Thoughts On Anodes

Thanks for that Sedit,

O well, it's good to clear it up. As someone used to say in my neck of the woods:
"Thinking thought your bum was Castletown"
(Sorry it's a bit rude!!)


I think the Diamonds are some way off for us, perhaps not.
There would be nothing to beat a bit of bling when it come to Chlorate and Perchlorate making!
A good anode for to make Chlorate is the Manganese Dioxide anode. It will last a very long time in a pH controlled cell IMO. It has only been tried in a non pH controlled cell where is lasted some weeks, though the cell went a rather, shall we call it, gay colour.

Cheers,
Dann2

"Thinking thought your bum was Castletown"
(Sorry it's a bit rude!!)


Yehhhh... I THINK I may have been confusing some of the gold perchlorite solutions they used for electrolyts in some papers with gold electrodes.
Oh well happends to the best of us. Either way my statement on using gold leaf to cover carbon electrodes still holds true and I have used them for various applications because of the low corrosion rate and cheap way to gold electrodes.

Are you tracking voltage and current? I hope it's not too early for a congrats on a graphite cell that is clean... hopefully it'll stay that way. Nice job!

Swede

Hello,

I am tracking current (it stays steady at approx. 5.2 amps.) but not voltage. I will start measuring it.
The supply is a computer PSU with Nicrome wire resistor.
After five days the solution is <strike>Crystal</strike> Diamond clear!
If you rub your finger on the anode black comes off.

The amount of acid keeping the pH at 6.9 is now a sensible amount (0.115ml per hour per amp, that 0.6ml per hour going into cell).

I am taking a sample very day so will titrate and get an idea of CE etc. Have no Chloride strips, too miserable to purchase though they would definitely be very very handy.

The cell contains 2 liters of saturated Na Chloride so it should be coming near the end of it's 'run time'.
Will let it run untill erosion starts to show on anode and that will tell me what the Chloride concentration is at the point where erosion starts. Perhaps there will not be a sudden start to erosiong due to low Chloride.
The picture below shows the end of the anode. The corner not in the solution can be seen and it is still sharp like when it started off. The other corner looks eroded a bit, but thats because it is under the solution surface and bubbling, giving visual distortion.

@Swede, have you cranked up a (4 month long run) cell to test the LD on MMO'ed Ti yet?????????????????

Dann 2

LONG LIVE THE POOR MAN'S MMO!


[Edited on 29-1-2009 by dann2]

[Edited on 30-1-2009 by dann2]

Hello Folks,

Some pictures of Graphite Anode from a pH controlled cell. Erosion is low. It is now day 14.
Up a few posts I stated the 'run time' of this cell was about 5 days which was totally wrong. The cell contains approx. 2 liters. Assuming 320grams per liter NaCl (11 moles total NaCl) and I convert all the Chloride into Chlorate at 100% CE then at 5.5 amps that is going to take 13.5 days. If I leave 100 grams per liter Chloride and get 70% CE it will take 14 days.
Anyhow I am taking samples and we shall see later.
You could probable use KClO3 directly from this cell as there would be very little black erosion product.
The solution is not clear. The picture with the thermometer in a jamjar with cell solution shows no black at all while the other picture exaggerates the black hue too much in the solution.
There is very little erosion to be seen on the anode. I intend to let the cell run untill there is alot of erosion on the anode which (I presume) will start to occur when Chloride gets low. Cell temperature is 18C.

Dann2


[Edited on 7-2-2009 by dann2]

Well let me toss it into a beaker full of KCl and see what the currents and the voltages look like... hang on.

Edit: 1 liter relatively weak KCl solution - no "used" liquor. Anode dimensions: 2.5" X 2.5". Cathode dimensions, slightly smaller. Spacing, approx 3/4" or maybe 15 mm.

There is of course massive bubbling and a distinct smell of bleach; a faint smell of chlorine. I will leave it at 4.88V and watch the current, and will reduce voltage only if heating becomes a problem.

I set the supply to constant voltage, and dialing up from 0, here is what I saw...

V------A
0.00--0
1.00--0
2.00--0
2.72--0.10
3.00--0.60
3.30--1.70
3.50--2.50
3.80--3.80
4.88--10.00

I decided to leave it at 4.88V. It started at 10 amps, and over 1/2 hour, it went to 12.1A. Over 1 hour, to 13.6. The amperage is INCREASING at a constant voltage.

I switched the supply to constant current; 13.6A and 4.88V. If the trend of increasing conductivity continues, we should see the voltage DROP. Heating moderate. I have a fan blowing over it and guess the temp to be no more than 50C right now. It is in an HDPE bucket plus a loose-fitting lid. At 13.6A, the smell of chlorine has increased.

So far, it appears to be functioning the same as I would expect any other chlorate-capable MMO. I see no problems... yet.



[Edited on 8-2-2009 by Swede]

Hello Swede,

Have you taken a break

Edit:
Sorry about that. Your post just appeared. Looks like it's good news all around. End of edit.

Anyhow if perhaps the stuff will (god forbid) not pass current it may have a layer of (shall I say) shit on it.
You have suggested this yourself when you could not weld it first time.
Read below, it is from this book
Page 111

Dann2



[Edited on 9-2-2009 by dann2]

casting composition for heater tube thermal link

Results of the cheap eBay anode for chlorate production:

Excellent, approaching spectacular. I am amazed at how much was made, so quickly, in such a small cell. I did no calculations, did not measure chloride, I simply pulled the plug on it when I had to leave town after maybe 2 days.

This was a lowly 1 liter cell, and I started with KCl stock, no used liquor, precursors, or additives of any kind. The current varied between 5 (at night) to 15 max, at which point the 1 quart plastic bucket began to get too hot.

The bottom of the bucket had about an inch of crystals, which I filtered and washed:

I could see no ill effects on the anode mesh. Color variation in this photo are nothing more than a damp, uncleaned anode... it exhibits a typical white smut that cleans off easily.

And the set itself:

Standard Titanium cathode. The efficiency had to be high. I didn't even chill the liquor prior to harvesting. HCl additions were occasional wash-bottle squirts. If you want cheap MMO, that is as inexpensive as I've ever encountered.

