making potassium (per) chlorate

[MrB]

I have plenty to learn about making sodium chlorate and purifying it for use in the perchlorate cells. Folks in the US seldom, if ever, bother with sodium chlorate, and usually make potassium chlorate directly from potassium chloride. This is virgin territory for me, but I hope the learning curve is short.

 

To me, it makes more sense going from potassium chloride to perchlorate, by the route of chlorate, using lead dioxide anodes. It eliminates a bunch of steps, and (in theory) leaves you with a very simple setup. KCl in, KClO4 out. Just apply electricity, and time to make the magic happen. But that's just it. To me, this is something very closely related to black magic. I might be able to repeat the magic chants, and wave my hands in the patterns required, to entice the magic pixies so that they give me some pixie dust, and i think i have a grasp on the basic environmental variables i need to adhere to. You on the other hand, is making your own chant, based on your understanding of the black arts. Which rocks, and i support your efforts with all my best (weirdest, and stupid?) suggestions.

Good luck.

B!

[Arthur]

WSM and a few others understand the chemistry going on, but you don't need understanding to follow the DIY process guide that is his series of articles in PGI mag, the articles usually arrive here on the forum after they have appeared in the mag.

[pyrojig]

What a delight to have great mentors in our midst . It has been such a treat to learn/follow from the foot steps of those who blazed the trail before us.

[WSM]

To me, it makes more sense going from potassium chloride to perchlorate, by the route of chlorate, using lead dioxide anodes. It eliminates a bunch of steps, and (in theory) leaves you with a very simple setup. KCl in, KClO4 out. Just apply electricity, and time to make the magic happen. But that's just it. To me, this is something very closely related to black magic. I might be able to repeat the magic chants, and wave my hands in the patterns required, to entice the magic pixies so that they give me some pixie dust, and i think i have a grasp on the basic environmental variables i need to adhere to. You on the other hand, is making your own chant, based on your understanding of the black arts. Which rocks, and i support your efforts with all my best (weirdest, and stupid?) suggestions.

Good luck.

B!

 

Hi MrB,

 

The only reference I recall was of making sodium perchlorate directly from sodium chloride, and that was using LD coated graphite (GSLD) and a little sodium fluoride in the electrolyte. If I had any GSLD, I'd certainly be up for duplicating their research.

 

Unfortunately, with titanium substrate LD anodes, the fluoride catalyst would damage or destroy the titanium, rendering the anode useless in fairly short order !

 

WSM

Edited March 12, 2016 by WSM

[WSM]

Arthur and pyrojig,

 

Thanks for the kind words. I'm trying to do for others what I wish were done for me; share my experiences and offer guidance in electrochemistry so others can avoid the pitfalls and successfully run chlorate and perchlorate cells without re-inventing the wheel.

 

In this case, your success is my success.

 

WSM

Edited March 12, 2016 by WSM

[WSM]

I just added Part Nine to the Homegrown Oxidizers Blogs. It was originally published in PGI Bulletin number 194, May/June 2015. I think it will be of interest to those wanting to (or hoping to) make perchlorates at some point.

 

We started by using lab grade sodium chlorate and converted it by electrolytic means to sodium perchlorate. The next blog (Part Ten, to be posted later) shows our work in purifying samples of the sodium perchlorate (destroying residual chlorate) and converting it to potassium perchlorate.

 

In the tests performed last year, we exhausted our limited stock of lab grade sodium chlorate (+- 8 Lbs). In order to continue our perchlorate experiments, we've decided to explore manufacturing our own sodium chlorate and comparing it's performance in our perchlorate cells to the lab grade. Also we'd like to see how long the cells will run before either the electrodes fail or we get tired of trying to make them fail.

 

So,... on to sodium chlorate manufacture...

 

WSM

Edited March 21, 2016 by WSM

[Maserface]

Looking forward to it!!

[WSM]

Yesterday, I continued the work on these electrodes and it came together like this:

I found that the thin walled titanium tube made a thin flat end to connect to the electrode. The problem is the material heats too much and too fast when spot welding. My answer to the problem was to back the material with similar stock; MMO ribbon in the case of the anode, and extra CP titanium sheet metal in the case of the cathodes.

IMGP7830.JPG

IMGP7831.JPG

These two photos show the lead tube end sandwiched between the MMO mesh and the MMO ribbon.

IMGP7837.JPG

This photo shows the lead tube end sandwiched between the cathode and a piece of the same CP titanium stock.

