Iron(II) carbonate


Iron carbonate, or ferrous carbonate, is a chemical compound with formula, that occurs naturally as the mineral siderite. At ordinary ambient temperatures, it is a green-brown ionic solid consisting of iron(II) cations and carbonate anions. 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 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:
Ferrous carbonate can be prepared also from solutions of an iron salt, such as iron(II) perchlorate, with sodium bicarbonate, releasing carbon dioxide:
Sel and others used this reaction at 0.2 M to prepare amorphous.
Care must be taken to exclude oxygen from the solutions, because the ion is easily oxidized to, 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:

Properties

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

Iron(III) carbonate

Unlike iron carbonate, iron carbonate is rarely encountered. Attempts to produce iron 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. It is instead produced by the heating of iron oxide at 2300 °C under 33 GPa of carbon dioxide. Iron carbonate is unstable at atmospheric pressure, decomposing back into iron oxide and carbon dioxide.