Please, no one suggest that it makes perc. I'm not even going to try. If someone wants to know that badly, buy some yourself.

The ONLY drawback I found so far is the odd shape, and the fact that welding it is a bit more challenging, but no big deal. I have come to the conclusion, though, that as cheap as this stuff is, I'd simply cut it in such a way that you don't NEED to weld a shank onto it. Simply cut it into a useful shape and attach your DC current directly to the mesh.

Dann2, how goes the graphite cell?

[Edited on 11-2-2009 by Swede]

MMO MMO MMO MMO MOO!

Hello Swede,

Definitely MMO, no doubt about it.
MMO has come from a difficult to get thing, to being sold on ebay at a knockdown price and under the name of Ti mesh!
The Graphite will have to be renamed very-poor-mans MMO or perhaps Paupers MMO.

The Paupers MMO (PMMO) is going OK. There is little or no erosion visible on the anode though the liquid is getting black. There is actually very little black suspension. Still taking samples and keeping pH at about 7.0. Temp. of cell is approx. 18C. Takes quite alot of acid when it is all added up.
Some phots's below. The jam jar views consist of exibit one with a light behind the jar. The other one (exhibit two), no light behind the jar.
You can see the anode clearly in the other picture. There is very little erosion. There is no noticable thinning or erosion at the water line (not shown in picture).

Dann2

LONG LIVE THE PMMO!!!!!!!

What I am thinking at this point is that if a PVA thickened
hydrosol of peptized hydrated Bi2O3 and SnO2 is applied as a dip and bake coating to the MMO , maybe three or four coats, what will be the result is a perchlorate anode.

See example 1 and 2 of the attached patent US6777477 and modify example 2 following the increase of PVA to 0.87 g as
described for example 7. The level of Bi doping could also probably be raised, perhaps doubled. A very small amount of included Antimony doping on the order of 1/2% to 1% would probably result in a finer grain structure for the baked coating. That should get the job done. This treatment could perhaps be finished by a dip in ammonium fluoride and baking, although this is my speculation concerning the fluoride treatment which should further toughen and dope the coating.

Really this should be done for an oxygen barrier before electrodeposition of PbO2, to change the overvoltage gradient for the coating layers in a way that opposes
delamination of PbO2 by any permeation of electrolyte
which could evolve oxygen at a lower voltage than the
outer surface PbO2, spreading across the interface of
the PbO2 and MMO otherwise to separate the layers.
As the MMO is catalytic it would tend to preferentially evolve oxygen from any permeating electrolyte, unless it has been coated with something like Bismuth or Niobium doped SnO2
in order to raise its oxygen overvoltage higher than the
the overlying PbO2.

Hmmmm, it's just about time for a Valentine's Day
diva break So my fellow estrogen admirers .....
http://www.youtube.com/watch?v=7fpkF31MQ30&fmt=18

http://www.youtube.com/watch?v=XVQcvCfi4G8&fmt=18

[Edited on 13-2-2009 by Rosco Bodine]

Attachment: US6777477 Bi2O3 doped SnO2 via ammonia soluble derivative.pdf (67kB)
This file has been downloaded 587 times

mmo's available via ebay = $39 american

Graphite Erosion

Hello Folks,

Ye old PMMO (Graphite) cell is starting to look like a classic Graphite Anode cell. Jet black electrolyte that you cannot see through even when there is a light behind the cell or container.
Some photo's below. I did not bother with the photo of some of the cell contents in a jamjar with a thermometer (as before) as you cannot see the thermometer at all.
The four samples in the picture below do not tell the whole story as they are being taken from the cell without vigourisly stirring the cell. If I stirred the cell, the last three samples woud be much darker, especially the last one. The first sample would be similar to what you see as there was no black sediment on the bottom of the cell at that time.
Samples are from 9th, 12th, 13th and 15th (February).
The anode has eroded more in the last two days (14th and 15th) than it has in the previous 20. It eroded more in the previous two days prior to 14th and 15th (ie. 13th and 12th) that it eroded in the previous 18.
I think Perchlorate is about to start forming as I can see a greenish efflorescence that you get when there are tiny amounts of Perchlorate when using Methylene blue to detect it. Could be wrong though.
The cell has entered a different 'mode' as I have the acid turned off for the last four days and the pH is staying at 6.7 approx. Temperature is still in the region of 20C.

Dann2

[Edited on 16-2-2009 by dann2]

Hello Folks,

Aqua_Fortis 100% sent me a patent showing how Graphite could be treated with Iron (IRON, FFS ) .
I pasted it here as there is some info. regarding cell voltages in relation to Chloride concentration. I though this might interest yourself Swede if you were trying to link cell voltage with Chloride concentration. The cell voltage does not change very much according to the patent and it would be very temperature dependent. Connections would have to be very very good too.

________________________________
Abstract: (US3632444)

For example, during a comparative experiment employing a normal chlorate graphite electrode with an iron impregnated chlorate graphite electrode, as the concentration of NaCl decreased from about 250 grams per liter to about 150 grams per liter, the cell voltage increased from about 3.25 volts to 3.6 volts with the normal graphite while with iron impregnated graphite, the increase in cell voltage was from about 3.15 to 3.35 volts
__________________________________

Anyhow my Na Chlorate cell registered Perchlorate with a Methylene blue test and I turned it off. That was a few days ago. Still have to titrate contents of samples. I think the Chloride concentration was quite low before the Perchlorate appeared. The anode was eroding at an unacceptable rate.
It eroded more in the last day of operation that in the previous 22 days of operation!

