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Author: Subject: H2SO4 on an extreme budget?
Radically Dubious

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[*] posted on 10-12-2019 at 05:20

Just came across the following reported reaction at :

S + 3Cl2 + 4H2O = H2SO4 + 6HCl

which is really a confirmation of the hypochlorous acid approach.

I am reporting it as it also suggests a simply process to prepare H2SO4. Just make a suspension of sulfur in water. Pour it into a large vessel filled with chlorine. Shake and let stand. Pour out the treated chlorine water with sulfur, and refill the vessel with chlorine. Add back the previously treated chlorine water with sulfur and shake. Keep repeating the process until the sulfur has vanished.

A few paths to chlorine, like adding NaHSO4 to chlorine bleach (NaOCl).

A more accessible path, but not returning the same proportion of Cl2, start by adding lemon juice, or Ascorbic acid (Vitamin C) to a source of NaOCl, a piece of copper (perhaps a coin, or substitute a piece of carbon), some Aluminum foil (best if preheated in a flame) and finally a large excess of NaCl. The electrochemical reaction results in chlorine. Reference: see

[Edited on 10-12-2019 by AJKOER]
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[*] posted on 10-12-2019 at 05:47

NaOCl added to bleach indeed works quite well. Gives gaseous Cl2 and Na2SO4, which will separate in large crystals as its 10-hydrate.

The other path to Cl2 is totally useless. Adding all those reductors to NaOCl, do you really think that produces Cl2 in significant amounts? Not at all. Ascorbic acid is too weakly acidic and too strongly reducing to give any decent production of Cl2 with NaOCl. There certainly will be a reaction, but not what is needed.


Whether the making of H2SO4 from S, Cl2 and water works in practice should be tried. The reaction in theory can occur, and I also think that in practice it can work. If S is oxidized by Cl2 in the presence of excess of Cl2 and water, then indeed you get H2SO4 and HCl. But from an engineering point of view, I expect this method to be very cumbersome and slow. Cl2 does not dissolve that well in water, powdered S is somewhat hydrophobic and is not easily wetted and it will be hard to get it nicely suspended in water. I think that for making a few ml of H2SO4, you'll need a LOT of time and frequent adding little amounts of Cl2 to the reaction mixture.

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Radically Dubious

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[*] posted on 10-12-2019 at 14:03

From an old thread, which also provides this statement per a cited source:

"3 HOCl + Al --> Al(OH)3 (s) + 3/2 Cl2 (g) Eo net = 3.93 V

This battery cell is theoretically capable of generating 3.93 volts.

Reference: see "

Quote: Originally posted by AJKOER  
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. ...

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.

[EDIT] I repeated the experiment, using an old pre-1982 penny, which is brass, 95% copper, 5% zinc (please see ) 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 ). 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.
[Edited on 5-9-2013 by AJKOER]

And this reported result by Plutonium239:

Quote: Originally posted by Plutonium239  
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.

So, some mixed results (fine-tuning required, like does excess Cl- salt out the Cl2, or consumes it via Cl2 + Cl- = Cl3-). However, some potential with the last comment above being an example of one of the stronger reaction results reported. I suspect the recommendation to place the copper cathode near the top of the solution, as Cl2 is generated at the Cu electrode, may avoid/limit chlorine loss. This is an important point for potential harvesting of Cl2 from HOCl (formed from a weak acid acting on NaOCl) via an electrochemical (battery) cell design without the need for employing a strong acid.

Note, electrochemical reactions characteristically display an inception period, during which there is no obvious reaction. However, in general, I have noticed that, at times, a short microwaving can eliminate/shorten an inception periods. However, in the current experiment, a rapid generation of chlorine while undergoing a short MW treatment, could be problematic and require safety measures. If successful, however, resulting in either timely significant ongoing Cl2 generation or very rapid production, that would be quite interesting.

[Edited on 10-12-2019 by AJKOER]
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