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| Identifiers | |
|---|---|
| ECHA InfoCard | 100.116.872 |
| EC Number |
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CompTox Dashboard (EPA)
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| Properties | |
| H2S2O7 | |
| Appearance | colorless fuming liquid |
| Related compounds | |
Related compounds
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sulfuric acid sulfur trioxide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Oleum (Latin oleum, meaning oil), or fuming sulfuric acid, is a term referring to solutions of various compositions of sulfur trioxide in sulfuric acid, or sometimes more specifically to disulfuric acid (also known as pyrosulfuric acid).[1]
Oleums can be described by the formula ySO3·H2O where y is the total molar mass of sulfur trioxide content. The value of y can be varied, to include different oleums. They can also be described by the formula H2SO4·xSO3 where x is now defined as the molar free sulfur trioxide content. Oleum is generally assessed according to the free SO3 content by mass. It can also be expressed as a percentage of sulfuric acid strength; for oleum concentrations, that would be over 100%. For example, 10% oleum can also be expressed as H2SO4·0.13611SO3, 1.13611SO3·H2O or 102.25% sulfuric acid. The conversion between % acid and % oleum is:
For x = 1 and y = 2 the empirical formula H2S2O7 for disulfuric (pyrosulfuric) acid is obtained. Pure disulfuric acid is a solid at room temperature, melting at 36 °C and rarely used either in the laboratory or industrial processes — although recent research indicates that pure disulfuric acid has never been isolated yet.[2]
- ^ Hinds, John Iredelle Dillard (January 1902). Inorganic Chemistry: With the Elements of Physical and Theoretical Chemistry. J. Wiley & sons.
- ^ Kim, Seong Kyu; Lee, Han Myoung; Kim, Kwang S. (28 October 2015). "Disulfuric acid dissociated by two water molecules: ab initio and density functional theory calculations". Physical Chemistry Chemical Physics. 17 (43): 28556–28564. Bibcode:2015PCCP...1728556K. doi:10.1039/C5CP05201G. PMID 26400266.