Sodium ferrate
| Names | |
|---|---|
| IUPAC name
Sodium ferrate
| |
| Preferred IUPAC name
Sodium ferrate | |
| Systematic IUPAC name
Sodium ferrate (VI) | |
| Properties | |
| Na2FeO4 | |
| Appearance | Red-purple (solution) |
| Melting point | Decomposes |
| Boiling point | Decomposes |
| Very soluble | |
| Solubility | Reacts with various organic solvents |
| Hazards | |
| Safety data sheet | None |
| Flash point | Non-flammable |
| Related compounds | |
| Related compounds
|
Potassium ferrate |
| Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
| Infobox references | |
Sodium ferrate is a compound with a formula of Na2FeO4. It is a very elusive sodium salt of ferric acid. Ferric acid is extremely unstable and does not exist under normal conditions in any way, shape, form or concentration. Its salts also tend to be unstable, sodium ferrate in particular.
Contents
Properties
Physical
Those chosen few who have seen sodium ferrate as a dry solid, describe it similarly to potassium ferrate: a dark crystalline solid that dissolves in water to form red-purple solutions. Sodium ferrate is extremely soluble, and this is the reason why it is so hard to isolate it as a pure solid: it cannot be displaced from the solution by excess NaOH. Other methods of crystallization, such as boiling the solution down, are too harsh for the unstable ferrate ion, and tend to decompose it completely.
Chemical
Sodium ferrate is a very strong oxidizer, stronger and more reactive than potassium ferrate. Generally, however, their properties are similar.
Availability
This is an exceptionally rare chemical, it is usually not stocked by any major suppliers, including Sigma-Aldrich.
Preparation
It is relatively easy to prepare an aqueous solution of sodium ferrate: the same two methods that are used for synthesizing potassium ferrate, namely the electrolytic method and the hypochlorite method, will work here. However, the resulting red-purple solution is more or less a dead end: there's no way to turn it into the pure solid in an amateur setting.
Another, non-aqueous way to prepare this compound involves a precursor chemical, sodium ferrate (IV), or sodium hypoferrate Na4FeO4. This crystalline solid is stable when anhydrous, but extremely unstable towards disproportionation in solution. It disproportionates into sodium ferrate, sodium hydroxide and iron (III) hydroxide instantly on contact with water.
Sodium hypoferrate is synthesized in crucibles with the following reaction:
- 8 Na2O + 2 Fe2O3 + O2 → 4 Na4FeO4
This requires blowing hot oxygen or air through the crucible. If you cannot do that, you can use sodium peroxide for that:
- 8 Na2O2 + 2 Fe2O3 → 4 Na4FeO4 + 3O2
Excess oxygen will cause a side reaction that directly leads to formation of solid sodium ferrate:
- 4 Na2O2 + 2 Fe2O3 + O2 → 4 Na2FeO4
The resulting solid is a mixture of sodium hypoferrate and sodium ferrate. If you conduct this synthesis with both sodium peroxide and blowing hot oxygen, it is possible for the second reaction to dominate, resulting in a working method that can be used to synthesize solid sodium ferrate of reasonable purity.
Projects
- Oxidize organic compounds
Handling
Safety
Sodium ferrate is non-toxic. The products of its decomposition aren't toxic either. However, dry sodium ferrate should not come in contact with flammable organic compounds.
Storage
Dry sodium ferrate should be stored in a dark place, without access to air (it reacts with carbon dioxide in the air). Ideally, it should be kept under vacuum or inert gas.
Sodium ferrate solutions are very perishable and cannot be stored for any longer period of time.
Disposal
Sodium ferrate solutions can just be poured into the ground or drain. Contact with any organics causes the ferrate to be quickly reduced and decomposed.