I cranked up a KCl cell using the same anode. I scraped and scrubbed all the loose Graphite off the Anode so it was like new Graphite. Some pictures below. You can see the clean Chlorate but that is only on day three. It will get slightly blacker as the days go by, but not much. I do not intend to run the cell to the Perchlorate point.
The lesson with a Graphite anode is: Controll the pH. In our case this really means adding acid at a certain rate and keeping an eye on pH.
The Chlorate is gathering on the Anode alot. Perhaps I am geting too much 'Anodic Chlorate formation' at the low temperatrue (20C) that the cell is running at.
When starting the cell I measure the pH of the Chloride solution, it was 6.4.
I added 3cc 12% HCl before current was started to give the acid a bit of a head start. This seems necessary from my experince with the Na cell. I also turned acid on at the normal rate. After some hours there was a stink coming from the cell and on measuring the pH it was 0.30.!! Turned off acid for 5 hours and pH was then mearured at 7.6. I decided to add acid to take pH to 6.8 and I had to add 20ml acid (quite a lot) to get pH to 6.8. There seems to be some buffering going on. A very unruley cell!!!!!!!!
The pH stayed at normal value with normal acid addition from then onwards.
It would appear that it is not a good idea to add acid at the start. Just start pump and leave alone.
Dann2

Hello,

Ran the pH controlled K Chlorate cell for 7 days and pulled the plug.
The K Chlorate sticks to the Anode somewhat but it does not seem to be a big problem. Acid addtions seem to be less that an Na cell as I was able to turn off the acid for the last day and a half. Very low acid addition on day 5/6.
Cell was more or less the same as the Na cell above. 20C, 4.5 amps into cell (similar CD).

Extracted the Chlorate by cooling solution and running through a cloth. Most of the black (there was some) stayed with the water leaving the Chlorate fairly clean. You could probably use the Chlorate as it is, though it is off white. In practice you would probably recrystallize to get rid of any Chloride and clean the Chlorate up in the process.
Test for Perchlorate, there was none.

The pH controlled Graphite Anode cell is not in the same league of cleanlyness as an MMO cell but it is not far off! There seems to be more black stuff compared to the Na Cell (at day 7) but that may be because the Anode was used before. There is a picture above of Chlorate sticking to anode. When the Anode was placed back into the cell all this fell off and seemed to take a layer of Graphite with it. There is not much erosioin product though (few grams at most) and whatever was there settled to the bottom of the mother liquor and left a 100% clear solution (for recycling after decanting).

Total weight of product extracted was 422 grams. 842 amper hours into cell gives a current efficiency of (drumm roll) 66%. At least it's better that the Na cell.

I cranked up another Na cell. I insulated (wrapped in swaddling cloths) the cell using tinfoil and fiberglass + polystyrene board underneath. The temperature went to 50C (a bit too high, but I am going to run it at that ). Current is higher because cell is at a lower resistance because of the heat I guess.

Dann2

[Edited on 26-2-2009 by dann2]

Good info and a nice idea. There are a few sources for PTFE heat shrink tubing I've been wanting to tap for some time now, and that would be a good use for them.

I've often thought too about measuring specific gravity of the liquor and seeing if it varies enough during the run to provide useful data. Again, a temperature-dependent measurement, and you'd probably need some VERY sensitive hydrometers or some other method, such as a volumetric flask and a good scale.

I suspect on a streaming chart of cell voltage that you would in fact see a nice "blip" in the downward direction as the acid is injected. Then, the voltage would creep back up to "normal" as the acid is spent in neutralizing whatever species it does.

I'm hard at work on transducers and signal conditioners. It's been a bit trickier than I thought it would, but nothing insurmountable. When the smoke clears, I should have transducers for cell voltage, current, temperature (PT100 RTD for good accuracy, or type K thermocouple), and possibly pH. THAT will be the tough one, requiring clean amplification and filtering to prevent noise from making a hash of it.

We've discussed pH electrodes before in the context of continuous immersion in a chlorate cell (my hypothesis: it will be fatally poisoned in a matter of hours) but it'd be worth a cheap pH electrode or two to see if it does in fact die a quick death.

That lead dioxide anode I made, the good one, is still sitting in its ziploc bag, awaiting testing! I need to finish up the data thing first, then more LD and other anode fun. Question: Do you guys think my LD plating solution will store well? Everything I've read says "no."

Re tentacles: A static potential probably wouldn't be a problem - the input impedance of the meter is high so as long as the electrode can float to the same voltage no current will flow. There's no active electrolysis so the redox potential of the solution is close to 0. In a chlorate cell there's active current passing so an electrode will have a potential gradient across it. That generates a redox gradient which could cause dramatic chemical activity. In either case, if a path exists from the electrode to the power supply connected to the tank and the input impedance of the meter is not high enough (especially through the shield/ground or reference connection), current will flow through the electrode and cause reactions there.

A battery powered pH meter with a very small radius electrode would probably work in an electrolytic cell for a while, perhaps a long while. It probably would last longer if it was well out of the way of the main current flow. Even so, I don't know how well an Ag/AgCl electrode does with chlorate ions (haven't looked it up yet, sorry) or how long epoxy encapsulation would hold up in warm acidic chlorate solution (I know this will eventually destroy it - again, it might take long enough not to matter). The glass part of an electrode would probably be OK.

Anyway, all that is why I'd put my pH probe in a side loop which had very little current passing through it i.e. voltage drop across the loop is close to 0 and either very well isolated from the equipment ground or with a (sacrificial?) electrode connected to the equipment ground near the probes. And I'd try to draw the fluid from a place where the electron flow and ion flow mostly canceled each other.

I have to pay for my electrodes, so I baby them . An old electrode has a good probability of either being unstable or not working at all so getting used ones is a game of chance.

Quote:

Originally posted by densest I have to pay for my electrodes, so I baby them . An old electrode has a good probability of either being unstable or not working at all so getting used ones is a game of chance.

pH controlled Graphite cell contents

Hello,

Took some photo's of the end products of two Graphite Anode cell runs.
The yellow liquid is from the Na Chlorate run. All the Graphite EVENTUALLY settles out leaving a yellow
liquid. In times gone by, there has been many a discussion as to what the yellow may be. Perhaps this explains
it, perhaps not. You don't seem to get any yellow if you do not run the cell untill the Graphite starts to erode at
an unacceptable rate.

