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Old Jul 3rd 2016, 06:27 PM   #1
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Question Electrolysis Of Saline Solution Yielded Unexpected Percipitate

I have recently conducted an experiment aimed at producing sodium hydroxide (NaOH) from a saline solution using an electrolysis method. I did this outside so as to disperse the various gases of H2 gas and Cl2 gas but I also made sure no outside contaminants, such as dirt, were introduced into the experiment. My question is: Why did the electrolysis of a saline (NaCl(aq)) solution using stainless steel electrodes at 18V turn the solution brown and create a precipitate as well as turning one of the electrodes a copper sheen and color? Also; What are the leftover products and what should I do with them?

I began by pouring 500 ml of distilled water into a 500 ml beaker at room temperature
Then I added 16 g of pure, non-iodized table salt (NaCl) and stirred with a glass stirring rod
After seeing that the solution was not fully saturated I slowly added more salt and stirred, repeating this process until I was able to see a tiny amount of undissolved salt at the bottom of the beaker
Then I securely attached my two electrodes to the side of the beaker (originally part of a broken antennae), which I thought were stainless steel, with two plastic bag clips and I made certain the electrodes were not in contact
I then proceeded to attach the dry ends of the electrodes with alligator clips to a handheld drill battery with a voltage of 18V
Immediately a large amount of bubbles (I assume mostly H2 and Cl2 gas) started forming, as expected, however a black froth (I expectt forming from an impurity) was created and about 25-30 minutes later began disappearing
I allowed this experiment to proceed for approximately another 2.5 hours the amount of bubbles steadily decreased and the solution turned gradually more orangeish-brown (as opposed to its initial clear/white color of a saline solution) in addition a blueish-green foam formed on top of the liquid and persisted until the voltage was removed, at which point it slowly dissipated. In addition, I noticed an odd precipitate begin forming near the end of the reaction (I possibly could have missed it before).
Finally I poured the final brownish solution off into a 500 ml Erlenmeyer flask (although some precipitate was also carried over) and left the majority of the precipitate in the beaker I used for the Electrolysis. Also the electrodes which I thought were some type of stainless steel, appear to have been altered in the reaction. The anode, negative electrode, gained a dark coating, which I partially removed on one side with a scrub brush, to reveal a copperish gleam and color were it was in solution, whereas the cathode, positive electrode, remained relatively the same with some dark coating/smudging that is somewhat removable.
I have photographed all materials used in the experiment as shown here: http://imgur.com/a/X0GgS
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