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blogfast25
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Quote: Originally posted by Cou  | | I don't think that would work because chlorine is so soluble in water, [Edited on 1-9-2013 by Cou] |
Solubility in water isn't that great: acc. Wiki in STP about 1.125 L of Cl2 per 1 L of water. That's about 0.05 mole/L. Once the
solution is saturated with chlorine, any 'excess' chlorine will of course escape.
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AJKOER
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I agree that this is not a classic quick (forceful) chlorine generation tool. It may, however, be a gradual long lasting method for some
applications. Note, there is quickly an evident chlorine smell, so perform this experiment in a sealed chamber or outdoors.
Some Chlorine probably reacts with water as follows:
Cl2 + H2O <-----> HCl + HOCl
, which is not completely a bad thing as more hypochlorous acid will fuel the battery and eventually form more Cl2 and Al(OH)3. In addition, the
following reaction could move the above reaction to the right:
3 HCl + Al(OH)3 ---> AlCl3 + 3 H2O
, but to a lesser extent if the copper anode is not in contact with the jelly like clear Aluminum hydroxide (which resides at the bottom of the
battery cell).
Heating the solution should help drive off any unreacted chlorine.
Bottomline, not a great path to rapid, or possibly abundant chlorine generation (due to secondary reactions), but does have interesting side
products.
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[EDIT] I repeated the experiment, using an old pre-1982 penny, which is brass, 95% copper, 5% zinc (please see
http://en.wikipedia.org/wiki/Penny_(United_States_coin) ) and added no NaCl to the solution this time (the Cu/Zn alloy is apparently more reactive
than pure Cu). I also moved the copper anode to be near the top of the battery cell.
Now, Chlorine is formed at the copper cathode with hopefully reduced solution contact by the reaction :
3 HOCl + 3 H3O+ + 3 e- ⇒ 3/2 Cl2(g) + 3 H2O
and today I noticed more solids suspended in the solute with a tint of green. I suspect the formation of some copper hydroxychloride, Cu(OH)2.CuCl,
which exists as a greenish insoluble solid in near neutral solutions (see http://en.wikipedia.org/wiki/Copper_oxychloride ). I also observed possibly more Chlorine generation as there was as an obvious gas buildup. Now,
this is most likely not entirely H2 given the rapidity of its creation and the avoidance of employing any excess Aluminum (the Al was completely
dissolved in the first few hours).
I wish to thank Cou for his comment as the source of the inspiration to move the copper cathode to a higher position in the battery cell. It appears
to have increased Cl2 output and created a more visible alternate oxychloride.
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My speculation, on the formation of the Copper oxychloride.
Cu + 2 OH- ---> Cu(OH)2
Cl2 + H2O = HCl + HOCl
Cu(OH)2 + 2 HCl = CuCl2 + 2 H2O
Then, per Wikipedia, equation (3), for example, at http://en.wikipedia.org/wiki/Copper_oxychloride
2CuCl2 + 3 OH- → Cu2(OH)3Cl + 3 Cl-
Interestingly, the formation of Cu(OH)2.CuCl may limit the creation of the insoluble Al(OH)3. In addition, the reaction of any formed Aluminum
hydroxide with the chloride ion could form an Aluminum oxychloride.
[Edited on 5-9-2013 by AJKOER]
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Plutonium239
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I just did this last night. So much chlorine was produced that the stopper on my flask was blown off, but it all turned out well. Now I have a
really cool sample of chlorine.
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AJKOER
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Plutonium239:
I hope that you did not employ an excess of Acetic acid relative to the Bleach in the formation of the Hypochlorous acid for the Bleach battery cell.
My concerns reside with a potential formation of Chloroacetic acid, ClCH2CO2H, in the Bleach cell with excess Acetic acid undergoing chlorination.
While this acid is usually created in the presence of Acetic anhydride, I would not rule out its formation entirely.
To quote Wikipedia (http://en.wikipedia.org/wiki/Chloroacetic_acid ):
"The predominant method involves chlorination of acetic acid:
CH3CO2H + Cl2 → ClCH2CO2H + HCl
Acetic anhydride serves as a catalyst for this reaction."
As Chloroacetic acid is toxic, an alkylating agent (see http://en.wikipedia.org/wiki/Alkylating_agent#Alkylating_age... ) and a strong acid (pKa 2.85), I would strongly advise employing a stoichiometric
excess of Bleach relative to vinegar to avoid its possible creation upon chlorination. One could also prepare HOCl by the action of an alternate weak
acid (Ascorbic, Boric, ....) on NaOCl.
[Edited on 6-9-2013 by AJKOER]
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