Sciencemadness Discussion Board


blindreeper - 18-3-2003 at 23:56

I am going to start getting into making chlorates (NaClO3) for rack-a-rock type things.

Well I tried it last night in a big nescaffe coffee jar. I had 2 carbon elecrodes in a very saturated salt solution. I left it for 2 hours came back and wow it was all black!!! The electrode got attacted somthing fierce.
The problem I think was that the voltage was to high. I had a battery charger (car) it was on the 12v section (it can switch from 6v to 12v) and the heavy duty charge (it also has trickle charge).

I will try with a steel cathode and a carbon anode with 6v and trickle charge. Any help on what I can do and what a good material for electrodes would be would be much appresitated.
BTW, the cell was sealed with a 3mm vent hole in it (if that makes a difference)

I have read a bit on the subject and found it quite interesting. Also the electrodes in a car battery are Pb arn't they? Are they good for chlorate production?(i have no intentions of making perchlorates)

Cappy - 6-4-2003 at 18:54

Half of the electrodes in a car battery are lead. The other half are lead oxide.

Battery Chargers

MnkyBoy - 11-4-2003 at 07:01

If using a car battery charger, dont do so directly. Connect the charger to a battery that it was intended for. Connect the battery to your cell. By doing this, the charger's output wont fluxuate as bad.

Just a hint read some place.

markx - 7-8-2003 at 03:00

For cathode one could use stainless steel (done so and it holds up great!)or regular mild steel (corrodes pretty fast) anode can be made out of graphite or lead (IV) oxide PbO2.
Platinum and rare earth oxide mixtures are also possible but I don't think one can get ahold of these. So the only options are graphite and lead oxide....
The latter can be prepared by electrolysis of lead nitrate but messing with lead compounds has a rather questionable nutritional value so graphite is the sane choice.
Graphite rods from batteries are bad for chlorate production since they don't hold up much. I used a piece of industrial graphite anode and this sucker seems to last forever compared to the battery sticks.
There's no profit in messing with a few 100 ml cell, take a healthy several litre cell and a meaty rectifier (20-50A @ 12V ) bang 15-20A DC through your setup overnight and you'll see some results!
I messed around with small cells and short reaction times in the beginning myself and got rather desperate since it just would not work....
It was when I upgraded to a meaty cell and power supply that I started getting a hang of this method.
There is no need to stabilize the DC ripple of the battery charger it works great on unfiltered DC straight out of the bridge.

hissingnoise - 22-8-2003 at 11:59

Oxidizing nacl takes patience; it takes forever to saturate the sol because naclo3 is so soluble.
It can be precipitated by kcl as kclo3, but if you want naclo3(more powerful oxidizer when dry)carry on the electrolysis for aeons.

chemoleo - 22-8-2003 at 16:09

... there are a number of other threads on making chlorate... read them!! there is lots of useful info on different electrode materials. the graphite problem is well known... but otherwise it still works! have u tested the chlorate yet??

theh0ser - 6-12-2003 at 23:32

why is it that when i use to pencils (graphite) as electrodes and a solution of salt and water and electrolize it, after a few minutes, thers a strong smell of chlorine?

chemoleo - 6-12-2003 at 23:44

lol, are you serious?
Ok read other threads first :)
Then... pencil graphite doesnt work, tried it myself with various grades. It corrodes, and is not very strong, i.e. it splits into splinters.
YOU WANT THE SMELL of chlorine by the way!!
The point is to keep it in a closed container, so as to make sure that the free smelly chlorine reacts with the NaOH, to form NaOCl and Nacl (the latter being electrolysed again).
So... the smell is what you want, except that you shouldnt smell it as it should be in a container that allows it to react with the mixture!! There are plenty of threads on this! read them!

theh0ser - 7-12-2003 at 00:05

aright calm down there chameleo...i dont spend hours reading every single thread

vulture - 7-12-2003 at 14:25


YOU SHOULD spent hours reading every thread about the subject! This is not a Help-me-cause-i'm-lazy-chatroom! :mad:

If you can't be bothered by reading those threads, we can't be bothered to help you. Nor will you ever succeed in anything.

Anyways, your posting style is really annoying. Consider this as a warning.

[Edited on 7-12-2003 by vulture]

theh0ser - 7-12-2003 at 22:44

well i read all the threads in this topic but it still didnt answer my question

Quantum - 11-2-2004 at 21:57


What questions? All you asked about was the Cl smell and Vulture told you about that. The best I understand it(still learning) is that because you start with salt(NaCl) and water in a solution and then run the current through it you are breaking the Cl from the Na and the H from the O so the Na joins up with the OH forming NaOH.

NaCl + H2O --> NaOH + Cl + H? Not balanced!

