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Author: Subject: Catalytic oxidation of sulfurous acid
weiming1998
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[*] posted on 17-1-2012 at 16:06


Quote: Originally posted by Endimion17  
Maybe you should check your premise first. There's no such thing as sulphurous acid being made by blowing sulphur(IV) oxide in water. The H<sub>2</sub>SO<sub>3</sub> molecule doesn't exist in water.

Burning sulphur and stuffing the produced fumes in the water produces a solution of SO<sub>2</sub> and sulphuric acid (from traces of SO<sub>3</sub> made by the reaction of hot SO<sub>2</sub> with atmospheric oxygen).
Bubbling sulphur(IV) oxide through water doesn't produce sulphurous acid.


Technically it is not H2SO3, but it is more convenient to call it that instead of "an aqueous solution of SO2" or "SO2(aq)"
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[*] posted on 17-1-2012 at 21:56


Interesting point on H2SO3.

But, as a matter of chemistry, HOCl reputedly will oxidize S, SO2(aq) or H2S(aq) to H2SO4 (See Watt's Dictionary of Chemistry, Vol 2, page 16).

The solution, certainly at first, is most likely dilute H2SO4.

Note, any free Cl2 will react with any CaCO3 suspension (from H2CO3 + Ca(OCl)2 ) that was not completely removed upon filtering as follows:

CaCO3 (Suspended in water) + H2O + 2 Cl2 --> CaCl2 (aq) + CO2 + 2 HOCl (aq)

This reaction is also referenced in Watt's (page 12).
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weiming1998
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[*] posted on 17-1-2012 at 23:28


Quote: Originally posted by AJKOER  
Interesting point on H2SO3.

But, as a matter of chemistry, HOCl reputedly will oxidize S, SO2(aq) or H2S(aq) to H2SO4 (See Watt's Dictionary of Chemistry, Vol 2, page 16).

The solution, certainly at first, is most likely dilute H2SO4.

Note, any free Cl2 will react with any CaCO3 suspension (from H2CO3 + Ca(OCl)2 ) that was not completely removed upon filtering as follows:

CaCO3 (Suspended in water) + H2O + 2 Cl2 --> CaCl2 (aq) + CO2 + 2 HOCl (aq)

This reaction is also referenced in Watt's (page 12).


That way of making HClO is very interesting, I will try it some time.
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[*] posted on 17-1-2012 at 23:38


So I repeated my experiment yesterday with unflavoured soda water today. This time, 100mls of soda water is poured into a flask. Again calcium hypochlorite is added. This time
chlorine evolution is very low/non existent. A very fine mist of CaCO3 is suspended in the solution. I filtered it but only managed to filter off some of the mist. The solution is added to the leftover sulfur from yesterday. I waited for about 5-6 hours before pouring the solution out, now which appears to be clear, probably because calcium carbonate is insoluble in water, but calcium sulfate is slightly soluble. The solution is heated to about 25mls. This time, when added to dry sodium carbonate, the sodium carbonate turned green, but there was minimal fizzing! What's more strange is that when sodium carbonate solution is added to the acid, instead of fizzing, a white precipate forms! Is the precipate sodium sulfate? or something else entirely? The precipate formed on contact with the acid solution.

[Edited on 18-1-2012 by weiming1998]
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[*] posted on 19-1-2012 at 06:15


OK, starting with Bleaching powder, Ca(OCl)2/CaCl2.nH2O/Ca(OH)2, and added H2CO3. Products are:

Ca(OCl)2 + H2CO3 --> CaCO3 (s) + 2 HOCl

Ca(OH)2 + H2CO3 --> CaCO3 (s) + 2 H2O

Also, assuming a limited partial hydrolysis of the CaCl2 hydrate:

CaCl2 + 2 H2O <----> Ca(OH)2 (s) + 2 HCl

and the created Ca(OH)2 reacting with CO2 to form more CaCO3. Also, a corresponding small amount of Chlorine from any CaCl2 hydrolysis:

HCl + HOCl <---> H2O + Cl2

I would try and separate out the CaCO3 suspension (by adding some H2O and shaking and waiting till it settles), and not filter, as the organic filter paper may be bleached and consume some of the HOCl. As there is still some CaCl2 free in solution with any formed H2SO4:

CaCl2 + H2SO4 --> CaSO4 (s) + 2 HCl

so this is a visible check on the ability of the solution to produce a sulfate (including H2SO4), but as long as there is free Ca ion (from the CaCl2), only or mostly CaSO4 will be created. Hence, the need to remove the CaCl2 (free Calcium ion), which could be done via distillation.

Also, again some Chlorine formation:

HCl + HOCl <---> H2O + Cl2


[Edited on 19-1-2012 by AJKOER]
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weiming1998
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[*] posted on 19-1-2012 at 16:57


I just tried bubbling ozone/air through sulfurous acid, then boiled it down from 500mls to 70mls. It increased my yield, but I don't know the concentration. It was already slightly fuming, but maybe that's water vapour. It didn't work when I tried to ignite potassium chlorate/sugar. By this stage, it can already attack iron quite vigorously, much like aluminum in HCl, when heated.

