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weiming1998
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Quote: Originally posted by dann2  |
What impurities would Camden tablets (Sodium Metabisulphite for wine making) contain.
Would it effect SO2 making using the tablets + Sulphuric acid
Could other acids be used instead of Sulphuric?
Dann2 |
I don't know about impurities, but they wouldn't really matter that much. Most impurities probably won't affect the SO2 made, but that depends on what
acids you use. If there is chlorides in your winemaking tablets, for example, and you use sulfuric acid, the resulting evolution of HCl gas will ruin
your SO2.
Sulfuric acid isn't actually a good candidate acid for generating SO2, as other soluble gases generated might contaminate the SO2, and also the fact
that SO2 dissolves in sulfuric acid more than water. So your best acid choice would be HCl solution, as that prevents the formation of hydrogen
halides.
But almost all acids work (well, apart from a few exceptions that are extremely weak acids/oxidizing acids like HNO3, which will oxidize the SO2
produced to sulfuric acid, and HClO/H2CO3, which almost certainly doesn't work) by this equation: Na2S2O5(s/aq)+2H+(aq?)==>2SO2(g)+H2O+2Na+(aq).
The SO2 exits the solution as a gas, making this reaction favourable, so even weak acids (like acetic acid) works. But not a dilute solution though
(if you used vinegar, the yield will not be great compared to if you used 25% acetic acid.)
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dann2
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Thanks for reply.
I might get around to trying it some time as I need to clear away all Chlorate from Perchlorate that I have using SO2.
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woelen
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After reading over this whole thread I now think that the formation of SO2 from H2SO4 and S maybe due to organic impurities in the S. This also could
account for the black coloration of the acid, reported by some people. I did not know of that kind of impurities back in 2007, but recently I have
seen some posts about sulphur from gardening suppliers containing organic impurities, leading to charring when the sulphur is heated. I also read that
some sources of sulphur may contain small amounts of CaCO3, which also may cause bubbling (CO2).
I still am convinced that very pure sulphur and pure sulphuric acid only react with difficulty making SO2.
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elementcollector1
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I saw you mentioned on the first page that your CrO3 decomposed to oxygen and a green Cr(III) compound. That was chromium (III) oxide. How did you
make your CrO3 from K2Cr2O7 and H2SO4, anyway?
Also, for production of SO2 from sulfuric acid, what about electrolysis? This could even work for sulfates.
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woelen
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I did not isolate CrO3. This compound simply is formed when chromates or dichromates are mixed with conc. H2SO4.
E.g. K2Cr2O7 + 2H2SO4 --> 2KHSO4 + H2O + 2CrO3
This reaction also works with very concentrated solutions. E.g. if you prepare a saturated solution of Na2Cr2O7 and pour in conc. H2SO4, then a dark
red slurry of CrO3 is formed. This material, however, is very hard to isolate.
For my experiment there was no need to isolate the CrO3, it simply was in solution and reacted with the sulphur.
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Electrolysis of solutions of sulfates or aqueous sulphuric acid does not lead to formation of SO2. At the anode you get oxidation of the anode
material, or formation of oxygen if the anode is inert and at the cathode you get hydrogen gas.
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elementcollector1
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What makes it hard to isolate? Does filtration or decanting the excess liquid not work for whatever reason?
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UnintentionalChaos
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Hygroscopic, corrosive, highly water soluble, sets a number of organic solvents on fire on contact. You need to remove the fairly concentrated
sulfuric acid from the product somehow.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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