I recrystalized the K Chlorate from the next run. It cleans up OK. The mother liquor as shown too. All the Graphite
settles out OK (no yellow). A few grams of K Chlorate needles appeared too. I filtered all Graphite from the K
Chlorate cell and weighted. It came to a (very small) 1.9 grams for the 422grams Chlorate made, which is very
low. There would still be Graphite in the solid Chlorate but it would only be milligrams.
It is a pitb to process K Chlorate that has been made using Graphite. If making K Chlorate use the Na salt
and convert after solution has been filtered. (as many here have said).
If you are happy with somewhat discolored product than it is fesible to go straight with the Graphite I guess in a pH controlled cell that is.

Dann2

[Edited on 4-3-2009 by dann2]

[Edited on 4-3-2009 by dann2]

Nice pics, Dann2. I'm assuming the second pic is chlorate, not chloride... looks like a typo. I think you've shown that decent graphite anodes can make all the chlorate you'd ever need for either pyrotechnic use, or as feedstock. It's odd, with all the chlorate I've made in the last few months, I've always gotten the plate crystal form, never the needle. Even when a solution is slowly cooled, or the conditions are otherwise primed for that form, it never seems to happen. On the contrary, I always end up with pretty massive plate crystals shaped like your second picture.



This was from the 4.4 kg T-Cell harvest, where there was a distinct upper layer, and a much more compact lower layer. I finally figured out what caused this... the lower layer formed while the cell was hot, and actively producing. It was very firm and compacted, and required hammering to break up. The upper layer formed when I pulled the plug, took the rig outside, and cooled the remaining liquor, producing a crystalline fallout.

[Edited on 4-3-2009 by Swede]

Im following in dann2's footsteps with the poor mans MMO until my cheap Ebay MMO comes in the slow Canadian postal system.

Since Im not pH monitoring or controlling, I understand that all the Chlorate made will be by the 9e- process opposed to the bulk reaction. Since this is the case, temperature wont matter too much will it? Unfortunately the only place I could run this cell without (too much) complaint of the Chlorine smell was the back step where the cell has settled at about 0*C.
Since Im not monitoring/recording/calculating anything, I have no clue when it will be close to complete. Any suggestions on when to pull the plug on a ~2.75L cell of saturated NaCl running at ~0.8A and 3.8-4.5V (It appears to be climbing at the limited current) It has been running for approx 27hours.

@ Swede, I hope you have Cold Junction Compensation for your K Thermocouple you are trying to read. And as to our short conversation on pH electrode poisoning; apparently if you have a liquid filled electrode that is Ag/AgCl, you can safely use it with KCl04 if you substitute the solution in the electrode for NaCl or LiCl opposed to KCl. Apparently with KCl, Perchlorate will have the tendancy to precipitate in the junction clogging it (poinsoning). Im still waiting for a reply back to my email requesting more information from the author.

Edit: Bottom left of first picture you can see the fan I removed from the supply that was seized, melted and causing a god awful 60Hz buzz that vibrated the whole unit. Cheapo replacment in the works...

[Edited on 6-3-2009 by pyro6314]

[Edited on 6-3-2009 by pyro6314]

Hello Pyro6314,

Is there a plug on the back of that thing so that you could plug it in a warm it up!!!!!!!!
I like the handle. All the cells I have ever seen they have never had a handle. I guess it has just become a 'must have'.
That cell is going to take a loooooooooong time to finish. The current is very low.
You have approx 15.5 moles Chloride total in cell (900 grams). You will convert approx. 10.5 moles of this to Chlorate. That will take 6 * 10.5 moles electrons which is 6 * 26.8 * 10.5 = 1688 amper hours (100% CE). You have 0.8 ampes going into cell. It will take 1688/0.8 = 2110 hours to finish cell at 100% CE. Thats 88 days. At 50% CE is will take alot more , 176 days to be precise.
Look on the bright side. At least it will be summer time when it finishes.
Put in more amps.
My understanding is that the temperature matters little when you are going the '9 electrons' route (CE 66.66%).
I once knew a guy who did a similar thing out the back in a freezing shed. He got approx. 50% CE in a cold electrolyte (call it the 12 electron route). His gouging rods lasted well too.

BTW:
The table above in my post of 25 Feb showing CE for the pH controlled Na cell is totally wrong. I was having a bad day (another one!) when I calculated that table. I have not got a clue how I managed to come up with the figures in it. I think I forgot to multiply by the amount of liters (2.2) that were in the cell. Will look into it.

The overall CE was 77.7%. Total Chlorate produced was 1278 grams, total amper hours into cell was 2484.
This is similarish to the CE of the next cell I ran (KCl with pH controll, 66% CE) .
The other figures are correct.

Dann2

Pyro6314, that power supply MUST be capable of more than 800 mA! May I ask why you are running it so gently? Is it to try and keep erosion down on the anodes? On that coffee-pot cell, just looking at the size of both the liquor and the electrodes, I'd guess 5 to 10A would be more appropriate.

I know you are working with sodium salts. Dann2 explained the efficiency thing fairly well. For potassium salts, some time ago, I simplified the equations as much as it was possible to do, and came up with this:

***********************************
For Potassium Chlorate Production:

W = Weight of yield, in grams
E = Efficiency
AH = Ampere-Hours used

E = (131.32 * W) / AH

For Potassium Perchlorate Production

E = (38.42 * W) / AH

*************************************

Note that these are "retroactive" equations, meaning you weigh your product, and if you've tracked the AH, you can determine your efficiency. For predictive, IIRC it requires 161 AH per mole Chloride --> Chlorate at 100%. Note that's mole of CHLORIDE ion, not the entire salt, and if you assume 50 to 60% efficiency, you can come pretty closely as to when it is time to yank the plug.

