Iron(III) nitrate, or ferric nitrate, is the name used for a series of

inorganic compound In chemistry, an inorganic compound is typically a chemical compound that lacks carbon–hydrogen bonds, that is, a compound that is not an organic compound. The study of inorganic compounds is a subfield of chemistry known as ''inorganic chemistr ...

s with the formula Fe(NO₃)₃^.(H₂O)_n. Most common is the nonahydrate Fe(NO₃)₃^.(H₂O)₉. The hydrates are all pale colored, water-soluble paramagnetic salts.

Hydrates

Iron(III) nitrate is

deliquescent Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature. If water molecules become suspended among the substance ...

, and it is commonly found as the nonahydrate Fe(NO₃)₃· 9H₂O, which forms colourless to pale violet crystals. This compound is the trinitrate salt of the

aquo complex In chemistry, metal aquo complexes are coordination compounds containing metal ions with only water as a ligand. These complexes are the predominant species in aqueous solutions of many metal salts, such as metal nitrates, sulfates, and perchlorat ...

e(H₂O)₆sup>3+. Other

hydrates In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was unders ...

·''x'', include: * tetrahydrate (''x''=4), more precisely triaqua dinitratoiron(III) nitrate monohydrate, ·, has complex cations where atom is coordinated with two nitrate anions as bidentate ligands and three of the four water molecules, in a

pentagonal bipyramid In geometry, the pentagonal bipyramid (or dipyramid) is third of the infinite set of face-transitive bipyramids, and the 13th Johnson solid (). Each bipyramid is the dual of a uniform prism. Although it is face-transitive, it is not a Platoni ...

configuration with two water molecules at the poles.H. Schmidt, A. Asztalos, F. Bok and W. Voigt (2012): "New iron(III) nitrate hydrates: ·''x'' with ''x'' = 4, 5 and 6". ''Acta Crystallographica Section C - Inorganic Compounds'', volume C68, pages i29-i33. * pentahydrate (''x''=5), more precisely penta-aqua nitratoiron(III) dinitrate, , in which the atom is coordinated to five water molecules and a unidentate nitrate anion ligand in octahedral configuration. * hexahydrate (''x''=6), more precisely hexaaquairon(III) trinitrate, , where the atom is coordinated to six water molecules in octahedral configuration.

Chemical properties

Decomposition

When dissolved, iron(III) nitrate forms yellow solution due to hydrolysis. When heated to near boiling, nitric acid will evaporate from the solution, and all the iron will precipitate as

iron(III) oxide Iron(III) oxide or ferric oxide is the inorganic compound with the formula Fe2O3. It is one of the three main oxides of iron, the other two being iron(II) oxide (FeO), which is rare; and iron(II,III) oxide (Fe3O4), which also occurs naturally ...

.Egon Matijević and Paul Scheiner (1978): "Ferric hydrous oxide sols: III. Preparation of uniform particles by hydrolysis of Fe(III)-chloride, -nitrate, and -perchlorate solutions". ''Journal of Colloid and Interface Science'', volume 63, issue 3, pages 509-524. The compound will dissolve in molten stearic acid and decompose at about 120 °C to give

iron(III) oxide-hydroxide Iron(III) oxide-hydroxide or ferric oxyhydroxideA. L. Mackay (1960): "β-Ferric Oxyhydroxide". ''Mineralogical Magazine'' (''Journal of the Mineralogical Society''), volume 32, issue 250, pages 545-557. is the chemical compound of iron, oxygen, ...

.Dan Li, Xiaohui Wang, Gang Xiong, Lude Lu, Xujie Yang and Xin Wang (1997): "A novel technique to prepare ultrafine via hydrated iron(III) nitrate". ''Journal of Materials Science Letters'' volume 16, pages 493–495

Preparation

The compound can be prepared by treating

iron Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in fr ...

metal powder with

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitric ...

. : Fe + 4 HNO₃ → Fe(NO₃)₃ + NO + 2 H₂O.

Applications

Ferric nitrate has no large scale applications. It is a catalyst for the synthesis of

sodium amide Sodium amide, commonly called sodamide (systematic name sodium azanide), is the inorganic compound with the formula . It is a salt composed of the sodium cation and the azanide anion. This solid, which is dangerously reactive toward water, is white ...

from a solution of

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable is ...

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...

: : 2 NH₃ + 2 Na → 2 NaNH₂ + H₂ Certain

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2 Si2 O5( OH)4). Clays develop plasticity when wet, due to a molecular film of water surrounding the clay parti ...

s impregnated with ferric nitrate have been shown to be useful oxidants in

organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...

. For example, ferric nitrate on

Montmorillonite Montmorillonite is a very soft phyllosilicate group of minerals that form when they precipitate from water solution as microscopic crystals, known as clay. It is named after Montmorillon in France. Montmorillonite, a member of the smectite group ...

—a

reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...

called "Clayfen"—has been employed for the oxidation of

alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

s to

aldehyde In organic chemistry, an aldehyde () is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred to as an aldehyde but can also be classified as a formyl group ...

s and

thiol In organic chemistry, a thiol (; ), or thiol derivative, is any organosulfur compound of the form , where R represents an alkyl or other organic substituent. The functional group itself is referred to as either a thiol group or a sulfhydryl grou ...

s to

disulfide In biochemistry, a disulfide (or disulphide in British English) refers to a functional group with the structure . The linkage is also called an SS-bond or sometimes a disulfide bridge and is usually derived by the coupling of two thiol groups. In ...

s.Cornélis, A. Laszlo, P.; Zettler, M. W. "Iron(III) Nitrate–K10 Montmorillonite Clay" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. . Ferric nitrate solutions are used by jewelers and metalsmiths to etch silver and silver alloys.

References

{{nitrates Iron(III) compounds Nitrates Deliquescent substances Oxidizing agents