Iron(III) nitrate

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

Iron(III) nitrate
Iron(III) nitrate nonahydrate
Names
IUPAC name
Iron(III) nitrate
Other names
Ferric nitrate
Nitric acid, iron(3+) salt
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.030.805
RTECS number
  • NO7175000
UNII
  • InChI=1S/Fe.3NO3.9H2O/c;3*2-1(3)4;;;;;;;;;/h;;;;9*1H2/q+3;3*-1;;;;;;;;; checkY
    Key: SZQUEWJRBJDHSM-UHFFFAOYSA-N checkY
  • InChI=1/Fe.3NO3.9H2O/c;3*2-1(3)4;;;;;;;;;/h;;;;9*1H2/q+3;3*-1;;;;;;;;;
    Key: SZQUEWJRBJDHSM-UHFFFAOYAC
  • [Fe+3].O.O.O.O.O.O.O.O.O.O=[N+]([O-])[O-].[O-][N+]([O-])=O.[O-][N+]([O-])=O
Properties
Fe(NO3)3
Molar mass 403.999 g/mol (nonahydrate)
241.86 g/mol (anhydrous)
Appearance Pale violet crystals
hygroscopic
Density 1.68 g/cm3 (hexahydrate)
1.6429 g/cm3(nonahydrate)
Melting point 47.2 °C (117.0 °F; 320.3 K) (nonahydrate)
Boiling point 125 °C (257 °F; 398 K) (nonahydrate)
150 g/100 mL (hexahydrate)
Solubility soluble in alcohol, acetone
+15,200.0·10−6 cm3/mol
Structure
octahedral
Hazards[1]
GHS labelling:
Ox. sol. 3Acute tox. 4 (oral); Eye irrit. 1[2]
Warning
H272, H302, H319
P210, P220, P221, P264, P270, P280, P301+P312, P305+P351+P338, P330, P337+P313, P370+P378, P501
NFPA 704 (fire diamond)
NFPA 704 four-colored diamond
1
0
0
OX
Flash point non-flammable
NIOSH (US health exposure limits):
REL (Recommended)
 TWA 1 mg/m3[3]
Safety data sheet (SDS) External SDS
Related compounds
Other anions
 Iron(III) chloride
Iron(III) sulfate
Related compounds
 Iron(II) nitrate
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
☒N verify (what is checkY☒N ?)
Infobox references

Hydrates

Iron(III) nitrate is deliquescent, 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 [Fe(H2O)6]3+.[4] Other hydrates Fe(NO
3)
3·xH
2O, include:

  • tetrahydrate (x=4), more precisely triaqua dinitratoiron(III) nitrate monohydrate, [Fe(NO3)2(H2O)3]NO3·H2O, 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 configuration with two water molecules at the poles.[5]
  • pentahydrate (x=5), more precisely penta-aqua nitratoiron(III) dinitrate, [Fe(NO3)(H2O)5](NO3)2, in which the Fe3+ ion is coordinated to five water molecules and a unidentate nitrate anion ligand in octahedral configuration.[5]
  • hexahydrate (x=6), more precisely hexaaquairon(III) trinitrate, [Fe(H2O)6](NO3)3, where the Fe3+ ion is coordinated to six water molecules in octahedral configuration.[5]

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 K2FeO4.[6]

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 Fe
2O
3 appears.[7] Another method for producing iron oxides from this nitrate salt involves neutralizing its aqueous solutions.[8]

Preparation

The compound can be prepared by treating iron metal powder with nitric acid, as summarized by the following idealized equation:[9]

Fe + 4 HNO3 + 7 H2O → Fe(NO3)3(H2O)9 + NO

Applications

Ferric nitrate has no large scale applications. It is a catalyst for the synthesis of sodium amide from a solution of sodium in ammonia:[10]

2 NH3 + 2 Na → 2 NaNH2 + H2

Certain clays impregnated with ferric nitrate have been shown to be useful oxidants in organic synthesis. For example, ferric nitrate on Montmorillonite—a reagent called Clayfen—has been employed for the oxidation of alcohols to aldehydes and thiols to disulfides.[11]

Ferric nitrate solutions are used by jewelers and metalsmiths to etch silver and silver alloys.

References
  1. HSNO Chemical Classification Information Database, New Zealand Environmental Risk Management Authority, retrieved 2010-09-19.
  2. "Iron(III) Nitrate Nonahydrate". American Elements. Retrieved June 20, 2019.
  3. NIOSH Pocket Guide to Chemical Hazards. "#0346". National Institute for Occupational Safety and Health (NIOSH).
  4. Hair, Neil J.; Beattie, James K. (1977). "Structure of Hexaaquairon(III) Nitrate Trihydrate. Comparison of Iron(II) and Iron(III) Bond Lengths in High-Spin Octahedral Environments". Inorganic Chemistry. 16 (2): 245–250. doi:10.1021/ic50168a006.
  5. H. Schmidt, A. Asztalos, F. Bok and W. Voigt (2012): "New Iron(III) Nitrate Hydrates: Fe(NO3|3·xH2O with x = 4, 5 and 6". Acta Crystallographica Section C - Inorganic Compounds, volume C68, pages i29-i33. doi:10.1107/S0108270112015855
  6. H. Lux (1963). "Potassium Ferrate (VI) K2FeO4". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY,NY: Academic Press. p. 1504.
  7. 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. doi:10.1016/S0021-9797(78)80011-3
  8. H. Lux (1963). "Iron (III) Hydroxide FeO(OH)". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY,NY: Academic Press. p. 1499.
  9. Wildermuth, Egon; Stark, Hans; Friedrich, Gabriele; Ebenhöch, Franz Ludwig; Kühborth, Brigitte; Silver, Jack; Rituper, Rafael. "Iron Compounds". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH.
  10. Hampton, K. G.; Harris, T. M.; Hauser, C. R. (1973). "2,4-Nonanedione". Organic Syntheses.; Collective Volume, vol. 5, p. 848 As of 2007, 22 other entries describe similar preparations in Organic Syntheses
  11. 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. doi:10.1002/047084289X.
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