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Author: Subject: Tutorial for making a miniature chlorate cell
woelen
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[*] posted on 24-9-2010 at 13:36
Tutorial for making a miniature chlorate cell


Quite a lot of tutorials are present on the Internet for building chlorate cells, using all kinds of anodes and all kinds of big containers for making hundreds of grams per day or even almost 1 kilo per day. That kind of cells are big, need a power supply capable of delivering tens of amperes and need big MMO anodes and equally big cathodes.

For the home chemist, who just wants 50 to 100 grams of KClO3 for nice fire-demos or small-scale syntheses the construction of those big cells may look rather intimidating.

I made a very small 100 ml cell, which allows one to make 30 grams of KClO3 per day and which can be operated from a simple fixed 5 volt power supply, which only needs to be capable of delivering 5A (the cell itself takes only 3 to 4 A, but using a 5 A power supply gives some headroom and allows for tolerances in construction of the cell). Cost of the cell only is $30, excluding the power supply.

http://woelen.homescience.net/science/chem/exps/miniature_ch...

The potassium chlorate, obtained from this cell is perfectly white, it really is white like snow. For making this cell, I used specially made anodes, made by our own sciencemadness member Swede. See the webpage for more info.

[Edited on 24-9-10 by woelen]




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[*] posted on 24-9-2010 at 13:56


Link to the actual project page: http://woelen.homescience.net/science/chem/exps/miniature_ch...

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[*] posted on 24-9-2010 at 14:32


Great article! Its a shame about the bromate not working.

I am going to try making a chlorate cell this weekend using a normal scale eBay anode.




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[*] posted on 25-9-2010 at 02:46


The electrodes are critical and Swede has done lots of research into materials sizes and types to get good cell performance. He has shared his research so please don't waste the shared wisdom.

Some people found that glass containers were not best suited, and also found that power supply interruptions were very bad for the cell integrity. However this was found in larger cells running 50 to 100 amps into a large enough cell to run around the 75C mark.
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[*] posted on 25-9-2010 at 09:54


Power supply interruptions for longer time indeed are very bad. A short interrupt for a few tens of seconds for topping up liquid level does no real harm, provided one uses titanium cathodes.

I did not know of the problem with glass. I myself don't have any problems with this, but I'll change the page and mention the problem with glass when larger cells are used. I'm quite sure this has to do with high pH, which leads to dissolving some of the silicate in the glass, which can settle at the electrodes. I, however, never allow my electrodes to get dry. I take them out of the glass jar and immediately transfer them to a beaker full of tap water. That probably greatly helps preventing the buildup of a silicate layer on the electrodes.

I also did another experiment. I have been running the cell, but now without any cooling. The glass container became so hot that I could not bear touching it. But the current efficiency is better. Already 18 hours after power on, there was a quick transition of just a little oxygen production at the anode to very fast oxygen production at the anode. This means that almost chloride has been used up at that point and that the cell simply decomposes water (MMO anodes don't make perchlorate, they simply make oxygen at the anode). In order to test my hypothesis I added a few grams of KCl, dissolved in a few ml of boiling water. Almost immediately after adding this KCl, the production of gas at the anode ceased, until after an hour or so the production of gas at the anode was quite fast again.
So, running the cell really hot is tempting from a point of view of current efficiency, but it also puts more strain on the anode and the overall cell construction. For next runs, I'll use some cooling again, I just did this single experiment to see how much of a difference it makes.

[Edited on 25-9-10 by woelen]




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[*] posted on 25-9-2010 at 10:55


Now I know this is not directly related, but it is similair and does not deserve its own thread. Regular bleach is about 5% NaOCl and often times has detergents mixed in, and pool chlorinator is usually about 16% NaOCl with lots of impurities. And as you all know electrolysis of NaCl solutions first forms NaOCl which dissasociates into NaClO3 and more NaCl. So I am interested in modifying a chlorate cell to produce concentrated NaOCl solutions. How would I go about doing this? Would simply keeping the solution cold produce hypochlorite, or are there other factors? I have made a few pounds of sodium and potassium chlorate from a Co3O4/NiO coated Ti anode, but I am not quite sure how to produce the hypochlorite alone.