I noticed that the thin walled titanium tube was harder to flatten to the point of being completely sealed than thicker wall titanium tubing. When I heat and flatten the tubing, I usually quench the heated end in water and test the closure by blowing through the tube while the end is submerged. If I see bubbles, I reheat, carefully tap the end with a ball peen hammer on an anvil and test again.

With thick walled tubing this completely seals the flattened end, but with the thin walled tubing, no. The fix is to spot weld a row of welds across the flattened end of the tube and Viola, it's sealed shut (air tight).

IMGP7836.JPG

The rest of the photos show the cathode "box" assembly and the finished electrodes together (the anode is wrapped with a paper towel to prevent scratching the MMO surface on the cathodes).

IMGP7832.JPG

IMGP7833.JPG

IMGP7838.JPG

I still need to tin the copper fill rods and fill the titanium tubes. I was waiting to thread the ends of the copper rods but decided to use copper electrical clamps with a spade connection on them which will simplify the power connection to the electrodes without extra work.

IMGP7840.JPG

There's still more to come...

WSM

 

Yesterday I made an attempt to tin the copper fill rods (I coated about 80% of the surfaces, maximum), and tonight tried to set the copper rods in the thin walled titanium lead tubes.

 

I noticed some leaking solder at some of the spot welds and realized I have a problem. I see the thin titanium tubes aren't able to hold up physically as leads. In fact, after spot welding them to the electrodes, the welds are weak points and I was able to break the electrodes off the leads without much force.

 

To save the electrodes, I plan to replace the thin walled tubing material with some thick walled CP titanium tube I have on hand with the same OD as the thin material. I'll use the same procedures to flatten the tube ends, but I shouldn't see any structural problems like with the thin titanium tubing. Filling the thicker tubing leads isn't a problem and I've done it before.

 

I'm glad I discovered this problem before I got much further along and maybe would have wasted some expensive materials.

 

More later...

 

WSM

Edited March 24, 2016 by WSM

[taiwanluthiers]

Do you have a lathe/mill?

 

Was asking because it looks like you may have better luck just taking a CP Titanium rod, and machine a hole into the rod (you will need a lathe for this), then mill a slot into the end to insert your anode. Then you can use the lathe to make a CP titanium bolt which will be used to hold the anode into place (you drill and tap a hole where the slot is so you can insert the bolt). You can then machine a matching copper rod to fit inside that hole inside the rod, with solder to fill any void.

 

This way you have a good solid rod of titanium, with a conductive core inside to make the electricity pass through easily.

 

As for machining titanium, use good carbide tool bit/end mill. I have a mill and I can even machine HSS end mills with carbide end mills (I kid you not... at .01" depth of cut the carbide cuts HSS like butter)

[WSM]

Do you have a lathe/mill?

Was asking because it looks like you may have better luck just taking a CP Titanium rod, and machine a hole into the rod (you will need a lathe for this), then mill a slot into the end to insert your anode. Then you can use the lathe to make a CP titanium bolt which will be used to hold the anode into place (you drill and tap a hole where the slot is so you can insert the bolt). You can then machine a matching copper rod to fit inside that hole inside the rod, with solder to fill any void.

This way you have a good solid rod of titanium, with a conductive core inside to make the electricity pass through easily.

As for machining titanium, use good carbide tool bit/end mill. I have a mill and I can even machine HSS end mills with carbide end mills (I kid you not... at .01" depth of cut the carbide cuts HSS like butter)

 

Thanks taiwanluthiers. I do have a lathe and vertical mill, but no round rod CP titanium between 0.125" and 1.125" OD. Fortunately I do have 0.500 OD CP titanium tubing with a 0.047" wall thickness, which I've successfully used in the past for electrode leads (I wanted to see if the thinner walled material could be used, but am not happy with my results, so far).

 

I still plan to spot weld the leads to the electrodes, and believe they'll work as well as in the past.

 

Thanks for the suggestion, though. If I had 1/2" round CP titanium rod, the whole process would be simpler, if less conductive. We'll see in the future, If I'm proven right or wrong, but for now I'll keep trying with the titanium tubing.

 

WSM

[WSM]

The main problem I see with the thin walled, CP titanium tubing, is the wall thickness is only 0.020" (0.508 mm) and when spot welded, is compromised to where leaks have formed (definitely not good).

 

The other 0.500" OD CP titanium tubing I have has a wall thickness of 0.047" (~ 1.2 mm) and I've successfully used it in the past, but have a limited supply of the thicker tube.

