Sciencemadness Discussion Board

Sodium chlorate cells

209 - 16-9-2007 at 09:20

I have just been running my new sodium chlorate cell for about 10 minutes. The cell is a jar sealed jar with a gas outlet (for chlorine and other stuff) Two steel electrodes approx 1 liter of water and 150 grams of salt.

I am running 3-4.5 V @ 600mA. Already a greenish cloud is forming (I am assuming from the dissolved chlorine) and I am not sure if it should be working this fast. should I have a green cloud in under 10 minutes?! And I guess I sodium chlorate should start forming on the bottom of the jar?

thanks!

Bromine - 16-9-2007 at 10:29

green cloud wolud probably be iron (II) compound, chlorine formed reacts with steel electrode. Use graphite or lead electrodes.

hashashan - 16-9-2007 at 14:13

Quote:
Originally posted by 209
And I guess I sodium chlorate should start forming on the bottom of the jar?

thanks!

Sodium chlorate wont be formed at all .. It has enormous solubility.

and the green ... any chance for copper ions?

Anode

MadHatter - 16-9-2007 at 23:17

What are you using for the anode ? If it's copper or copper-plated, the solution will turn green.
Some people using gouging rods use this method to dissolve the copper plating. Personally, I
peel the plating off my rods.

chloric1 - 17-9-2007 at 01:53

See the KCLO3 from water thread. I did get sodium chlorate to crystallize at the bottom of the cell. This is after running 6 amps 14 days then boiling electrolyte to half its volume, and adding more saturated brine and running at the same amps for an additional 7 days with the lid off the last 48 hours to effect evaporation. It was 34 degrees C outside those two days so I lost about 700 ml!:o

hashashan - 17-9-2007 at 03:59

How do you know its the chlorate crystalizes out and not the Chloride?

Xenoid - 17-9-2007 at 04:57

Sigh!...... I guess someone has to say this!

This thread has been running for 24 hours now and I am utterly amazed that Sauron or some other has not recommended that a moderator close this thread and despatch it to Detritus!

@ MadHatter, if you had looked 3 posts above yours, at the initial post, 209 states that he used STEEL electrodes in his chlorate cell. I would be highly surprised if anyone was using their chlorate cell for stripping the copper of gouging rods. I electrolytically strip mine, but in a separate specifically designed tank.

@chloric1, 209 states that his cell has been running for 10 mins at .6A in a sealed jar not 6A for 3 weeks in an open container.

@209, surely after following this forum for a while you would be aware that we don't want yet another chlorate cell thread! Perhaps a moderator could rename the inaptly named "KClO3 from water" thread. Surely you must be aware, even after a modicum of research, that steel cannot be used for a anode in a chlorate cell. Steel will dissolve, that is why there are so many threads on making stable chlorate cell anodes. Graphite or carbon gouging rods are best for a beginner. Even carbon rods from a Zinc - Carbon lantern battery, but NOT steel. As hashashan has (what a mouthfull) pointed out, sodium chlorate is extremely soluble and despite chloric1's experiences to the contrary will almost never crystallise out in a running cell (you are getting confused with POTASSIUM chlorate).

Regards, Xenoid

12AX7 - 17-9-2007 at 08:43

I object. I regularly find deposits of NaClO3 in my cell, when it's been running for a while and the sodium content is high.

Tim

Xenoid - 17-9-2007 at 10:08

Quote:
Originally posted by 12AX7
I object. I regularly find deposits of NaClO3 in my cell, when it's been running for a while and the sodium content is high.

Tim


Hmmmm... I'm not surprised, Tim. I gather you run a large open cell at high currents, the evaporation losses must be huge and I would guess there would be a lot of encrustation around the top of the container at least.

This is hardly the same situation as with 209, sealed cell, .6 Amps for 10 mins.

I run 4.5 litre sealed cells at up to 20 amps (with 10 or 15g per 100ml extra solid NaCl added initially) for over two weeks and I have never reached NaClO3 saturation. Off course, if you keep adding NaCl and losing water to evaporation you will at some point reach saturation, so what! That is hardly the situation in this case!

I did say "almost never crystallise out in a running cell", I'm not sure what you object too!

