Iron(II) chloride
Iron chloride, also known as ferrous chloride, is the chemical compound
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 of formula FeCl2. It is a paramagnetic solid with a high melting point, and is usually obtained as an off-white solid. FeCl2 crystallizes from water as the greenish tetrahydrate
Water of crystallization
In crystallography, water of crystallization or water of hydration or crystallization water is water that occurs in crystals. Water of crystallization is necessary for the maintenance of crystalline properties, but capable of being removed by sufficient heat...

, which is the form that is most commonly encountered in commerce and the laboratory. There is also a dihydrate. The compound is also soluble in water; aqueous solutions of FeCl2 are yellow.
Hydrated forms of ferrous chloride are generated by treatment of wastes from steel production with hydrochloric acid
Hydrochloric acid
Hydrochloric acid is a solution of hydrogen chloride in water, that is a highly corrosive, strong mineral acid with many industrial uses. It is found naturally in gastric acid....

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