 

I plan to use it for my sodium chlorate cell experiments, so it's worth using it in this case.

 

As always, more to come...

 

WSM

[taiwanluthiers]

Are CP titanium round bar just hard to come by? I notice vast majority of the titanium out there is 6AL4V... and it makes a HUGE difference in terms of survivability in a cell. I'd like to get some titanium to machine around with but they seem hard to find, especially grade 2.

[WSM]

Are CP titanium round bar just hard to come by? I notice vast majority of the titanium out there is 6AL4V... and it makes a HUGE difference in terms of survivability in a cell. I'd like to get some titanium to machine around with but they seem hard to find, especially grade 2.

 

CP titanium round rod isn't hard to come by; I just haven't collected much. Grades 1, 2, 3, and 4 are four of the common CP grades, and useful for electrodes.

 

The alloys (6AL4V, for example) are less useful for electrodes and may well introduce unwanted ions to your electrolyte.

 

If you PM me, I can send a link to sellers online.

 

WSM

Edited March 26, 2016 by WSM

[Mike]

Don't use grade 5, unless you want to recycle the cell liquer after a couple runs to get your electrodes back.

[WSM]

Don't use grade 5, unless you want to recycle the cell liquer after a couple runs to get your electrodes back.

Also, machining it is a lot tougher. It makes nice sparks, though.

 

WSM

[WSM]

Thanks taiwanluthiers. I do have a lathe and vertical mill, but no round rod CP titanium between 0.125" and 1.125" OD. Fortunately I do have 0.500 OD CP titanium tubing with a 0.047" wall thickness, which I've successfully used in the past for electrode leads (I wanted to see if the thinner walled material could be used, but am not happy with my results, so far).

I still plan to spot weld the leads to the electrodes, and believe they'll work as well as in the past.

Thanks for the suggestion, though. If I had 1/2" round CP titanium rod, the whole process would be simpler, if less conductive. We'll see in the future, If I'm proven right or wrong, but for now I'll keep trying with the titanium tubing.

WSM

 

I was wrong. The thick wall 1/2" OD titanium tubing I mentioned has a wall thickness of 0.065", so the ID is 0.370". All of my titanium stock is CP grade, except for a small sample pack of bolts which are all alloy (too bad ).

 

The 3/8" OD titanium tubing I have has a wall thickness of 0.042" and an ID of 0.291". I've purchased a length of pure copper round rod that is 0.250" diameter to use as filler rod in the 3/8" titanium tubing.

 

I estimate the current carrying capacity of 1/4" copper rod as about 95 Amps, minimum. Since I'm running the large sodium cell at half that (~44 A), I don't foresee any serious heating issues as a result.

 

WSM

[WSM]

Happy Easter

 

 

The main problem I see with the thin walled, CP titanium tubing, is the wall thickness is only 0.020" (0.508 mm) and when spot welded, is compromised to where leaks have formed (definitely not good).

The other 0.500" OD CP titanium tubing I have has a wall thickness of 0.047" (~ 1.2 mm) and I've successfully used it in the past, but have a limited supply of the thicker tube.

I plan to use it for my sodium chlorate cell experiments, so it's worth using it in this case.

As always, more to come...

WSM

 

Since I broke the electrodes off the compromised thin-wall 1/2" OD titanium tubes (which was way too easy to do), I spent the time and replaced them with thick-wall 3/8" OD titanium tubes.

 

Here is the size comparison

 

First I heat and flatten the ends. The nature of titanium is it tends to work harden so I go through several cycles of heating and forming before it's done.

 

 

Next I buff off the scale.

 

 

Now it's time to spot weld the tubular leads to the electrodes.

 

 

 

 

The failure of the thin-wall tubing was a minor setback and a learning experience.

 

The next step is to fill and finish the leads, modify the PVDF compression fittings and mount the electrode assemblies in the lid of the sodium chlorate cell, preparatory to running it.

 

There's lots more to do, but it's coming along and should be running fairly soon.

 

WSM

 

 

 

[WSM]

Rather than have the end of the copper fill rod longer than the cavity inside the titanium leads, and clamp power leads to the exposed end of the copper rod; I've threaded the top ends of the 3/8" CP titanium lead tubes. Using a special tap designed for use with titanium, I cut 5/16" course threads in the 3/8" titanium tubes and use 3/4" long brass hex bolts with a pair of brass washers to hold the ring terminal from the power lead.

