Sciencemadness Discussion Board

Maximum NaClO % from brine electrolysis

math - 28-12-2011 at 15:54

Hello,

does anyone know what is the maximum/reasonable percentage of sodium hypochlorite produced by a concentrated NaCl (aq.) electrolysis using AA batteries?

What could one expect? How much NaCl is too much or too little to make a strong NaClO solution?


Thank you

hissingnoise - 28-12-2011 at 16:10

You'd need several AA batts. in parallel to produce reasonable yields --- ensure low temperatures to prevent disproportionation to chlorate!
And your electrolyte should be saturated at all times for efficiency's sake . . .
Large graphite gouging-rods make ideal electrodes, BTW!


math - 28-12-2011 at 16:12

Which voltage should I need exactly? Is there any page I can look at for getting ideas?

Also by low temperatures do you mean room temperature (25°C) or lower?
If I saturate water with NaCl at the beginning, do I have to keep adding it as it reacts to form NaClO?

Thank you

DerAlte - 28-12-2011 at 17:23

Your can get up to around 20% if you do it carefully but probably not without a heap of AA batteries! Use a Dc source like a battery charger.

Search this site for hypochlorite. If you try it, keep the temperature of the electrolyte low.

Der Alte

math - 29-12-2011 at 12:53

Thanks for the input. I was looking for something gaugeable in order to use NaClO as a reagent, which would need approximately knowing its concentration to be more than 5-10% found in household bleach.

hissingnoise - 29-12-2011 at 13:06

You could always bubble chlorine into a cold hydroxide solution to get a salt/hypochlorite mixture.


Adas - 29-12-2011 at 13:23

Quote: Originally posted by hissingnoise  
You could always bubble chlorine into a cold hydroxide solution to get a salt/hypochlorite mixture.




But messing with so large amounts of chlorine is not good. Especially not for an amateur chemist.

hissingnoise - 30-12-2011 at 02:43

Starting on the very small-scale should be innocuous enough?


math - 1-1-2012 at 06:19

Thanks for your reply.

I'm interested in the electrolysis process though, as it seems less messy.
Also if I'd go for chlorine production, I'd get it only from bleach and HCl, which given what I'd like to achieve, seems pretty pointless.

Is there any particular voltage, NaCl concentration or anything else which could tell me roughly
which percentage of NaClO is there after stopping electrolysis?

Or should I go as (example) performing electrolysis of a saturated NaCl solution at 10°C at 9 volts for 1 hour, then measure the density and refer to an aqueous sodium hypochlorite specific gravity chart to know how much NaClO is there?

Thank you

hissingnoise - 1-1-2012 at 07:12

Quote:
I'm interested in the electrolysis process though, as it seems less messy.

It ain't nececelery so!
You can use manganese dioxide, potassium permanganate or even, if you've nothing else, lead dioxide, to oxidise HCl!
The process can actually be more quantifiable than anodic oxidation of NaCl.
The product, though, will be an equilibrium mixture of NaCl and NaClO!


UnintentionalChaos - 1-1-2012 at 07:59

Quote: Originally posted by hissingnoise  
Quote:
I'm interested in the electrolysis process though, as it seems less messy.

It ain't nececelery so!
You can use manganese dioxide, potassium permanganate or even, if you've nothing else, lead dioxide, to oxidise HCl!
The process can actually be more quantifiable than anodic oxidation of NaCl.
The product, though, will be an equilibrium mixture of NaCl and NaClO!




There's a lovely thread on chlorine generation by len in prepublication. TCCA is the best choice for chlorine generation and has worked smoothly for me when making high strength hypochlorite solutions before.

hissingnoise - 1-1-2012 at 08:22

Yeahhh, but chlorine is one of my least favourite smells ─ don't like bleach either . . .


hissingnoise - 1-1-2012 at 08:37

Probably the definitive thread!