Oh and the reason why I am asking, is I plan on using the hypochlorite for various organic oxidations as it seems to be cheap and has good yields.
Thanks!
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[*] posted on 25-9-2010 at 11:39


The web page is updated. The remark of Contrabasso on the use of a glass bottle is put in the webpage and also the results of the third run without cooling are mentioned in the webpage.

@mnick12: I do not think that making hypochlorite is possible by simply keeping the cell cold. As I wrote in my webpage, when the hypochlorite cannot be converted to chlorate in the liquid (either by low temperature, or by too high pH), then hypochlorite ions are oxidized to ClO radicals and these recombine and react with water to give chlorate, chloride and oxygen. So, when you keep the cell cold you also get chlorate, albeit at a lower current efficiency.

If you really want to make hypochlorite of decent purity, then I think that a much better way is to bubble Cl2 through a solution of NaOH until no more Cl2 is absorbed. For stability you then can add a little amount of NaOH again in order to bring up the pH, such that all hypochlorite is present as ClO(-) and not as HOCl.






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[*] posted on 26-9-2010 at 21:23


I discovered the same problem with bromate. I once attempted to use a platinized titanium anode, which promptly resulted in a large mess of white goo.

Tim




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[*] posted on 27-9-2010 at 07:30


Ten years ago I made some KClO3 with success from diet salt (2 parts KCl + 1part Nal), it is rather pure.
See on www.metallab.net/KClO3 .
But thiis method without carbon anodes will be better.

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[*] posted on 27-9-2010 at 11:04


The industrial process for Perc is in two parts, First the chloride is electrolysed to chlorate, this is then purified. In a separate cell chlorate is electrolysed to perchlorate using precious metal electrodes. Think big batches and very big currents!
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[*] posted on 18-10-2010 at 01:48


Last weekend I used my miniature cell for making CsClO3. The key to success with CsClO3 is not to use too concentrated solutions.

CsClO3 can be made from CsCl just like KClO3 can be made from KCl. With KCl you have to make a more or less saturated solution, with CsCl that will lead to coverage by crystals and blocking of the electrodes.

A good concentration is to take 40 grams of CsCl and dissolve that in water, such that 100 ml of solution is obtained. This solution can be electrolysed until the current drops to just a fraction of the initial current. At that point more than 90% of all CsCl is converted to CsClO3.

There are more differences with KCl. You cannot simply add some K2Cr2O7 to the solution of CsCl. It gives a nasty sticky precipitate of Cs2Cr2O7, which does not dissolve. Instead, you must dissolve just a tiny amount (e.g. 20 mg) of K2Cr2O7 in a few ml of water and add this solution to a hot solution of CsCl and stir. The resulting liquid then is yellow.

The following procedure can be used to make CsClO3. I have done it a few times and it works like a charm:

- Take 40 grams of CsCl and add 60 ml of very hot water. Dissolve all of it and if necessary, filter the solution.
- Dissolve a tiny amount of K2Cr2O7 in a few ml of water. Bring this to a boil.
- Add the boiling hot solution of K2Cr2O7 to the hot solution of CsCl and stir.
- Top up to 100 ml and stir to make the solution homogeneous.
- Start electrolysis and measure the starting current.
- Assure that the cell remains rather hot. If the electrolysis process does not provide enough heat, then use external heating. However, usually the process provides enough heat from itself.
- Keep on electrolysing until the current has dropped to just a fraction of the starting current. This may take a long time, depending on the initial current. At a current of 1 A this may take two full days. During the process it might be necessary to top up the cell with hot water. Only do this when the volume drops below 80 ml. Then top up to 90 ml.
- If no external heat is applied and the cell runs sufficiently hot from itself, then you can also notice the end of the process by cooling down of the cell.
- At the end of the process there will be a lot of crystal mass at the bottom.
- Disconnect the electrodes and allow the cell to cool down slowly to room temperature.
- After cooling down, put in the fridge to allow further cool down to 0 C or even colder (but it should not freeze).
- Decant the yellow liquid from the crystal mass as good as possible.
- Take a heap of paper tissue and put a coffee filter on it. Put the crystal mass on the filter and allow liquid to sock in the filter and paper tissue. Repeat this step one or two times.
- Recrystallize from 50 ml or so of boiling water. Assure that ALL crystals dissolve. Add portions of 10 ml of water until all crystals have dissolved.
- Allow to cool down, decant liquid, make dry on filter paper and tissue, and then rinse with ice cold water and dry another time on a fresh filter and paper tissue.
- Give a final dry at a warm place for one day (e.g. on a heating radiator for one day).

