perchlorate cell"? thanks, quest

Titanium cathode embrittlement