Iron(II) oxalate

Ferrous oxalate (also called iron(II) oxalate) is a chemical with the formula  where x can be 0 or 2. These compounds are yellow. Like many metal oxalates, they form long chains called polymers, which makes them hard to dissolve in water.

 Structure 
Like other iron oxalates, ferrous oxalates have iron atoms in an octahedral shape. The dihydrate form, , is a coordination polymer. It has chains where oxalate groups link the iron atoms, and each iron is also attached to two water molecules.
400x400px|Ball-and-stick model of a chain in the crystal structure of iron(II) oxalate dihydrate

 Reactions 
When heated to 120 °C, the compound with water loses its water. The dry ferrous oxalate breaks down near 190 °C. When it breaks down, it makes a mix of iron oxides and iron metal that can catch fire easily. It also releases carbon dioxide, carbon monoxide, and water.

Ferrous oxalates are starting materials used to make iron phosphates. Iron phosphates are important for batteries.

 Natural occurrence 
As of 2020, anhydrous iron(II) oxalate is not found as a mineral. But the form with water, called dihydrate, is known as humboldtine. There is a related mineral called stepanovite, which has a special mix of elements and water, and is a rare natural ferrioxalate.

 References 

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Category:Iron compounds