Also the heat coming from the beaker was much hotter than normal water vapour. It was already very hard for me to put my hand near the opening of the beaker, as the full heat blasted with enough force to scorch skin. Since I don't have a thermometer, I can't tell the exact heat. I might go buy a thermometer.

[Edited on 20-1-2012 by weiming1998]
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[*] posted on 19-1-2012 at 19:14


I don't understand why we are using oxidizing agents here, wouldn't electro-oxidation be cleaner and cheaper?




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[*] posted on 19-1-2012 at 22:15


Quote: Originally posted by Sedit  
I don't understand why we are using oxidizing agents here, wouldn't electro-oxidation be cleaner and cheaper?


As I said before, I don't have a power switch that can do electrolysis without short-circuiting the whole house. Lantern batteries can only do a day or so of electrolysis, and is only 6 volts.
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[*] posted on 20-1-2012 at 00:26


Dude any adapter that plugs into the wall could be used for such a simple synthesis. You can by these adapters for 12 volts and over 1Amp with ease and they are dirt cheep. Yes I would recommend a resistor in the line to prevent it from over heating but for the most part there should be almost no issues what so ever.




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[*] posted on 20-1-2012 at 00:45


How much do they cost and where do I buy those adaptors? They are certainly very useful for electrolysis.
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[*] posted on 20-1-2012 at 00:57


They are on your cell phones your old nintendos (over 1 amp) and almost anything that plugs into the wall. They are nothing special they are just a transformer and rectified.




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weiming1998
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[*] posted on 20-1-2012 at 01:24


So a cell phone charger?
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[*] posted on 20-1-2012 at 17:31


Any wall adapter, some will be more powerful then others. They are the worst power source because there low voltage and low amps but its better then nothing when your in a pinch.




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[*] posted on 20-1-2012 at 18:06


Ok, thanks. Yesterday I combined 2 batches of dilute sulfuric acid. I boiled it down to 25mls, still not fuming! But all the waste in there has precipated (some has even carbonized.) I guess I would have a better yield if I electrolyzed copper sulfate.
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[*] posted on 20-1-2012 at 21:04


I'm going to have a go soon at making a SO2 solution and using Lead electrodes to convert it to H2SO4 to see if there is Viability in what I am pretty sure would be the cheapest and simplest method of performing this oxidation.




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[*] posted on 20-1-2012 at 21:20


Use CuSO4 solution instead. Lead cathode+copper anode? Becuase I tried making lead sulfate with copper sulfate and lead, and it didn't work. The lead barely got a copper plating. Also, PbSO4 is insoluble and heavy, easy to remove by filter/pouring off.
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[*] posted on 21-1-2012 at 13:08


Solutions of sodium sulfite in water can be spontaneously oxidized by air to sulfate, but I do not know if sulfur dioxide solutions can similarly be oxidized to dilute sulfuric acid.

But I found this:
Quote:

The air-oxidation of bisulfite can not be completely suppressed, and this appears to be the only factor pre- venting complete utilization of the bisulfite in sulfoacid.


Quote:

This is attributed to oxidation of bisulfite by air, but it is not clear why such incidental oxidation did not similarly affect the results for formaldehyde.

http://pubs.acs.org/doi/abs/10.1021/ac50092a021

Quote:

Sodium bisulfite solutions undergo oxidation on standing in air.

http://worldaccount.basf.com/wa/NAFTA/Catalog/ChemicalsNAFTA...

If bisulfite can be oxidized by air, then likely sulfurous acid can also be oxidized to sulfuric. But the concentration of sulfuric acid obtainable would in practice be very low, because lower pH would shift the equilibrium away from bisulfite.

SO2 + H2O <==> H2SO3 <==> HSO3[-] + H[+]aq
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weiming1998
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[*] posted on 21-1-2012 at 14:49


Yes, the concentration is extremely low. 1000mls of dilute acid can be condensed down into 25mls of somewhat concentrated acid.
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[*] posted on 21-1-2012 at 21:06


I think one electrode should be made of a porous conductive material so that the SO2 bubbles out into the solution through the electrode so that oxidation occurs as its being feed into the system.

Placing materials like Mn Sulfate and what not would generate per sulfates causing the oxidation to take place much more efficiently.





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[*] posted on 21-1-2012 at 21:26


Quote: Originally posted by Sedit  
I think one electrode should be made of a porous conductive material so that the SO2 bubbles out into the solution through the electrode so that oxidation occurs as its being feed into the system.

Placing materials like Mn Sulfate and what not would generate per sulfates causing the oxidation to take place much more efficiently.


