21st February 2010 04:53

SilentPro wrote...

To Larry's idea:

Some people tried to applicate that thermal method, but as Alan already wrote it's too dangerous for larger scales. Since an early accident in 1899 (big fire at factory storing big amounts of KClO3) it's proven that molten KClO3 is explosive without any organic additive and can be initiated from hot spots.

It's also possible that a contermination with dust or something else could start a reaction.

You also lose min. 50% of your chlorate and have to separte chloride, perchlorate and left (traces of) chlorate. Not less laborious than per electrolysis!

To this article:

The experiment is indeed quite a few years ago, but seeing you answering to recent comments make me believe, that you're still a bit interested in this topic yourself. Although you stopped experimenting on per-/chlorates. I think i'm quite into this topic as well (and still at this moment) and studied all sources in the web and also some in literature and patents.

So I'd like to add something to your comments to the experiment. Although this small scale test cell wasn't meant to run efficently, there are at least a few mistakes or negligences in the design.

1. You didn't prevent reduction at the cathode.

Normally (industrially) chromates are used as additives to coat the cathode with an oxide layer, that inhibits cathodic reductions.

I hear a lot, that some non-chemist folks dislike the usage of that cancerogen compound, which is comprehensible. But in earlier times other, simplier additives were used with nearly the same effect. Among that were Ca- and Mg-salts that form insoluble hydroxides at the cathode. Those additives shouldn't disturb the electrolyte processing steps or can be seperated as sulfates if nescessary. Apart from that is chromate the main key for bigger efficiencies. pH, Temp., current density can be neglected by hobbyists, but cathode reduction is significant.

2. As your "electrolyte processing" and "math" sections revealed, you were already producing perchlorate.

Your yield of chlorate shows that max. 100 g/L chloride were left, which is the prerequisite for perchlorate formation. So it's not the fault of the platinum you used, but the long time you kept the cell going.

As long as you stay above 100-150 g/L chloride you can produce perchlorate-free chlorates.

Best you would resaturate with chloride from time to time and let the chlorate precipitate from the saturated cell liquor (outside). Also good practice with sodium chlorate to obtain an chloride free product (for perchlorate electrolysis).

3. The use of platinum wire is not advisable, as you have told already.

If you apply it as described, you can only take advantage of a few centimeters of the wire. That is because the specific resistence of platinum is very high. The wire cannot deliver the big currents used to distant parts of the wire and so the current density drops fast under a level that's needed for chlorate formation. As seen at another article the rest of the wire becomes coated or even corroded during electrolysis if no sufficient current flows through it. If you want to use wire, than don't use a big strand but several short parallel strands connected to a copper wire. But that could be hard to be sealed in a glass container.

22nd January 2010 01:36

Alan Yates wrote...

Larry,

I haven't tried the thermal auto-oxidation method to generate Perchlorates from a Chlorate, at least not at a large scale. I have held Potassium Chlorate molten in a test tube for an extended period and it does seem to fizz a bit and eventually solidify before melting again with more heat - suggesting the method might work.

For making Chlorate I'd suggest you don't waste Platinum anodes and keep them for making Perchlorate electrolytically. Graphite will work just fine for making Chlorates, but you do need to filter out the mess at the end. The toaster oven is probably not quite making the melting point of Potassium Chlorate. 450 F is about 232 C. The melting point is 356 C or 673 F.

This method has always struck me as risky anyway. Large quantities of molten Potassium Chlorate are pretty dangerous. Any contamination would be very likely to cause a run-away decomposition and perhaps a violent explosion.

Regards,

Alan

20th January 2010 03:08

larry wrote...

I built a cell with a platinum coated anode. From a saturated solution of potassium chloride it seems to produce mostly potassium chlorate which I would like to convert to perchlorate. I've read article that suggest heating the chlorate in a toaster for several hours at just above "melting temperature". I tried this and the crystals don't seem to melt at the 450 degree (F) max temperature of the toaster oven. Any suggestions?

28th June 2009 12:13

Alan Yates wrote...

Wes,

Yes, Perchlorate is ClO4-.

I didn't run this particular cell long enough to convert the majority of Potassium Chlorate to Potassium Perchlorate. It was a run to just generate Potassium Chlorate. Although later tests indicated there was a bit of Perchlorate generated even in these non-optimal conditions.

Running a cell with a Pt anode on Potassium Chloride will produce some Perchlorate, but not much as the solubility of Potassium Chlorate is fairly low. Do so is inefficient and hard on the anode. If you want to make Perchlorates it is best to start with fairly pure Sodium Chlorate in your Perchlorate cell. You can make Sodium Chlorate from salt using cheaper anodes like Graphite. It is possible to run from Sodium Chloride right through to Sodium Perchlorate but anode wear increases as the Chloride concentration drops and Perchlorate production is very low until most of the Chloride is gone.

Regards,

Alan

27th June 2009 23:51

Wes wrote...

Dear Alan,

thought that perchlorate was chlorate VII or ClO4-,

not ClO3-

I'm hoping to obtain or manufacture some given the recent results that large amounts are present in the Martian soil analysed by Phoenix.

W.

18th February 2009 16:50

Alan Yates wrote...

Luke,

Platinum wire is expensive, especially for a reasonable gauge that will last in the cell and not have excessive resistance. It is better to buy a commercial Platinum plated anode used for electroplating.

If you happen to have Pt wire hanging around, or lots of cash was waste then by all means go ahead and use it. I was given my wire, so I didn't mind using it. Another option might be buying a Pt coin and beating it into a larger sheet.

Regards,

Alan

18th February 2009 05:08

Luke wrote...

Dear Alan,

I wanted to buy some platinum wire to make an electrolitic cell, so would you suggest me as dimension of the wire to make something good?

thanks

4th May 2008 19:21

Alan Yates wrote...

Tom,

I just crimped the Copper against the Platinum.

I considered soldering it, but never did.

Regards,

Alan

4th May 2008 16:35

Tom wrote...

Hello, I would like to know what solder/weld method you used to join the copper wire in the pasteur pipette to the platinum wire.

Thank you.

25th April 2008 07:36

George wrote...

Dear Alan

Many thanks for your photos , that gave me help to my work , electroplating .

George