[hotwheelharry]

I have a setup with NaCl saturated H2O solution. I have graphite electrodes. I performed electrolysis on the solution and got chlorine gas, hydrogen gas, sodium hypochlorite (the water smelt like bleach), and some strange brown precipitate. I was wondering what the brown precipitate was.

Thanks.

[cliverlong]

(a Guess)
Maybe the electrodes have shed some graphite.
If you isolate the "precipitate", wash it and place a voltage across it does it conduct electricity?

I would guess the graphite does not react with the hypochlorite solution

[hotwheelharry]

If the graphite got into the water, why is the precipitate brown. The electrodes are jet black. Also there is a significant amount of this stuff produced that floats to the top. It's not bubbles though.

[aeacfm]

Graphite is not corroded  i think the voltage used was sufficient to ppt other metal compounds and combine together to form the brown form

[cliverlong]

If the graphite got into the water, why is the precipitate brown. The electrodes are jet black. Also there is a significant amount of this stuff produced that floats to the top. It's not bubbles though.

It is a guess
Note that the same material in different forms can look completely different
(Maybe not the best example) http://www.georgiagulfsulfur.com/properties.htm
It may be possible that the electrodes of compressed graphite are shiny and small particles shed are dull brown
Is it possible that small gas bubbles generated by the experiment are sufficient to lift the particles to the top of the liquid?

Maybe the brine was impure and other compounds or ions were present ?

[aeacfm]

Chemical reactions occurring in brine processing:

[10]  CaSO4 + Na2CO3 ==> CaCO3 +NaSO4  (CaCO3 precipitates) 
[11]  MgCl2 + 2NaOH ==> Mg(OH)2 + 2NaCl  (Mg(OH)2 precipitates) 

http://electrochem.cwru.edu/encycl/art-b01-brine.htm

[hotwheelharry]

@cliverlong: sorry, I didn't mean for my reply to sound argumentative. I was simply offering evidence to the contrary. Nice article by the way.

I can't think of why there would be any brown precipitate in there other than the fact that maybe the solution was impure. I did use sea salt, so maybe there was something in there... from the sea ;p. Yep, i'm going to say it was impurities.

The only other thing I thought could have happened was that somehow Carbon was involved in a chemical process and that created a Carbon based precipitate.

[cliverlong]

@cliverlong: sorry, I didn't mean for my reply to sound argumentative. I was simply offering evidence to the contrary. Nice article by the way.

No offence taken

I can't think of why there would be any brown precipitate in there other than the fact that maybe the solution was impure. I did use sea salt, so maybe there was something in there... from the sea ;p. Yep, i'm going to say it was impurities.

Sounds plausible to me.

I suppose further tests would have to be done on the "precipitate". What might be useful? Flame tests to see if colours indicate presence of particular metal ions.? Anion tests? Solubility in acids / alkali?