I am probably now going to try electrolytic oxidation soon, but I am going to try a mixture of MnSO4 and FeSO4 for catalyst. Also, How much should I put in if I want it to act like a catalyst?
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[*] posted on 24-1-2012 at 13:35


Interestingly, Chlorine can be used to oxidize dilute Sulfurous acid:

H2SO3 + H2O + Cl2 --> H2SO4 + 2 HCl

Note, water is consumed and the solution becomes more acidic.

Chlorine can be generated by adding FeSO4 to Bleach (NaOCl/NaCl), but please comply with local laws.

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[*] posted on 24-1-2012 at 14:08


Quote: Originally posted by AJKOER  

Chlorine can be generated by adding FeSO4 to Bleach (NaOCl/NaCl), but please comply with local laws.


The incompatibility list of a material safety data sheet should never be mistaken for a laboratory preparation. Please do not share preparative advice that you cannot cite from a reputable source (e.g. a journal paper or scientific book, not Wikipedia or Loompanics) unless you have verified it yourself.




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[*] posted on 25-1-2012 at 06:26


Quote: Originally posted by Polverone  
Quote: Originally posted by AJKOER  

Chlorine can be generated by adding FeSO4 to Bleach (NaOCl/NaCl), but please comply with local laws.


The incompatibility list of a material safety data sheet should never be mistaken for a laboratory preparation. Please do not share preparative advice that you cannot cite from a reputable source (e.g. a journal paper or scientific book, not Wikipedia or Loompanics) unless you have verified it yourself.


OK, a few points.

First, the source of the method of employing FeSO4 is actually an old Sciencemadness thread (Topic: "Chlorine" LINK:
http://www.sciencemadness.org/talk/viewthread.php?tid=1305&a...) reputedly based on repeated direct observations. I apology for not citing it, but given the poor science per some of our participants, I did not place it (in concurrence with your point) in the league of a journal paper or scientific book. Our threads are, however, at times good in reporting observations and free of reporting bias if the mechanism of the reaction(s) is(are) uncertain.

To my knowledge, there is no mention in the literature and I do agree with you that the MSDS should not be the source of choice.

Interestingly in that thread, several of participants debated the precise chemistry. I, myself, have also attempted, via a several stage reaction, in my recent thread on using FeSO4 to prepare dilute H2SO4 (pardon my arrogance in assuming everyone had read it) to explore the chemistry. If you read one of my postulated explanations, however, based on a hypothetical reaction with an unstable/unknown Iron hypochlorite, you may surmise possibly why it is not in the main stream literature.

Also, I should mention, there is a Cl2 preparation via HCl/H2O2 and Al foil also in that same Sciencemadness thread. I have cited in a prior thread a YouTube video on this reaction (also not reported/recommended in the literature) and dared to explain the chemistry of why (pardon me again).



[Edited on 25-1-2012 by AJKOER]
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[*] posted on 25-1-2012 at 06:56


Why FeSO4, which is 10 dollars for 500 grams. Why not use NaHSO4, which is more effective/cheap when generating the gas? Unless you want the by-product of the generation?

Also, the decomposition is really bothering. Unless you can drive the HCl/Cl2 out of the solution, however, without driving the SO2 out as well. Maybe freezing in a cold freezer?

[Edited on 25-1-2012 by weiming1998]
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[*] posted on 25-1-2012 at 09:04


OK, per this link FeSO4, a common fertilizer, costs $60-80 / Metric ton (please comply with local laws). It is reputedly 98% pure!

http://www.alibaba.com/showroom/fertilizer-feso4.html

I should mention that in my previously cited method for the oxidation of H2SO3 via HIO3, I suggested the Iodine and water method:

I2 + H2O <---> HI + HIO

and rapidly: 3 HIO --> 2 HI + HIO3

where the Iodine is to be boiled in water until the solution becomes colorless. I also recommended adding O2 (via air or even H2O2) to convert the HI:

2 HI + H2O2 --> I2 + 2 H2O

and the reaction cycles to the beginning. For the record, the most recommended method is via adding Cl2 (see Wikipedia: http://en.wikipedia.org/wiki/Iodic_acid), but this results in HCl and HIO3.

But, per my route, it is not necessary to separate out the dissolved HIO3 since eventually all the Iodine is converted into HIO3 (aq).

Now, just treat the HIO3 solution with SO2 (or H2SO3):

5 H2SO3 + 2 HIO3 --> 5 H2SO4 + I2 + H2O

The reference cited below notes that the crude Iodine separates from the solution. Note, if we have excess H2SO3:

3 H2SO3 + HIO3 --> HI + 3H2SO4

so treating with O2 (or a little H2O2) also would remove any HI still remaining in solution (evident if solution gets darker after oxidation).

As an excellent reference: "Inorganic chemistry" by Egon Wiberg, Nils Wiberg, Arnold Frederick Holleman, pages 415-417. This good source discusses the extraction of Iodine, its solubility and applicable solvents.

http://books.google.com/books?id=Mtth5g59dEIC&pg=PA415&a...




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