CJC: That little chip has it onboard! It's a wonderful device, essentially a thermocouple meter on a chip. All you need is a good power source and a few supporting components. But when the smoke clears, I doubt I'll be using it, as I'm headed towards a suite of isolated signal conditioning modules, gathered slowly off eBay and other sources. One of them is a PT100 RTD unit that will be more accurate for this sort of thing:



pH: I would LOVE a true pH controller setup, but the calculated dosing technique works very well. It's pretty cool when we have data like "A chlorate manufacturer consumes X pounds of HCl per ton of product" and when scaled down, it does in fact keep the pH very near neutral or slightly acidic. Given the problems of continuous immersion, I doubt I will do anything more than an occasional sample dip with an immediate rinse to keep the precious pH probe healthy. Once the cell is producing, and the acid is periodically added, it seems remarkably stable; I don't remember anything worse than +/- 0.6 swings once it settled down. It seems that the initial startup requires more acid per unit of time than later on, when the bulk process is hopefully taking place. But with no acid - I remember seeing 9 or 10 pH within a few hours of startup.

My graphite electrodes are hopelessly small. Only about 17.1cm2 of anode area in the solution so around 0.7A I figured was ideal to keep about 41mA/cm2 keeping anode erosion at a minimum. Plus at the cells resistance, the current draw topped out at about 1A with 4.3 ish Volts. I'm going away for the weekend so I am going to crank it up to about 5A and leave it. (Probably risky but its outside) I wrapped some old clothing around the pot hoping to insulate it and retain some heat but there is barely any heat running at the small current and the reasonably wide electrode spacing.

Current control is terribly sensitive with a approx 270deg pot divided for 90A. Just touch it for a couple amps. Programming ports on the back will facilitate more accurate control with a resistor bank and pot. Only 100 Ohms full range to control current.

Im looking for a dosing pump/pH controller at present. A Hanna model will do nicely and the combo unit has a provision for manual pump control if you dont use the pH electrode and auto control.

I dont care about my electrodes so Im going to push them hard. If they disintigrate while I'm gone, so be it.

Edit: With two Graphite electrodes, what would an AC current do?

[Edited on 7-3-2009 by pyro6314]

[Edited on 7-3-2009 by pyro6314]

Hello,
An AC afaik does not help. It has been used (making Calcium Chlorate) to keep insoluble hydroxide from building up on one electrode but the 'AC' was more like DC that was reversed every 10 minutes or so.
You would be better off using both rods as anodes and getting yourself some steel wire (or stainless steel) for Cathodes and increasing current.
Put a resistor (piece of Nicrome wire) going to cell to give yourself smoother current control with pot.

Regarding the CE that I reported for my first pH controlled Na Chlorate cell above ran at 20&degC. When calculating CE I forgot to take into consideration of the cell volume. I used Chlorate increase of grams per liter instead of grams increase in the cell.
All CE figures need to be multiplyed by 2.2 (2.2 liters in cell). This now gives very high CE's, up to 90%CE in the middle of the run.
I have just pulled the plug on my latest pH controlled cell ran at approx. 50&degC. Graphite erosion looks similar to cell ran at 20&degC. Looks like low Chloride concentration and high pH are the real Anode murderers. (I was blaming the Butler before this!).


About pH probes in Chlorate cell. The Chlorate manufacturers may not keep their probe immerced 27/7. They may dip them in and out and wash. This would be easy enough to for them to do. It may even be done by an operator. They probably have a known continous flow of acid going into cells (like we do) and if pH goes to drift they stop adding or add extra acid. They would have very detailed knowledge of the acid needed for the cells as they are operated in more or less the same region all of the time. No large Chloride/Chlorate concentration variation for years (literally) on end.
We have a harder task pH controlling our cells because of the way we operate them, (going from 330g/l Chloride / zero Chlorate at start to 80g/l Chloride / ~400g/l Chlorate at the end). The pro's have it easy.
The picture below may be workable. It is more work though. You would need a permanent hole in the Chlorate tank which will not be nice if the electrodes are in the same tank, as the horrible spray will drift out. If a two tank cell is constructed then there would be no spray from the (warm) 'chemical Chlorate formation' tank. If the motor was very weak (small stepper motor) you could forget about the micro switch beside the Chlorate tank as the motor is not going to burn out during the fairly short time that a reading is being taken. Motor output would have to turn fairly slow too.

You are then going to have to time your taking of a reading with the probe in the tank and decide how much extra acid to add for each 00.X amount that the pH is above optimum or how long to turn off acid if below optimum.
All easier said than done!!!

Dann2

[Edited on 8-3-2009 by dann2]

Left my coffee pot 2.75L cell limited at 6V and it will only pull 2.2 A later dropping to 2.0A today. The anode has decreased slightly in diameter. I have salt build up on the top of the electrodes but not much volume drop. Whoever said hotglue wont stand up to the vapors of a Chlorate cell, I have proved you wrong. The glue is still hard and intact. The old sweater used for insulation/snow protection went from black to having a big whitish spot. Since I have no idea of how many electrons have gone into the cell and my guess on how much NaCl was in there is most likely way off, I'm going to run it until my graphite is gone then process the electrolyte. Ignore the PMMO cell...Real (cheap Ebay) MMO is here! Got my new fan the the DC Supply too so that can go back together.



The guy shipped it to Canada for $10US since he cut the length in half. Only one small spot where the coating is wore off (pictured). Anyone have an idea of how to accurately measure/guess the SA of this mesh?

I am not sure but i think that my MMO anode give my perchlorate...

before to make my chlorate cell i read that it is not possible to make perchlorate whit MMO anode but today i read a web page where they were showing the crystal form of potassium chlorate and potassium perchlorate.(http://www.wfvisser.dds.nl/EN/analysis_EN.html) the probleme that at least 75% of the crystal of my cell have the rhombic form, wicht is suppose to be perchlorate...

The problem is that i don't realy want tu have perchlorate for my cell because i am limited whit the use. (no HE mix and not snap bag).


Now that i am pready sure that my anode make kclo4, i have some question:

1. How can i limit the prechlorate formation. (for now i have 2 cell running in serie with a 15V 3A power supplier, they run a 20 C, no ph control, MMO anode (from ebay), stainless stell cathode)

2. how can i be pready sure that it is kclo4 (some test if possible)

I have over 2 kg of this stuff but it is dry and in powder so i need to wait for the next batch to see the crystal(saturday night). i am going to take pic of the crystal and show you the form of the crystal.

