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:''For the community in California, see Oleum, California.'' Oleum (Latin ''oleum'' = "oil"), or fuming sulfuric acid, is a solution of various compositions of sulfur trioxide in sulfuric acid, or sometimes more specifically to disulfuric acid (also known as pyrosulfuric acid). Oleums can be described by the formula ''y''SO3.H2O where y is the total molar sulfur trioxide content. The value of ''y'' can be varied, to include different oleums. They can also be described by the formula H2SO4.''x''SO3 where x is now defined as the molar free sulfur trioxide content. Oleum is generally assessed according to the free SO3 content by weight. 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.''0.13611''SO3, ''1.0225''SO3.H2O or 102.25% sulfuric acid. The conversion between % acid and % oleum is: % acid = 100 + 18/80 * % oleum A value for ''x'' of 1 gives us the empirical formula H2S2O7 for disulfuric (pyrosulfuric) acid. Pure disulfuric acid itself is a solid at room temperature, melting at 36 °C and rarely used either in the laboratory or industrial processes. ==Production== Oleum is produced in the contact process, where sulfur is oxidized to sulfur trioxide which is subsequently dissolved in concentrated sulfuric acid. Sulfuric acid itself is regenerated by dilution of part of the oleum. The lead chamber process for sulfuric acid production was abandoned partly because it could not produce sulfur trioxide or concentrated sulfuric acid directly due to corrosion of the lead, and absorption of NO2 gas. Until this process was made obsolete by the contact process, oleum had to be obtained through indirect methods. Historically, the biggest production of oleum came from the distillation of iron sulfates at Nordhausen, from which the historical name Nordhausen sulfuric acid is derived. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Oleum」の詳細全文を読む スポンサード リンク
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