dicyanin
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acidifying pyrosulfate with sulfuric acid in an attempted oleum substitute?
Hi,
It is posssible to obtain sodium or potassium pyrosulfate in varying amounts of purity, either by heating sodium/potassium bisulfate (Na- or KHSO4)
above its melting point for a prolonged time:
2 KHSO4 ---> K2S2O7 + H2O
or there are other ways to be found at the patent office, one patent I encountered used (from top of my head, don't have my notes with me) bubbling
sulfur dioxide gas (SO2) into a solution of NaOH/KOH in presence of a Cu(II) salt as oxidant. I know however that patents will often contain
nonsensical claims, especially the younger they are.
These methods have been discussed here before:
http://www.sciencemadness.org/talk/viewthread.php?tid=72323
Another one would be the oxidation of commercially available potassium metabisulfite (wine making) with concentrated nitric acid:
K2S2O5+2HNO3——>K2S2O7+NO+NO2+H2O
The question is, is it possible acidify an alkali metal pyrosulfate salt with concentrated H2SO4? It should form "pyrosulfuric acid" which is an
equimolar mixture of H2SO4 and SO3.
Commonly the late 19th century, early 20th century papers that use H2SO4 as an oxidising agent, use low strength oleum instead. I assume because the
low quantities of SO3 assure anhydrous conditions.
[Edited on 30-10-2020 by dicyanin]
sic transit gloria mundi
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macckone
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This is going to depend on a number of factors that I don't have answers to.
The relative solubilities of potassium pyrosulfate and potassium sulfate in sulfuric acid/oleum.
The heat of formation of both sides of the equilibrium.
How sensitive the end reaction is to potassium contamination.
If you are just trying to ensure the reaction is dry then yes it will work.
Otherwise the above factors are important.
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symboom
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pyrosulfate decomposes above 460 °C to sodium sulfate, releasing SO3.
There are reports that heating sodium pyrosulfate with concentrated sulfuric acid to 150°C results in SO3 and bisulfate.
[Edited on 30-10-2020 by symboom]
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Bedlasky
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If you want to make oleum in situ, try add phosphorus pentoxide or metaphosphate in to conc. sulfuric acid. I don't have P4O10, but I will to try
metaphosphate method for few test tube reactions in oleum. Metaphosphate can be easily made by heating dihydrogenphosphate or hydrogenphosphate.
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