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

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

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 (chemistry), absorption or adsorption from the surrounding Natural environment, environment, which is usually at normal or room temperature. If water mol ...

, 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 understo ...

·''x'', include: * tetrahydrate (''x''=4), more precisely triaqua dinitratoiron(III) nitrate monohydrate, , has complex cations wherein Fe³⁺ is coordinated with two nitrate anions as bidentate ligands and three of the four water molecules, in a

pentagonal bipyramid The pentagonal bipyramid (or pentagonal dipyramid) is a polyhedron with ten triangular faces. It is constructed by attaching two pentagonal pyramids to each of their bases. If the triangular faces are equilateral, the pentagonal bipyramid is an ...

configuration with two water molecules at the poles.H. Schmidt, A. Asztalos, F. Bok and W. Voigt (2012): "New Iron(III) Nitrate Hydrates: 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 Fe³⁺ ion 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 Fe³⁺ ion is coordinated to six water molecules in octahedral configuration.

Reactions

Iron(III) nitrate is a useful precursor to other iron compounds because the nitrate is easily removed or decomposed. It is for example, a standard precursor to

potassium ferrate Potassium ferrate is an inorganic compound with the formula . It is the potassium salt of ferric acid. Potassium ferrate is a powerful oxidizing agent with applications in green chemistry, organic synthesis, and cathode technology. Synthesis Gen ...

. When dissolved, iron(III) nitrate forms yellow solutions. When this solution is heated to near boiling, nitric acid evaporates and a solid precipitate of

iron(III) oxide Iron(III) oxide or ferric oxide is the inorganic compound with the formula . It occurs in nature as the mineral hematite, which serves as the primary source of iron for the steel industry. It is also known as red iron oxide, especially when use ...

appears.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. Another method for producing iron oxides from this nitrate salt involves neutralizing its aqueous solutions.

Preparation

The compound can be prepared by treating

iron Iron is a chemical element; it has symbol Fe () 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, forming much of Earth's o ...

metal powder with

nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...

, as summarized by the following idealized equation: :

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 whit ...

from a solution of

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

ammonia Ammonia is an inorganic chemical compound of nitrogen and hydrogen with the chemical formula, formula . A Binary compounds of hydrogen, stable binary hydride and the simplest pnictogen hydride, ammonia is a colourless gas with a distinctive pu ...

: : Certain

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

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

organic synthesis Organic synthesis is a branch of chemical synthesis concerned with the construction of organic compounds. Organic compounds are molecules consisting of combinations of covalently-linked hydrogen, carbon, oxygen, and nitrogen atoms. Within the gen ...

. 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 grou ...

—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 may refer to: Common uses * Alcohol (chemistry), a class of compounds * Ethanol, one of several alcohols, commonly known as alcohol in everyday life ** Alcohol (drug), intoxicant found in alcoholic beverages ** Alcoholic beverage, an alco ...

s to

aldehyde In organic chemistry, an aldehyde () (lat. ''al''cohol ''dehyd''rogenatum, dehydrogenated alcohol) is an organic compound containing a functional group with the structure . The functional group itself (without the "R" side chain) can be referred ...

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 chemistry, a disulfide (or disulphide in British English) is a compound containing a functional group or the anion. The linkage is also called an SS-bond or sometimes a disulfide bridge and usually derived from two thiol groups. In inorg ...

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 materials Oxidizing agents