Regards, Xenoid

[Edited on 17-9-2007 by Xenoid]

12AX7 - 17-9-2007 at 10:17

I object because "almost never" is more like "almost always" in my case. :D But yeah it's understandable: my liquor is already pretty saturated, then there's the added salt, and conversion, and some evaporation (I'm not sure how much evaporation there actually is, but at this rate, there certainly should be a good loss of water to hydrogen and chlorate). FWIW, I would call my cell "closed", as the chlorine smell is noticable in the house if the plastic wadding is loose!

For the "usual" one-off chlorate experimenter, sodium chlorate certainly won't crystallize after the first run, so overall I suppose "almost never" is justified.

Tim

hashashan - 17-9-2007 at 12:35

Once again I don't really understand. Your cell never has 100% chlorate in it ... Id suppose it has about 70%-80% all the rest is NaCl which has much much lower solubility. Why would the NaClO3 crystalize out when the far less soluble NaCl can crystallize out instead?

12AX7 - 17-9-2007 at 15:07

Because NaCl starts at saturation and falls as it is converted to NaClO3, which is already at saturation as well. Due to mutual solubility, there is limited capacity for NaClO3 as the NaCl goes away, but not enough, and it disappears when cooling to room temperature. Likewise, after cooling, I ensure a maximal amount of NaCl by heating the solution and pouring it over rock salt. Some more NaClO3 crystallizes as a result.

Tim

chloric1 - 17-9-2007 at 17:36

I call the first run the "virgin run" because there is little if any isolatable sodium chlorate. The highest chlorate concentrate one can obtain on a virgin run is approx 300 grams per liter based on the intial concentration of the NaCl and the fact you stop when NaCl is at 100 grams per liter to prevent the start of perchlorate which will destroy graphite.

If you boil the virgin run down to 1/2 volume and add saturated brine to restore volume and run again then you get higher chlorate concentration. My Industrial Electrochemistry book states that commercially,(ca 1940) NaClO3 crystallization is performed when a concentration of 750 grams per liter is reached.

209 - 18-9-2007 at 13:46

Thanks for your responces guys! I changed the electrodes and the cell is bubbling away. However my knowledge on electrochem is not that great (Tim :)). You guys talk about how its highly soluable. So then how are you supposed to percipitate it out of the solution?

Xenoid - 18-9-2007 at 14:40

@209 Have you checked out Dann2's website here;

http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

I hope so! Otherwise you are wasting our time!

Basically you need to boil your solution to remove water and bring the NaClO3 level up to saturation, then it's just a matter of letting it cool to say -10 oC. and the excess NaClO3 will crystallize out!

It's all described here;

http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...

Regards, Xenoid

12AX7 - 18-9-2007 at 14:41

Simple, you keep putting in more and more until it can't stands no mores ;)

Near 100g/100ml at room temperature, up to more than twice that at boiling. Large (and more than three times larger than NaCl's), but still finite.

Tim

209 - 18-9-2007 at 18:10

Sounds good. Thanks for your help.....Maybe this is just a damn stupid question, but if you cool the water solution to -20oC then how do you filter it out? Or maybe is it the hypochlorate solution that keeps it from freezing?

Xenoid - 18-9-2007 at 18:43

Yes! It's a damn stupid question!

The high concentrations of NaClO3 and NaCl will depress the freezing point of water!

It's the same reason salt or (salts) are put on roads to stop ice forming!

Regards, Xenoid

[Edited on 18-9-2007 by Xenoid]

209 - 18-9-2007 at 20:35

Well now I have encountered something interesting. Some kind of orange/brown "fluff stuff" has occured at the bottom of the jar. Anyone know what this is, or if this is supposed to happen??!

Xenoid - 18-9-2007 at 21:03

Yes! That will be iron hydroxide, coming from either of your electrodes. If your solution turns a brownish or coca cola colour that will indicate the presence of colloidal iron hydroxide, which is actually quite hard to get rid of, it can't be filtered out.

Just exactly what are you using for anode and cathode now!

Good grief! When will this nightmare end?

Regards, Xenoid

209 - 19-9-2007 at 05:57

I am using short graphite electrodes from batteries. Why should this still be causing a problem!?

Xenoid - 19-9-2007 at 07:11

If you are still using your original solution, the iron(II) chloride from your steel electrodes will get converted to iron(III) hydroxide. If you are using a fresh solution it may just be a bit of battery gunk contamination from your graphite electrodes. In either case I wouldn't worry, it's probably the least of your problems!.....:)
BTW you can use steel or preferably stainless steel for the cathode (-). It's the anode (+) that's most important.

Regards, Xenoid