I bought a 3 ft plastic tube in order to collect chlorine gas in a second bottle. When doing electrolysis, I used aluminum foil as the anode and iron
as the cathode.
Thirty minutes after the setup I noticed a white precipitate forming around the iron electrode while the aluminum foil was still reacting without the
iron making contact with the water. What could that white precipitate be and why was the aluminum foil still reacting without current, probably some
NaOH?
Clonejeffie - 25-2-2017 at 21:24
Maybe NaCl? elementcollector1 - 25-2-2017 at 22:04
Either that or Al(OH)3. AJKOER - 26-2-2017 at 05:24
NaOH attacks aluminum. Iron readily reacts with HOCl.
As such, the Al (or carbon) electrode should be used to produce Cl2 (and with water, HCl and HOCl) and the Fe (or other material preferably inert)
electrode the NaOH.
Use a divided cell (so that the Cl2 and NaOH cannot react to form chlorine bleach, NaOCl and NaCl) connected by a salt bridge.
---------------------------------------------
My suggestion on a better path to hypochlorous acid is by the action of a dilute mineral (like diluted H2SO4 or even dilute aqueous NaHSO4) or even
CO2 gas (from vinegar and baking soda) acting on a hypochlorite resulting in HOCl. For example, add CaCl2 to chlorine bleach (NaOCl) and then shake in
an atmosphere of CO2. Decant the HOCl contaminated with NaCl, but can be distilled (just half way, liberating nearly all the HOCl and Cl2O) to acquire
pure and almost twice as strong HOCl (see reference at https://www.sciencemadness.org/whisper/viewthread.php?tid=71... ). Use quickly or cold store out of light. Do not place in a jar with a metal cap
plated with a transition metal (like tin).
How do I overcome the resistance produced by the salt bridge. Would a paper membrane sandwiched between cardboard work?
My recollection is that more modern patents describe porous ceramic based membranes (see, for example, https://www.google.com/patents/US5628888 ). The latter are non-reactive with respect to HOCl/Cl2, unlike paper/cardboard.
Unfortunately, such technologies are beyond my expertise in this area.