[Edite le 11-3-2009 par Bikemaster]

[Edite le 11-3-2009 par Bikemaster]

The space between the electrode is 5 cm.

i find i way to find the the ratio chlorate /perchlorate but i need a better scale (+- 0,1).

but i am pready sure that i have kclo4, because before to have mmo anode i was working with graphite anode and the product reacte not the same. (the one with the graphite anode were much more unstable and reacte more slowly with atomized alluminium powder).

with chance i have and other anode... can i put an other cell to reduce the voltage??? it will be 5v wicth is pready good.

thank for your reply

Ok I just recrystallize roughtly 100g of my last batche.

First, the recrystallize crystal have no more the shape of the precipate in the cell, the crystal have now the square shape, wicth is kclo3.

Secondly, I collect the water of the recrystallization and i boiled down all the water, I collect the salt and i dry it. I mix it with sugar and made the same mix with other of my kclo3 wicth i don't have touch. Result, the mix with the collect salt burn twice slowly that the other mix. So i can say that it have a lot of kcl in it... the inpurity is only kcl and maby 1% are 2% of kclo4 but it dont really change the result of the reaction. i think that i just need to wash the crystal better and it will be ok.


I think that i find the reason why it seem more stable... I feel very stupid but the reason it the shape of the flore... i test the stability of my sample by hitting on it with an hammer. but i don't think about i thing, the type of the flore... before i was testing on rought flore and now i test on smooth flore, wicth is more hard to make detonate.

i find that i had max 3% of kcl in my kclo3 i will only wash them more next time and i think that it will be ok.

thank for helping me

With my current running in my cell so low, only 3.0A @6.0V limited, I decided to put the electrodes closer to try and decrease the resistance....absolutely no difference. I would hazard to guess if I turn up the voltage any more the anode is going to melt off in a big hurry. It already is so I switched polarity. Lol

While I was at it I attempted to filter the graphite out of the glossy pitch black solution (looks like paint) in attempt to reduce erosion...Not going to happen. It clogged my filter paper and majority went through anyways. I did dry out my filter paper and light it There must be an appreciable amount of Chlorate in there already. Topped it up and fired it back up.

I don't have the patience for this icky black mess and I would like the satisfaction of crystal precipitation. My next run will be with KCl and my MMO in the same cell. I will leave dann2 to venture into the black sludge mysteries.

@Swede (or anyone), do you have a suggestion for how big of piece of MMO and how to attach it without access to a spot welder or titanium. Doing this sort of thing without facilities or resources is painful. Maybe I could spot weld with booster cables and my supply @ 90A

Off topic, I'm curious how fast I can vaporize a large chunk of iron into its oxide electrolytically...

Yes, i think that i need at least one recrystallisation. I go over this step because my cell seem clear of impurity but i don't think about kcl... anyway, make one recrystalisation is not very long and it goning to make much better quality kclo3

For you Pyro, i you want to weld something to your mmo anode, you have to think to recoat it, because the spot of titanium will corode it they are in contact with the electrolite. If you want an easy way to hold your anode (if you have mesh anode), use a titanium wire and past it in some of the top hole of your anode. If the titanium wire don't touch to the electrolite, you will never have problem with it.

The pieces I have appear to have been cut with a zip disk or grinder as well. Where the heat would have been concentrated, there appears to be an "alkali" looking white oxidation. Inside the white stuff is silvery stuff with some kind of crystal structure. Man I wish I had Swede's microscope. I emailed the Ebay seller and he says he has 25-35 lbs left and can get more anytime. Such an odd thing to have unlimited supplies of I also asked what its previous application was and what the composition of the MMO is and Im awaiting a reply. I will let you guys know.

As for the "POTENT" vapors... kinda hard to say. Some kind of a crazy replacement reaction with the grinding wheel compound or airborne Ti oxides and MMO. Couldn't tell you. Maybe someone will come up with something after we actually know what its composed of.

For making up an anode, I suppose I could cram a big one into my little cell then just run at a lower current density. No harm in that, correct? When I up size then I can use it there as well. Im waiting for the guy to email me back with me Hanna Dosing pump/ pH controller. Awesome deal if I can get it seeing as the they are in the ballpark of $850 USD retail. (Factor the terrible CAN dollar as well)

Edit: @ Would it be a bad idea to increase the voltage past 6V to get more current through with a graphite cell?
Edit2: He doesn't have any info on the mystery MMO.
[Edited on 13-3-2009 by pyro6314]

[Edited on 13-3-2009 by pyro6314]

Hello Folks,

The latest NaCl cell with pH control, Graphite anode at (approx.) 55&degC finished.
The overall CE was 79%. The end Chloride concentration was 115grams per liter of solution.
Wear on the anode was not too bad. It made the water black but the black settled to the bottom
of the container where the more of the liqued was decanted off. The liquid was clear but has the
yellow colour that seems to always be present with the Graphite anode cells. I had to filter approx.
200ml of black liquiud through the paper filter shown. The Graphite was dried and give a figure of
6.2 grams Graphite per KG Na Chlorate made. This may not be the whole story as some of the
Anode may have gone off as CO2?. I did not weigh the Anode at start (unfortunately).

A total of 200ml of 12% HCl acid was added to the cell.
There does not seem to be a huge advantage in running the cell warm as I did not get a
great increase in CE compared to the cell I ran at 20&degC. It came in at 71% CE and
it was let run untill the Perchlorate point. (low CE at end of 19%).
The 'bucket' type cell design (ie. no design), I guess, has a lot to be disired when you
are controlling pH and have a warm cell.

I have cranked up my old Lead Dioxide Anode (Ti substrate) in a pH controlled cell. It
is going OK for approx. two days. There is alot of the Ti exposed. Funny thing is the Ti
is gassing. The Tin Oxide interface coat must still be there.
This may have been the cause of my low CE in my last (pure) Perchlorate cell using
this Anode. With a large amount of Tin Oxide exposed that would definitely effect CE
as Tin Oxide is a poor Perk. maker. I tried it way back. It just sits there making Oxygen. <br>

Have graph of cell run will post.

