Iron hydroxide - Suisancatetsu

[ I ] Iron(II) hydroxide: Fe(OH) ₂ (89.86). Obtained by adding sodium hydroxide to an aqueous solution of iron(II) salt from which oxygen has been completely removed. White to pale green powder. Density: 3.40 g cm ^-3 . Extremely susceptible to oxidation; in aqueous solution it is gradually oxidized by dissolved oxygen, while in air it is oxidized immediately by heat to form reddish-brown iron(III) hydroxide. Hardly soluble in water. Dissolves in concentrated alkali hydroxide to form tetrahydroxoferrate(II) salt M ^Ⅰ ₂ [Fe(OH) ₄ ]. Insoluble in ethanol and ether. Used to make black lacquer. [CAS 18624-44-7] [ II ] Iron(II) hydroxide, iron(III): Fe ₃ O ₄ ･ n H ₂ O. Obtained by adding ammonia water to an aqueous solution of iron(II) oxide, iron(III). Black powder. Ferromagnetic and easily oxidized. When heated in air, it becomes iron(III) oxide. Soluble in hydrochloric acid and concentrated sulfuric acid, easily soluble in dilute nitric acid, and sparingly soluble in concentrated nitric acid. [ III ] Iron(III) _hydroxide : _Fe2O3 ･ _H2O ( _177.70 ), or FeO(OH) (88.85). Also called iron(III) oxide hydroxide. The dark red cotton-like solid obtained by adding ammonia water or alkali to an aqueous solution of iron(III) is represented as _Fe2O3 ･ nH2O with variable water content. It is an amorphous _hydroxide . Fe(OH) ₃ does not exist, so it is a misnomer. Sparingly soluble in water. Easily forms colloidal solutions. The newly precipitated material is highly adsorptive _{and amphoteric. When dried, it becomes FeO(OH) and then Fe2O3 .} Those with a definite composition are _Fe2O3 ･ _{H2O or} FeO(OH), and there are α and γ forms. The α form is a pale yellow mass. Density 3.3-4.3 g cm ^-3 . Soluble in acid, insoluble in water. At 600 °C it becomes α-Fe ₂ O ₃ . The γ form is a yellow powder. Density 4.09 g cm ^-3 . At 400 °C it becomes γ-Fe ₂ O ₃ . The important iron ore limonite is Fe ₂ O ₃ ･ n H ₂ O, a mixture of these modifications. Used as a yellow pigment, an antidote for arsenic poisoning, and as a raw material for medicines. [CAS 20344-49-4:FeO(OH)][CAS 1309-33-7:Fe(OH) ₃ ]

Source: Morikita Publishing "Chemical Dictionary (2nd Edition)" Information about the Chemical Dictionary 2nd Edition

【Ⅰ】水酸化鉄(Ⅱ)：Fe(OH)₂(89.86)．酸素を完全に除いた鉄(Ⅱ)塩水溶液に水酸化ナトリウムを加えると得られる．白～淡緑色の粉末．密度3.40 g cm^－3．きわめて酸化されやすく，水溶液では溶存酸素により徐々に，空気中ではただちに熱を発して酸化され，赤褐色の水酸化鉄(Ⅲ)になる．水に難溶．濃水酸化アルカリにはテトラヒドロキソ鉄(Ⅱ)酸塩M^Ⅰ₂[Fe(OH)₄]をつくって溶ける．エタノール，エーテルに不溶．黒うるしの製造に用いられる．[CAS 18624-44-7]【Ⅱ】水酸化鉄(Ⅱ)鉄(Ⅲ)：Fe₃O₄･nH₂O．酸化鉄(Ⅱ)鉄(Ⅲ)の塩酸水溶液にアンモニア水を加えると得られる．黒色の粉末．強磁性で，酸化されやすい．空気中で加熱すると酸化鉄(Ⅲ)になる．塩酸，濃硫酸に可溶，希硝酸に易溶，濃硝酸に難溶．【Ⅲ】水酸化鉄(Ⅲ)：Fe₂O₃･H₂O(177.70)，またはFeO(OH)(88.85)．酸化水酸化鉄(Ⅲ)ともいう．鉄(Ⅲ)水溶液にアンモニア水あるいはアルカリを加えて得られる暗赤色の綿状固体は，含水量不定のFe₂O₃･nH₂Oで表される．無定形水酸化物である．Fe(OH)₃は存在せず，誤称である．水に難溶．コロイド溶液になりやすい．新しく沈殿したものは吸着性が強く，また両性である．乾燥するとFeO(OH)を経て，Fe₂O₃になる．一定の組成をもつものはFe₂O₃･H₂OまたはFeO(OH)で，α形とγ形がある．α形は淡黄色の塊．密度3.3～4.3 g cm^－3．酸に可溶，水に不溶．600 ℃ でα-Fe₂O₃になる．γ形は黄色の粉末．密度4.09 g cm^－3．400 ℃ でγ-Fe₂O₃になる．重要な鉄鉱石の褐鉄鉱はFe₂O₃･nH₂Oで，これらの変態の混合物である．黄色顔料，ヒ素中毒の解毒剤，医薬品の原料などに用いられる．[CAS 20344-49-4:FeO(OH)][CAS 1309-33-7:Fe(OH)₃]

出典　森北出版「化学辞典（第2版）」化学辞典 第2版について　情報