Iron(II) carbonate

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iron(II) carbonate

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Template:Longitem	FeCO3
Molar mass	115.854 g/mol
Appearance	white powder or crystals
Density	3.9 g/cm3
Melting point	Template:Chembox CalcTemperatures
Template:Longitem	3.13Template:E
Template:Longitem	+11,300·10−6 cm3/mol
Template:Longitem	Hexagonal scalenohedral / Trigonal (32/m) Space group: R 3c, a = 4.6916 Å, c = 15.3796 Å
Template:Longitem	6
Template:Longitem	iron(II) sulfate
Template:Longitem	copper(II) carbonate, zinc carbonate

Iron(II) carbonate, or ferrous carbonate, is a chemical compound with formula Template:Chem/link, that occurs naturally as the mineral siderite. At ordinary ambient temperatures, it is a green-brown ionic solid consisting of iron(II) cations Template:Chem/link and carbonate anions Template:Chem/link. The compound crystallizes in the same motif as calcium carbonate. In this motif, the carbonate dianion is nearly planar. Its three oxygen atoms each bind to two Fe(II) centers, such that the Fe has an octahedral coordination geometry.

Preparation

Ferrous carbonate can be prepared by reacting solution of the two ions, such as iron(II) chloride and sodium carbonate:

Template:Chem/link + Template:Chem/link → Template:Chem/link + 2Template:Chem/link

Ferrous carbonate can be prepared also from solutions of an iron(II) salt, such as iron(II) perchlorate, with sodium bicarbonate, releasing carbon dioxide:

Template:Chem/link(Template:Chem/link)₂ + 2Template:Chem/link → Template:Chem/link + 2Template:Chem/link + Template:Chem/link + Template:Chem/link

Sel and others used this reaction (but with Template:Chem/link instead of Template:Chem/link(Template:Chem/link)₂) at 0.2 M to prepare amorphous Template:Chem/link.

Care must be taken to exclude oxygen Template:Chem/link from the solutions, because the Template:Chem/link ion is easily oxidized to Template:Chem/link, especially at pH above 6.0.

Ferrous carbonate also forms directly on steel or iron surfaces exposed to solutions of carbon dioxide, forming an "iron carbonate" scale:

Template:Chem/link + Template:Chem/link + Template:Chem/link → Template:Chem/link + Template:Chem/link

Properties

The dependency of the solubility in water with temperature was determined by Wei Sun and others to be

$\log K_{{s}{p}}=-59.3498-0.041377T-2.1963/T+24.5724\log T+2.518\sqrt{I}-0.657I,$

where T is the absolute temperature in kelvins, and I is the ionic strength of the liquid.

Iron carbonate decomposes at about .

Uses

Ferrous carbonate has been used as an iron dietary supplement to treat anemia. It is noted to have very poor bioavailability in cats and dogs.

Toxicity

Ferrous carbonate is slightly toxic; the probable oral lethal dose is between 0.5 and 5 g/kg (between 35 and 350 g for a 70 kg person).

Iron(III) carbonate

Unlike iron(II) carbonate, iron(III) carbonate has not been isolated. Attempts to produce iron(III) carbonate by the reaction of aqueous ferric ions and carbonate ions result in the production of iron(III) oxide with the release of carbon dioxide or bicarbonate.