Dann2

[Edited on 14-3-2009 by dann2]

Hello Folks,

See graph below for my second pH controlled Na Chlorate cell using Graphite Anode.
The CE's are weird. I have gotton 100% CE between the last two samples. I have rechecked everything. Times, amps maths. I estimated the amounts of Chlorate in the cel by measuring the amount of Chloride and calculating the amount of Chlorate formed from the fact that the starting concentration of Chloride was 300 grams per liter. I did not believe the titrations/CE results so I titrated the samples again for Chlorate this time. Same result so I am standing behind the (rather crazy looking) figures.
I am sorry now that I did not let the cell go on for longer. I though the Chloride was getting low so I pulled the plug.
I need to get a constant current supply. Varying amps is a pitb.
The acid additions you see in the graph is what went into cell. There was no 'extra' additions like my first cell run.
12% HCl btw.
The Cathode area is small with the backs of the Cathodes covered with plastic. (see picture above somewhere).

I came up with a titration for Chloride. It is (IMHO) the best poor man's Chloride titration (PMCT) ever devised. 2 grams Silver Nitrate will do at least 80 titrations. On average the two grams wil probably do 160 titrations. Will not beat Chloride strips on handyness though. See Chloride Titration for info.

See a whopper of a supply on ebay here.
It's in the UK. Not constant current unfortunately but has a variable pot for varying the 3.3 volts out. How much I don't know. Plenty of amps!


Dann2

[Edited on 15-3-2009 by dann2]

400 amp

anode will never resiste to this, no? if I compare with my anode, i need to put 8 of them in parralele if i dont want to destroye them (50 amp max). But for this price, it is a very low price for that much amp.

I have the project to make a big cell (18 L and with 100 amp) and i was thinking about having a ph controle on this cell. If you can give my some idea, tip and think to buy to make a ph controle.
ps. if i can save the most money, it will be fun.

wow thanks, this setting will cost me pready much nothing.

I will use a 2L bottle as a container (100 amp*0.134ml*24h*6day = 1900ml) i have some 1/4 tubing wich can resist to HCL and will finish with and old broken tip pipette (i will reduce the end hole by heating to get the right amount droping per hour (13,4ml).

some question

1.Do the water have the same consistenci that 12% HCl (will be more easy to make my test)?

2.Where do i have to drop my HCl in to the cell? Do they have better places?

3. How can you reduce the amp?with a dimer. But if it is possible, it will be a very good power supply (but better to get 2 because 3.3v it is not a lot)

@Dann2: Beautiful data, well presented and a great analysis. Thanks!

Bikemaster, I think you are confused about current. A simple power supply has two ratings, voltage, and current. Most supplies are fixed voltage. A typical one is 5 VDC. So lets say you have a 5V, 1,000 amp supply, a monster. You hook that up to a toy robot that requires 5V. The supply will not "force" 1,000 amps through the robot. The Robot will function perfectly, and the current will be maybe 1/2 an amp. The 1,000 amp is a RATING, meaning "This supply is capable of delivering 1,000 amps, but only if the connected apparatus will draw it."

Enter ohm's law. If the apparatus has a resistance (all of them do) the RESISTANCE will determine how much current it will draw, according to the following formula:

Current = Voltage divided by Resistance in Ohms, or

I = V/R where I = current. If I hooked a 10 kilohm (10,000 ohm) resistor to the 1,000 amp supply, the current it will draw will be

I = 5 / 10,000 or 0.0005 amps. Not much.

You can manipulate ohms law easily to solve for any of the variables.

A CC (Constant Current) supply is a different beast. Let's say you have a CC supply rated 10V, 100A. You set it up for CC rather than CV, and start your cell. You then dial up 10 amps; the supply calculates the attached load, and determines that 3.6V is what you need, so it delivers 3.6V. Dialing 20 amps, you'd see something like 4.8V. Keep increasing the amperage, and at some point it won't go any higher because you'd be pegged at 10V, the highest voltage it can deliver. If you set 20 amps for a run, you'll see the voltage varying with time as the chemistry of the cell changes. CC supplies are definitely very handy for this process, as you can control heating, and determine CE with ease.

On your cell: If the anode surface is approximately 60mm X 120mm, the cathode the same, and the spacing about 20mm, at 5V you will see that the system will draw maybe 25 to 50 amps, somewhere in that region, depending upon the electrolyte concentration and other factors. For a 50 amp cell, you need HEAVY cables to the electrodes, at least #8, better #6 or #4 copper, or the cables themselves will begin to heat. light cables = bad news; overheating, voltage loss, etc. And the connection to the electrodes needs to be heavy. An alligator clip is a poor choice. A better choice is something like this:



Where I have crimped (you can solder) a heavy Cu lug and bolted it directly to the anode shanks. Look in the electrical section of a big hardware store for stuff like this - terminal blocks, lugs, other good stuff, the type of stuff they use to wire a circuit breaker panel.

A test for an HCl drip with water will come very close. I'd have it drip as far away from the electrodes as possible, and let natural circulation diffuse it throughout your cell.

If I understand your post correctly, you have a 3.3V power supply? If so you are correct, that is a bit on the low side. Power supplies can be used in series with little problem, so two would be 6.6V, a tad high for chlorate, but not bad. I'd NOT use the lamp dimmer - they are designed for 115VAC. not 6.6VDC power. I'd simply open up the spacing between electrodes a bit, make it 50 to 75mm. Do you have an ammeter? If so, fill a beaker with salt solution, power up, and find a spacing that will give you the amperage you desire. A 2L cell is pretty small and will heat rapidly with anything much above 20 amps. You can immerse the bottle in a larger container 3/4 full of water, and position a fan to blow across the water surface, and it will do an effective job to chill the cell. At 10 or 15 amps, it might be OK, but I'd still place the cell in a bucket or something in case of a structural failure - the bucket catches the corrosive liquor.

HTH, good luck, snap a few pics!

I = V/R.... i fell very stupid...

i made over 6 mounth that my cell run and i was not thinking about this...

