Potassium ferrate

Structural formula
General
Surname	Potassium ferrate
other names	Potassium ferrate (VI)
Molecular formula	K 2 FeO 4
Brief description	black solid
External identifiers / databases
CAS number 39469-86-8 PubChem 161995 Wikidata Q418315
properties
Molar mass	198.04 g · mol -1
Physical state	firmly
Melting point	> 400 ° C
solubility	easily soluble in water
safety instructions
GHS labeling of hazardous substances danger H and P phrases H: 272 P: 220
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Potassium ferrate (VI) is a purple-red to violet chemical compound that is stable in its pure form .

The ferrate (VI) ion (Fe ^VI O ₄ ²⁻ ) contains a tetrahedral iron atom surrounded by four oxygen atoms . It is a charge transfer complex , which explains the intense color.

In this compound, iron is in its highest oxidation state . Potassium ferrate is therefore a powerful oxidizing agent , stronger than potassium permanganate .

Extraction

For display in a laboratory is first sodium hydroxide by oxidation with chlorine gas in the hypochlorite transferred. This is then reacted with an iron (III) nitrate solution and the ferrate (VI) solution obtained is saturated with sodium hydroxide. The potassium ferrate is finally precipitated from this solution with concentrated potassium hydroxide solution . The compound can be obtained in a purity of> 98% by reprecipitation from concentrated potassium hydroxide solution:

${\displaystyle {\ce {2 NaOH + Cl2 -> NaCl + NaOCl + H2O}}}$

${\displaystyle {\ce {3 NaOCl + 2 Fe(NO3)3 * 9 H2O + 10 NaOH -> 2 Na2FeO4 + 6 NaNO3 + 3 NaCl + 23 H2O}}}$

${\displaystyle {\ce {Na2FeO4 + 2 KOH -> K2FeO4 + 2 NaOH}}}$

Other methods use potassium peroxodisulphate instead of chlorine as an oxidizing agent or do without the use of chemical oxidizing agents altogether and use electrolysis for this.

properties

Potassium ferrate (VI) in aqueous solution.

Potassium ferrate crystallizes in an orthorhombic crystal structure with the space group Pnam (space group no. 62, position 6) . The lattice constants are a = 769 pm, b = 1033 pm and c = 586 pm. The structure is isomorphic to that of potassium sulfate and potassium chromate . The connection is only durable when dry. Very dilute solutions are stable for some time, while concentrated solutions decompose quickly.

Individual evidence

1. ↑ ^{a b c d} Data sheet Potassium ferrate (VI) from Sigma-Aldrich , accessed on April 6, 2011 ( PDF ).
2. ↑ ^{a b c d} Georg Brauer: Kaliumferrat (VI) . In: Handbook of Preparative Inorganic Chemistry . Ferdinand Enke Verlag, Stuttgart 1954, p. 1124-1126 .
3. ^ ML Hoppe, EO Schlemper, RK Murmann: Structure of Dipotassium Ferrate (Vl) , in: Acta Crystallographica , 1982, B38, 2237-2239, doi : 10.1107 / S0567740882008395

Web links

• US patent 5746994