 

tapped titanium tubing

 

Assembled brass termination

 

The tricky part is getting the length of the copper fill rod just right where it is tightly held between the bottom of the titanium tube and the end of the brass bolt, all while still tightly clamping the power lead ring terminal. This is important because a loose fit would lead to wasted current and heating, which could damage the polymer compression fitting holding the electrode leads in the lid of the cell.

 

The next step is to acid treat the spot welds on the electrodes to remove any contaminants before using them in an active cell. I've noticed small bits of copper from the spot welder tips sometimes get left in the spot weld on titanium. If not removed, they could form some dangerous, sensitizing copper chlorate contamination in initial chlorate runs of the cell.

 

We eliminate this possibility by soaking the spot welded parts of the electrodes in full strength muriatic pool acid (31.45% HCl) which I've calculated to be 10M HCl. After about an hour, the copper is reacted (plus any react-able smut on the surplus MMO) and it is washed away with a pure water rinse.

 

The MMO is unharmed by this treatment and is left clean for our electrochemistry work.

 

WSM

[WSM]

I've managed to treat the electrodes with HCl for about an hour each, rinse and dry them. I believe any copper or other contaminant of concern is neutralized and washed down the drain.

 

I've also managed to mount the now finished electrodes in the lid of the cell and stabilize them with stiff pieces of Teflon tubing so they are less likely to electrically short out by bumping together.

 

 

As seen I've drilled and tapped several 1/2" NPT (National Pipe Taper) holes in the lid of the cell to attach the electrodes, a vent and several other things which I'll explain later as I progress the job.

 

 

I've begun to plumb the cell and need to add some sensors to the cell through the fittings I've placed in the cell lid. I hope I can get this cell up and running soon. I don't expect any product till after the second run, because of the highly soluble nature of the sodium chlorate I'm making.

 

Much more to come...

 

WSM

[solkompleksowa]

I've managed to treat the electrodes with HCl for about an hour each, rinse and dry them. I believe any copper or other contaminant of concern is neutralized and washed down the drain.

 

Copper won't dissolve in HCl (CuO will) because HCl is a nonoxidative acid. HCl + H2O2 will, so may try this out to be 100% sure there is no metalic copper left.

[Mumbles]

HCl and H2O2 make a pretty nasty concoction when mixed together, making hypochlorous acid and chlorine gas. I would be concerned about it attacking the titanium or anode material in addition to any trace contaminants. It is known that HCl soaks can clean up anodes. Whether it also can remove copper is another matter. If copper were a concern, I'd look toward dilute nitric acid before hitting it with a sledge hammer like HCl + H2O2.

[Arthur]

If the surface is smooth then a rub with brass polish will show and abrade any brass or copper.

[WSM]

Copper won't dissolve in HCl (CuO will) because HCl is a nonoxidative acid. HCl + H2O2 will, so may try this out to be 100% sure there is no metalic copper left.

 

According to the CRC Handbook of Chemistry and Physics, copper is listed as soluble in HNO₃, soluble in hot H₂SO₄ and very slightly soluble in HCl. I suppose dropper application of nitric acid on the spot welds would dissolve any copper left, and shouldn't cause MMO any problems (according to Swede, anyway).

 

WSM

[WSM]

HCl and H2O2 make a pretty nasty concoction when mixed together, making hypochlorous acid and chlorine gas. I would be concerned about it attacking the titanium or anode material in addition to any trace contaminants. It is known that HCl soaks can clean up anodes. Whether it also can remove copper is another matter. If copper were a concern, I'd look toward dilute nitric acid before hitting it with a sledge hammer like HCl + H2O2.

Thanks, Mumbles. I think even full strength nitric acid might be okay. I'm considering using a dropper to apply it just to the welds, to save on the limited resource it is in my stocks.

 

I wonder if treating the copper contaminants with 30% H₂O₂ and rinsing with pure water would oxidize the copper to copper oxide? If so, then treatment with HCl might work to remove the last traces?!!

 

Another thought might be to try Aqua Regia if it wouldn't dissolve the MMO or some of it's major components.

 

Nitric acid seems to be the best approach.

 

WSM

Edited April 17, 2016 by WSM

[WSM]

If the surface is smooth then a rub with brass polish will show and abrade any brass or copper.

 

Unfortunately, the spot weld leaves a pit reminiscent of a Moon crater. That, and the MMO really doesn't like being abraded (though it does tolerate acid treatment pretty well).

 

WSM