Wikipedia
Iron(III) chloride, also called ferric chloride, is an industrial scale commodity chemical compound, with the formula Fe Cl and with iron in the +3 oxidation state. The colour of iron(III) chloride crystals depends on the viewing angle: by reflected light the crystals appear dark green, but by transmitted light they appear purple-red. Anhydrous iron(III) chloride is deliquescent, forming hydrated hydrogen chloride mists in moist air. It is rarely observed in its natural form, mineral molysite, known mainly from some fumaroles.
When dissolved in water, iron(III) chloride undergoes hydrolysis and gives off heat in an exothermic reaction. The resulting brown, acidic, and corrosive solution is used as a flocculant in sewage treatment and drinking water production, and as an etchant for copper-based metals in printed circuit boards. Anhydrous iron(III) chloride is a fairly strong Lewis acid, and it is used as a catalyst in organic synthesis.
Iron(II) chloride, also known as ferrous chloride, is the chemical compound of formula FeCl. It is a paramagnetic solid with a high melting point, and is usually obtained as an off-white solid. FeCl crystallizes from water as the greenish tetrahydrate, which is the form that is most commonly encountered in commerce and the laboratory. There is also a dihydrate. The compound is also soluble in water; aqueous solutions of FeCl are yellow.
Iron chloride can refer to
- Iron(II) chloride (ferrous chloride, iron dichloride), FeCl
- Iron(III) chloride (ferric chloride, iron trichloride), FeCl