Specialty Chemistry Forums > Citizen Chemist
Electrolysis of NaCl solution
horsebox:
--- Quote from: Grundalizer on October 31, 2010, 05:02:55 PM ---No matter how hard you try, you cannot get chlorine gas from the electrolysis of aqueous sodium chloride (NaCl). You will get Hydrogen and Oxygen gas.
If you want O2 gas it's much easier to just take apart an alkaline battery and extract the black manganese dioxide, then add store bought hydrogen peroxide. Oxygen gas will bubble out which you can then use to make things burn more brightly, which is pretty cool.
--- End quote ---
When I did this I could clearly smell Cl2. It was a decent sized lab and the whole place stank of chlorine after a few minutes of people experimenting with electrolytic cells so I assume a significant quantity of the stuff can be formed this way. No idea how it could be collected though.
As for H2O2 and MnO2, I'm gonna try this out since I have a fair bit of MnO2 lying around.
Catsceo:
Would't this form hypochlorites, chlorites, chlorates, and perchlorates? Wikipedia says unless you use a membrane cell, you won't get, or at least won't get much, chlorine. I intended to use this method to get ahold of chlorates and perchlorates. Would this not work for what I was planning?
Grundalizer:
It would still be 100x times cheaper and easier to just buy perchlorates in their salt form rather than even attempting to make them from NaCl electrolysis. I've done that electrolysis 1000 times and never once smelted chlorine. Perhaps it's like Hydrogen Sulfide in that we can detect parts per billion, because it is made in such small quantities it's not even worth trying to collect by that method.
bromidewind:
You won't get (much) Cl2 out of a simple salt-water solution because it's at a constant concentration, i.e. everything's jumbled together. The membrane cell Catsceo mentioned separates the Na+ and Cl- ions via a membrane, allowing Cl2 to be collected at the anode and oxygen at the cathode, with NaOH as a byproduct.
You can see a nice Flash animation of the membrane cell at work over here.
Catsceo:
--- Quote from: Grundalizer on November 13, 2010, 10:11:04 PM ---It would still be 100x times cheaper and easier to just buy perchlorates in their salt form rather than even attempting to make them from NaCl electrolysis. I've done that electrolysis 1000 times and never once smelted chlorine. Perhaps it's like Hydrogen Sulfide in that we can detect parts per billion, because it is made in such small quantities it's not even worth trying to collect by that method.
--- End quote ---
I tried a carbon anode and got a big wiff of chlorine. Perhaps I need a better one that won't release too much of it. Also, I'm trying to do a demonstration by making a solution of sodium per/chlorate and adding KCl to precipitate out potassium per/chlorate.
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