I guess one mole of H would be unused along with the Cl and go away into the air. I don't understand the NaClO3 reaction very well so if someone could explain in I would be greatfull. I am thinking you need 3H20 for every NaClO3 you make and lots of pure H gas is given off?

NaCl + 3H2O --> NaClO3 + H2? Balanced I think

Anyone who knows what they are doing care to point me in the right direction?


axehandle - 11-2-2004 at 23:04

Use stainless steel for the cathode, and a pure platinum wire as the anode.

I know it sounds expensive, but I've just ordered a 300mm long wire, 0.7mm thick and it only cost me about $90.

Considering that it will last forever, I think it's a good investment.

Current Density, not Voltage

Turel - 12-2-2004 at 08:26

The problem I think was that the voltage was to high.

Your problem is that your electrodes are too small/your current density is too high. Voltage has nothing to do with electrode decay. It either decays, or does not. The rate of decay is proportional to the current density.

Your problem is likely not even due to ion-induced decay. Graphites layered planar sheet structure makes it a piss poor choice for even medium current densities, as the bonds between sheets are very easily broken.

Carbon graphite is fairly inert, and I doubt the chloride ions are to blame. Use longer electrodes to lower the current density on the graphite.


Cheap electrodes

Turel - 12-2-2004 at 09:12

I have successfully electrolyzed brined using stainless steel electrodes. Stainless steel silverware is cheap and dense. SS handles higher current densities very well, which are recommended for the oxidation of chloride.

Commercial production of hypochlorites use a SS coil cathode surrounding a central perforated cylindrical iridium anode, and use strong current densities on the anode to favor oxidation of the cloride ion to Cl+. The reaction chamber is kept as cold as possible to inhibit thermal decomposition of the hypochlorites to chlorates.

Quantum: The electrochemical reaction proceeds as thus:

Anode Reactions: Cl- -2e ---> Cl+
Cl+ + H2O ---> ClO- + 2H+

Cathode Reactions: 2Na+ +2e ---> 2Na
2Na + 2H2O ---> 2Na+ + 2OH- +H2

The 2H+ and 2OH- produced obviously eliminate to retain a neutral pH.


[Edited on 12-2-2004 by Turel]

axehandle - 12-2-2004 at 09:29

Iridium? Sounds too complicated, I'll stick with my platinum.


Turel - 12-2-2004 at 09:32

They cost the same, and iridium is pretty much guaranteed to last far longer than you or I. Platinum will corrode over time, and needs to be cleaned.

Cleaning an iridium electrode is as simple as wiping it off.

axehandle - 12-2-2004 at 09:33

Hmmm. Bad purchase, then..... sigh.

Not True

Turel - 12-2-2004 at 09:37

Pt electrodes will do anything you could want to do with them. I am just saying that commercial applications often prefer iridium due to a high usage demand.

Ir electrodes are the best IMO, but are by no means a necessity. I don't even own a set of Pt electrodes, and I can get anything I need done just using SS and carbon. So Pt is still a great thing to have on hand.

axehandle - 12-2-2004 at 09:41

That's a great relief then. The platinum wire I've ordered will btw be used for KClO4 production as well as production of a small quantity of Pt-on-silica algae substrate catalyst (for making concentrated sulfuric acid). The latter should only require about 100mg worth, though.

vulture - 12-2-2004 at 13:46

Why did you buy wire? The surface area is rather small.

Pt coated Ti anodes have a far greater surface area, last as long and are cheaper.

Ofcourse, you could always dissolve your Pt and precipitate it onto a Ti matrix.

EDIT: I merged Turels reply with the thread, but it's a few replies higher now.

[Edited on 12-2-2004 by vulture]

axehandle - 13-2-2004 at 02:14

Because there's no fscking way in hell a company here would sell platinized Ti net to an individual. I'd have to burglar my way in and steal some, if I wanted it that badly.

(Hmm, perhaps not such a bad idea. I certainly am more qualified than your average thief when it comes to disabling alarm systems....hmmmm..... no. Too risky.)

Also, I need a small piece of pure Pt for dissolving in aqua regia and precipitating it on silica algae or rockwool, then burning off the chlorine, thereby platinizing the substrate, for H2SO4 synthesis.

The electroconductivity of Pt is rather low, on par with Fe. I hope the wire won't melt....

And the surface area can be increased by hammering the wire flat. It's not like I'm planning to produce more than perhaps 100g of KClO4/week, anyway. I just need small amounts as an additive to my rocket fuel. You _can_ buy it here, legally, but it's expensive and anyways it's more fun attempting to make it yourself =).

You build rockets, too?

Turel - 13-2-2004 at 11:54

Shit, man. I didn't know you were into rockets. We may have quite a few projects in common. Strange.

axehandle - 13-2-2004 at 12:13

I'm very much into rockets. Check your U2U inbox, mate....