Yield of this procedure: 80%, based on CsCl, approximately 40 grams of CsClO3.

If all the rinsing water and the yellow liquid are kept, then the Cs in that also can be recovered partially. In total, I had 140 grams of CsCl available for this experiment. I made 145 grams of CsClO3 from that and from all the rinse water and so on, I also recovered approximately 20 grams of CsClO4 (by treating that with a solution of NaClO4). So, in total I lost approximately 10% of all Cs, most of that being lost in the coffee filters and the liquid, absorbed by the paper tissue. It is fun to let the coffee filters dry and then light them with a cigarette lighter. The burning of the coffee filters is quite spectacular :)

[Edited on 17-4-12 by woelen]




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[*] posted on 18-10-2010 at 08:02


How's the flame color, do we get a video?



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[*] posted on 8-11-2010 at 05:29


I tried making a video of the burning of a mix of CsClO3 and sulphur and also one of burning a mix of KClO3 and sulphur. The resulting video is disappointing and does not render the nice colors which I can see. The flame simply is over-exposed and white. I'll have to wait for a bright day and make a video on that day. My problem is that the camera takes average brightness and while the background still looks OK, the flame is way too light. Unfortunately, over here the days are very short now (I go to work in darkness and come home in darkness), so the bright day must be a weekend day.

The flame color of a CsClO3/S mix is blue/purple. It is not purely blue. The flame color of a KClO3/S mix is more pinkish, but it also depends on the amount of sulphur in the mix. When excess sulphur is used, then the color is more blue.

My idea is to make a mix of CsClO3 and S and a mix of KClO3 and S. Then CsClO3/S mix is put in the form of a line (5 cm length, 5 mm width) and adjacent to this the KClO3/S mix is put in the form of a similar line. Then I light the total line on one side. Then you first see the color of the burning of the CsClO3/S mix and then you see that color change to the color of a burning KClO3/S mix. I also might add a line of Ba(ClO3)2/S mix to this (my next project is making Ba(ClO3)2 from BaCl2, I am in the process of acquiring appr. 1 kilo of BaCl2).

[Edited on 8-11-10 by woelen]




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[*] posted on 8-11-2010 at 10:37


It might help to burn the compositions in front of a white screen, to reflect the light and brighten the scene.

Tim




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[*] posted on 14-8-2011 at 07:41


Sorry to revive this antique thread but I have a question for Woelen about the material used for this cool cell project.

Being a cheapskate, I was wondering about the Titanium / MMO electrodes. I have secured a good-sized sheet of metallic titanium (top cover of an old G4 powerbook). So my titanium cathode is good to go.

Now about the MMO anode, could I use instead Platinum wire? I happen to have two spools of "Platinum alloy" wire and was thinking of wrapping a lenght of it on a glass canule...

I imagine that the reason Titanium isn't used as the anode material is that it's attacked by the electrolysis and generates Titanium Chloride?

And if I recall, carbon anodes are very good and inert but have this unfortunate tendency of slowly disintegrating and mixing carbon residue and bonding agents with the resulting chlorate...

Anyway, just a few vague questions on the anode material. I was thinking of trying out this experiment and since I have a fair amount of Ti and a good power supply, my last hurdle was to find an alternative to the purchase of a ready to use mixed-metal-oxide anode.

I have about 400 g of Potassium Chloride to use in my future cell so I have many of the main ingredients to get this project going.

Robert




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[*] posted on 14-8-2011 at 14:00


arthur i know you summoned woelen in specific but i think titanium as an anode just stops conducting altogether after a while.nurdrage does that mmo with the stuff made from battery crud. i have gotten as far as making the battery crud manganesee sulfate stuff but stopped because i still needed cobalt nitrate for the first coat.you got two spools of platinum wire? wow i wouldve tried it out with a two inch piece for sure and i'm sure that even though its platinum alloy its still expensive. i also think i will invest on some mmo electrodes or plated ones. well i will wait on woelens response to you as well.

[Edited on 14-8-2011 by cyanureeves]
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[*] posted on 14-8-2011 at 14:34


I've never had a problem filtering out the carbon crud from gouging rods. Each lasts many dozens of hours, or hundreds. Maybe I'm missing something but graphite rods are the perfect solution for a HC who wants to make chlorate on the cheap, seems to me.

