Aunvre - 5-1-2013 at 21:55
Alright, so this whole debacle started when I wanted to accomplish the relatively simple task of synthesizing sodium chlorate from a brine solution.
To my knowledge, it was successful, and I have a small amount of grayish-white colored powder (I used graphite for both the cathode and the anode,
whatever). However, when I decided to take it a step further and make sodium perchlorate, all the recipes I've found call for the exact same procedure
as making sodium chlorate, which is the electrolysis of brine. Same with sodium hydroxide.
Now, I understand the basic chemistry behind the electrolysis, but I am still definitely regard myself as an amateur chemist. I sort of understand how
the sodium perchlorate works (when the chlorine-emitting node stops releasing gas), but I'm unsure about a stopping point, and the lye thing
completely escapes me.
1 - Tube for disposal of gas, allows for indoor use
2 - Brine
3 - Cathode \
+-- Both graphite
4 - Anode /
This is my setup for electrolysis of brine. A 12 volt, 1 amp power supply was used. Is this an appropriate setup for making NaClO3/4 or sodium
hydroxide? If not, what's wrong with it?
TL;DR - What exactly is the process for making sodium (per)chlorate and hydroxide, and what specifically distinguishes the two processes?
(and is my electrolysis setup appropriate?)
elementcollector1 - 5-1-2013 at 22:01
Sodium perchlorate: Electrolyse sodium chlorate with a stronger anode. PbO2, MMO-mesh, or platinum electrodes are supposed to work (not sure on MMO).
Sodium hydroxide: Separate the electrodes by placing two beakers side by side, one being full of saturated salt solution and the other distilled
water, with a piece of tissue paper or paper towel wetted with the salt solution connecting the two. Alternatively, one flowerpot inside of another
can be used. Place the cathode (-) in the distilled water and the anode (+) in the salt solution, and charge it with a very high current (not house
current, but a car battery charger will do). Collect from the distilled water (now lye water) solution, and boil in a steel container (not glass, as
the NaOH could come out molten, eating through the glass in a heartbeat).
The reason you have to split the electrolysis cell up is that any NaOH produced in a single cell would immediately react with the dissolved Cl2 from
the anode to form NaOCl (bleach), and eventually NaClO3, NaClO4, etc.
That clear things up? 
AndersHoveland - 5-1-2013 at 22:08
The process for making sodium hydroxide generally tends to be set up to allow the chlorine gas to escape, and the industrial process uses a
semipermeable membrane (which allows sodium ions to pass through, but not hydroxide ions) to prevent the sodium hydroxide from reacting with the
chlorine being produced at the anode.
The process for making sodium chlorate uses a warm solution, to encourage the hypochlorite to disproportionate into chlorate.
The process for making sodium perchlorate typically involves higher currents, and the use of special electrodes becomes much more important. While
perchlorate can be made from brine in a single step, the process is more efficient if chlorate is made first, separated out from the chloride, and
then electrolysed again. The reaction dynamics are different in this process, since the chlorate is being oxidized by hydroxyl radicals being
transiently produced at the anode (or in some instances, depending on the anode, by the metal oxide coating).
[Edited on 6-1-2013 by AndersHoveland]
Aunvre - 6-1-2013 at 12:19
Thank you Anders and element, both of those explanations helped immensely.
Traveller - 26-1-2013 at 00:43
In this type of cell, spacing of the electrodes is important to avoid the escapement of chlorine gas. It actually makes chlorine gas at the anode and
sodium hydroxide at the cathode, but only briefly. What is made almost instantly becomes sodium hypochlorite and hydrogen.
Under 50° C., it will produce sodium hypochlorite. Between 50° and 70° C., it will produce sodium chlorate. From what I have read, making
perchlorate requires more exotic materials for electrodes, as someone pointed out, but I thought I also read that it required lower current PLUS lower
temperatures.