塩化鉄(Ⅱ)四水和物

解説塩化鉄(Ⅱ)：FeCl2(126.75)．二塩化鉄ともいう．白～淡緑色のりん片状晶．潮解性があり，乾いた塩化水素中で鉄を赤熱すると得られる．密度2.99 g cm－3．融点672 ℃，沸点1024 ℃．常磁性をもつ．吸湿性で湿った空気中では，ただちに緑黄色を経て赤褐色になる．水に易溶．光により分解する．四水和物は淡緑色の結晶．潮解性．密度1.926 g cm－3．加熱すると水和水中に溶ける．媒染剤，廃水処理剤，冶金，医薬製造などに用いられる．[CAS 7758-94-3:FeCl2][CAS 16399-77-2:FeCl2･2H2O][CAS 13478-10-9:FeCl2･4H2O]塩化鉄(II)，化学式FeCl2。無水和物と2,4,6水和物が知られているが，市販のものはほぼ4水和物FeCl2･4H2Oに相当する。無水和物は白～淡緑白色の結晶で六方晶系に属し，塩化カドミウム型構造をとる。空気中で湿気を吸い赤褐色になる。4水和物は緑色，潮解性の結晶で単斜晶系に属する。その塩酸溶液を空気中に放置すると塩化鉄(III)に変化する。水やエチルアルコールによく溶け，水溶液から12.3℃以下で6水和物，76.5℃以上で2水和物が析出する。

用途染料、媒染剤、冶金、調剤、塩化鉄(III)の製造。

用途高純度金属化合物。

用途塩酸溶液を空気に放置すると酸素により酸化され塩化鉄(III)に変化する植物染料の媒染剤として用いる。

用途媒染剤、染料

使用Iron(II) chloride tetrahydrate is used as a reducing agent in metallurgy, in pharmaceutical preparations, as a mordant in dyeing and in sewage treatment. Ferrous chloride has a kind of niche application. During the laboratory synthesis of iron complexes, ferrous chloride acts as a reducing flocculating agent in waste water treatment, particularly for wastes containing chromate. It is the precursor to hydrated iron(III) oxides that are magnetic pigments. Ferrous chloride is employed as a reducing agent in many organic synthesis reactions.

一般的な説明Iron(II) chloride tetrahydrate is a hydrated metallic halide. Crystal structure studies suggest that it crystallizes in monoclinic system having space group P21/c.

純化方法A 550mL round-bottomed Pyrex flask is connected, via a glass tube fitted with a medium porosity sintered-glass disc, to a similar flask. To 240g of FeCl2.4H2O in the first flask is added conductivity water (200mL), 38% HCl (10mL), and pure electrolytic iron (8-10g). A stream of purified N2 gas is passed through the assembly, escaping through a mercury trap. The salt is dissolved by heating which is continued until complete reduction has occurred. By inverting the apparatus and filtering (under N2 pressure) through the sintered glass disc, unreacted iron is removed. After cooling and crystallisation, the unit is again inverted, and the crystals of ferrous chloride are filtered free from mother liquor by applied N2 pressure. Partial drying by overnight evacuation at room temperature gives a mixed hydrate which, on further evacuation on a water bath at 80o, loses water of hydration and absorbed HCl (with vigorous effervescence) to give a white powder of FeCl2.2H2O (see below). [Gayer & Wootner J Am Chem Soc 78 3944 1956, (2H2O) Gayer & Woontner Inorg Synth V 179 1957.]