If follow you, all in these graph is real???
So the the nacl electrolise can give a better yeild because the resistance is always the same?(never precipate) because with the kcl electrosis the resistance increase slowly so we can't put the cell to the max amp possible when we start the cell because the resistance will become to big and the current will no more pass.

thank a lot for those think because it will help a lot. i was not thinking about the size of the wire too...

no i don't have this power supply (400A 3.3v) it was just a question tu now how to control the number of amp passing in the cell. It was just dann2 that want to but this power supply. In my futur cell, i will have approx 100 amps divided on three 2x6 inchs mmo mesh anode. I will probably use computer psu.

I will take picture of the cell contruction, but i want to get the most info as possible before to make it and do full of error. I will probably seed pic of my homemade ph control in less than one week.



[Edite le 16-3-2009 par Bikemaster]

@Dann2, you beat me by moments with that post!

Bikemaster, You've got it backwards a bit - Resistance is the denominator in I = V/R, meaning twice the resistance = 1/2 the current! If you got a better yield than two separate identical systems running at the same time, then something else is at work.

With a (per)chlorate cell there are some fairly simple rules of thumb, and some that are not so simple. With all else being equal, and voltage fixed, and assuming an oversized power supply like our imaginary 5V 1,000 Amp supply...

1) Bigger Electrodes = more amperage
2) Closer spacing = more amperage
3) Higher ionic species concentration = more amperage
4) Heaver cabling and electrode shanks = more amperage, because light cabling causes a voltage loss over a given run, and the longer the cables are, the more loss you have. If you hooked two very long, light wires to your cell and turned it on, then measured the voltage at the electrode shanks, you might measure 4.23. Replace the light wires with short, heavy cables, and repeat, you might measure 4.85. According to I=V/R, if the voltage increases, so does the current. Heavier cabling has less resistance than lighter cabling, and less resistance means more current will flow at a given voltage.

Any time you have heating in your cabling and electrode straps, it's just wasted energy. Barely warm to the touch = good. It's trickier to keep electrode straps cooler because they are usually Ti, and as a conductor, Ti is pretty lame, and heats up, whereas Cu would not.

With potassium salts, as the chlorate falls out, you really don't lose a lot of current, as the liquor is still a wild hash of ionic species like chlorides, chlorate, hypochlorite, and others, and electricity likes aqueous ions... they help current flow. But you do lose some.

It might help you to try some numbers on paper with ohm's law, and do a bit of algebra, and you'll understand the relationship better. You'll get the hang of it. For example, I have no idea of the resistance of my cell at the start, because I have never put an ohmmeter across it, but I can figure it out because I know the other two variables, voltage, and current.

There are three simple variations on ohm's law. We've seen I = V/R. There is also

R=V/I and V = R x I


I set 5 V on my supply and get 45 amps. The resistance is then:

R = V/I

R=5/45

R = 0.111 ohms

If I put two of these cells in series, the resistance would double to 0.22 ohms. Solving for current:

I = V/R
I = 5/0.222
I = 22.5 Amps

Thus the current is cut in half with a fixed 5V supply. Don't get discouraged, the relationship between voltage, resistance, current, and power (watts) can be tricky and confusing.

[Edited on 16-3-2009 by Swede]

oups... all wrong i need to get a good refresh in electric law.

I saw those law 3 year ago and i think that forget some stuff...
For the chemistry part i dont have any probleme... i know what a mole is...

Ok now with the good law: I=V/R

exemple: power supply 15v 3A

I=V/R
3=15/R
3R=15
R=5 ohm
So i need a resistance of 5 ohm to get 3 amp

too much resistance ex:

I=15/30
I=0,5 Amp

smaller resistance ex:

I= 15/2,5
I= 6 amp
but the max amp than we can deliver is 3 amp so it only give 3 amp.

I expect to be to be ok...

i will have have electric and magnetique next session at school so i will be better in electricity

last thing, i need a multimetre,do this one can be good??? wach the spec not the color

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=39001...

i was writing during your post, i don't use 14 gauge wire, i use 22 (speaker cable) and the end these wire have turn to black and the plastic have melt... can be a big lost. i think that i need to get good wire for my next cell.
O wait i have aluminium 6 gauge wire, use for give the energie to a welder, will it be ok.

[Edite le 16-3-2009 par Bikemaster]

Hello,

Sorry about that Swede!

The 'resistance' of the cell is something you cannot really put a figure on as such. If you have a (purchased) resistor, say 20 ohms, it will stay rock steady at 20 ohms (so long as you do not abuse it) as the current and voltage vary. Double Voltage, will double current. Increase Voltag by 10%, current will increase by 10% etc. The resistor is linear, or at lease we are going to use it in its linear region of operation. This is how you use the vast majority of resistors in electonic circuits.
The cell is a beast. Say at 1.4 volts you measure 0.4 amps accross cell, then the resistance of the cell is 3.5 Ohms.
If you increase the voltage by four you will NOT get four times the current. I don't know what you will get but it will be far far more than four * 0.4. Current might increase by 20 amps!. The resistance of the cell is nonlinear.
Try and obtain a constant Current supply, it simplifys things greatly.
I have been getting around to building the Constant Current module shown below (top left of diagram) but have never actually done it. It would be a gread add on for a computer power supply.

There is another wolloper of a supply on ebay.uk here. May be worht the price it is constant voltage out though.

Dann2

Hello Folks,

A guy asked me some time ago via u2u what to do with a heap of Graphite stubs that he could not use. (Sorry I don't remember who but I rubbed out my u2u's.)
Check out below. You could make a Bipolar Electrode array from them. There is no need to actually connect power to the stubs as the current 'jumps' the gap with each stub being an Anode on one side and a Cathode the other side.
You could just hang the stubs from the lid of the cell with cord that would withstand the Chlorate cell conditions if you though the plastic holder was too much bother to make.
For every 6 grams of Graphite stubs you have one KG of Chlorate. (with pH controll).

You can see stuff about the Bipolar electrode array up this thread at posts around 25 and 26 Oct. 2008

Dann2

LONG LIVE THE PAUPERS MMO


[Edited on 19-3-2009 by dann2]