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|Section2= |Section3= |Section4= }} Ammonium iron(III) sulfate, NH4Fe(SO4)2·12 H2O, or NH4()(SO4)2·6 H2O, also known as ferric ammonium sulfate (FAS) or iron alum, is a double salt in the class of alums, which consists of compounds with the general formula AB(SO4)2 · 12 H2O.〔Considine, Douglas M: ''Chemical and process technology encyclopedia'', McGraw-Hill, New York, 1974, p. 993〕 It has the appearance of weakly violet, octahedrical crystals. There has been some discussion regarding the origin of the crystals' colour, with some ascribing it to impurities in the compound, and others claiming it to be a property of the crystal itself. FAS is paramagnetic, acidic and toxic towards microorganisms.〔Fei Wang et al.: "Microcalorimetric investigation of the toxic action of ammonium ferric(III)sulfate on the metabolic activity of pure microbes" ''Accessible via http://www.sciencedirect.com''〕 It is a weak oxidizing agent, capable of being reduced to Mohr's salt, ferrous ammonium sulfate. ==Preparation== FAS can be prepared by crystallization from a solution of ferric sulfate and ammonium sulfate. Iron(II) in ferrous sulfate is oxidized to Iron(III) in ferric sulfate by addition of sulfuric and nitric acid. Upon addition of ammonium sulfate to the solution and damping in of the solution, ferric ammonium sulfate crystals will precipitate. Oxidation: 6 FeSO4 + 2 HNO3 + 3 H2SO4 = 3 Fe2(SO4)3 + 2 NO + 4 H2O Synthesis: Fe2(SO4)3 + (NH4)2SO4 = 2 NH4Fe(SO4)2 Procedure〔Hecht, Horstmar: ''Prãparative Anorganische Chemie'', ''Springer-Verlag, Berlin'', 1951. p. 127〕: The nitric and sulfuric acid is reacted with the ferrous sulfate to make ferric sulfate, nitric oxide, and water. The ferric sulfate is mixed with ammonium sulfate and crystallized to get ammonium iron(III) sulfate. The solution is normally tested to ensure that no more iron(II) is left. 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「Ammonium iron(III) sulfate」の詳細全文を読む スポンサード リンク
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