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[*] posted on 14-8-2011 at 17:00


hey tank.i am using carbon rods from a 6 volt battery but i saw some graphite rods on ebay and thought about buying one . are graphite rods way better than the carbon rods? i googled how to make chlorate and a fella there called 6volt battery rods, graphite. this is not correct is it?
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[*] posted on 14-8-2011 at 18:42


Reeves, I've never tried with battery carbons. I use 'graphite' gouging rods although I think that's also a misnomer. By my eyeball, they seem to be a mixture of graphite, carbon, probably clay and who knows what else. I can make 'pencil' marks on a rough surface with some difficulty. They even hold up pretty well in my sodium cells (consumable item).

Check your local welding supply stores to see what sizes and pricing they offer. Virtually all have copper cladding that's easy to remove in a dummy chlorate cell. Again, the little bit of stuff that does shear off is very easy to filter with frit or similar.

Real graphite is very soft and easily marks almost any surface. I can't say from experience if these graphite rods provide any real advantages over gouging carbons. If the price is right, go for it.

Tank
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[*] posted on 15-8-2011 at 05:32


Quote: Originally posted by cyanureeves  
.........battery crud. i have gotten as far as making the battery crud manganesee sulfate stuff but stopped because i still needed cobalt nitrate for the first coat........
[Edited on 14-8-2011 by cyanureeves]


You don't need Cobalt Oxide (from Cobalt Nitrate) as a first coat. Mn Oxide on it's own is fine. The Cobalt Oxide may even be a disadvantage. Cobalt Oxide lasts only a short time in a Chlorate cell, even less time in a Perk. cell. Use any spare money, time or energy that you may have putting on extra MnO2 coats.

Dann2
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[*] posted on 15-8-2011 at 14:25


thanks tank, thanks dann2.
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[*] posted on 16-8-2011 at 03:22


I do have some graphite rods (I picked-up a box when I was a projectionist at a movie theatre) so I might try to use the combination of a Titanium cathode and a Graphite anode.

As for the container, I was thinking of using Silicone caulking to seal the electrode contacts and the glass vent tube on the top cover for a really airtight container and drive the resulting gases through a vinyl tube. Has anyone tried Silicone caulking, the bathroom tile joints kind? Does it resist the temperatures generated by the cell?

The cool part about graphite rods instead of carbon battery rods is that these graphite rods are extra long and when one starts to shorten because of degradation, you just push it a little further down in the solution. (the principle of the carbon arc light in these antique movie projectors, except it was a notorised insertion system that slowly pushed the rod for optimal arc).

Of course the platinum wire would be best but i've been scratching my head as how to use it effectively in a cell by wrapping it around something inert and heat-resistant.

Just thinking aloud. it would be great if I could use the materials I have at my disposal, it's just a bit of mechanical engineering I have to come up with...

Robert


[Edited on 16-8-2011 by Arthur Dent]




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[*] posted on 16-8-2011 at 09:12


Quote: Originally posted by Arthur Dent  

Of course the platinum wire would be best but i've been scratching my head as how to use it effectively in a cell by wrapping it around something inert and heat-resistant.



Scroll down to the section on electrodes
http://woelen.homescience.net/science/chem/exps/KBrO3_synth/...
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[*] posted on 16-8-2011 at 19:00


Robert, I've had good results with rubber grommets. If you want to mechanically fix the electrodes to the cell, liquid nails is the best I've used so far. JB weld (actually, most 2-part epoxy) won't stick worth a damn to plastic unless it's pre-conditioned.

If you keep the temp, pH, chloride, etc. in check, your gouging rod(s) will complete several batches without having to readjust the depth. I rigged up a crude electrolyte drip delivery system and it worked great at keeping the cell running at optimized levels.

The crude liquor looks like crap but once run through a fine frit filter, you have crystal clear, yellow-tinted Chlorate liquor ready to convert to potassium chlorate (if desired).

Must be nice having platinum wire at your disposal. :D

Tank
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[*] posted on 29-8-2011 at 17:43


dann2 is manganese dioxode really enough and no need for cobalt nitrate? i would rather bake the manganese on than electroplate the anode because nurdrage's flaked off.
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