Ammonium trioxalato ferrate (III)

Structural formula
General
Surname	Ammonium trioxalato ferrate (III) trihydrate
other names	Ammonium iron (III) oxalate trihydrate Ferric ammonium oxalate Ammonium iron oxalate
Molecular formula	(NH 4 ) 3 [Fe (C 2 O 4 ) 3 ] • 3 H 2 O
Brief description	green, photosensitive crystals
External identifiers / databases
CAS number 2944-67-4 14221-47-7 (anhydrous) 13268-42-3 (trihydrate) EC number 238-090-0 ECHA InfoCard 100.034.612 PubChem 62468 ChemSpider 24761 Wikidata Q5445333
properties
Molar mass	374.017 g · mol -1 (anhydrous) 428.06 g mol −1 (trihydrate)
Physical state	firmly
density	1.78 g cm −3
Melting point	160–170 ° C (decomposition)
solubility	soluble in water
safety instructions
GHS labeling of hazardous substances Caution H and P phrases H: 302-312 P: 280
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Ammonium trioxalato ferrate (III) is a complex of trivalent iron with oxalate anions as ligands and ammonium ions for charge compensation. As a trihydrate, it has the semi-structural formula (NH ₄ ) ₃ [Fe (C ₂ O ₄ ) ₃ ] · 3 H ₂ O. The EC number is 2209522.

Extraction and presentation

Ammonium trioxalato ferrate (III) can be obtained by reacting iron (III) chloride solution with ammonium oxalate in an aqueous solution. The trihydrate is always obtained:

${\displaystyle \mathrm {FeCl_{3}+3\ {(NH_{4})}_{2}C_{2}O_{4}+3\ H_{2}O\longrightarrow {(NH_{4})}_{3}[{Fe(C_{2}O_{4})}_{3}]\cdot 3\ H_{2}O+3\ NH_{4}Cl} }$

properties

Ammonium trioxalato ferrate (III)

Ammonium trioxalato ferrate (III) is a green crystalline compound that is readily soluble in water.

The Fe ³⁺ - ion is octahedral three oxalato dianions complexed . The resulting charge of −3 on the complex is compensated for by three ammonium ions.

use

It is used in the anodising process, the surface treatment of aluminum , to create a gold tone.

Exposure to light leads to decomposition with the formation of carbon dioxide and iron (II) compounds. Because of this property, it can be used for light measurement . In artistic photography it is part of the solution for making cyanotypes .

Individual evidence

1. ↑ ^{a b c} Entry on ammonium iron (III) oxalate. In: Römpp Online . Georg Thieme Verlag, accessed on September 29, 2014.
2. ↑ Data sheet ammonium trioxalato ferrate (III) from AlfaAesar, accessed on March 14, 2010 ( PDF )(JavaScript required) .
3. ↑ ^{a b} Entry on ammonium iron (III) oxalate, trihydrate in the GESTIS substance database of the IFA , accessed on February 13, 2017(JavaScript required) .