I have been messing with electrochemistry lately, and had saturated some water with NaCl (table salt). I then placed two carbon electrodes into the solution and ran a current through it. To my surprise, the carbon dissolved and a dark brown powder formed in the solution, with gas bubbles rising from both electrodes until they were gone. Anybody know what is happening??

orksecurity7 years ago
H20 -> H2 + O2, presumably. And erosion of your electrodes.
Metalyc6 years ago
The currant (when I posted this) top answer is wrong. Magnesium electrodes would make Hydrogen and oxygen gases, but you were using a Carbon electrode. That separate the Chlorine and Sodium, the sodium then reacts with the water, which I guess is the brown discolouration.

NOT H2O -> H2 + O2
IS NaCl -> Na + Cl2
(Na + H2O -> NaOH + H2) [NaOH is lye, a base]
CAUTION Chlorine gas is VERY dangerous!
Dr.Bill7 years ago
Use Stainless Steel  for the electrodes.
Dr.Bill7 years ago
Don't use table salt. Use instead 1 Tablespoon baking soda to 1 gallon of water. Use reverse osmoses water found out of the machine in wal-mart it is more pure than distilled and lasts longer without the browning problem.
Know that 1 electrode will go a dull grey due to plating. Use a lower amperage too. High amps will burn the water. All electrodes have to be of the same metal composition. Keep the electric connections dry by placeing them outside the water chamber. Seal all through chamber holes with silicon RTV.

Electrolysis is actually a form of electroplating. If you use .999 Fine silver bar on the electrode that goes grey, it will plate off to the other electrode and you will have a silver plated electrode. I think the one that goes grey is the Negitive side, So the Positive side will be the silver plated electrode.

Low amperage is the key or the use of a Pulse Width Modulator is called for. Find the PWM through Google Search. They are costly but worth it.