The molecular formula of ferrous sulfate is FeSO4.7H2O, which is a by-product produced in the production of rare metal products by sulfuric acid method. The appearance of the product is sky blue or green monoclinic crystal, or crystalline powder, with relative density of 1.8987, melting point of 64 ℃, soluble in water, glycerin, almost insoluble in ethanol; odorless, salty, astringent and irritating. Ferrous sulfate is mainly used as flocculant, which has good flocculation effect and decolorization ability. It also has the functions of removing heavy metal ions, oil, phosphorus, and sterilization. It is especially widely used in paper decolorization and dyeing wastewater decolorization.

1. Sewage treatment

It can be used as flocculant, reducing agent and precipitant to remove phosphate from urban and industrial wastewater to prevent eutrophication.

2. Medicinal

Ferrous sulfate is used in the treatment of iron deficiency anemia, and it is also used to add iron in food. Long term excessive use may cause abdominal pain, nausea and other side effects. In medicine, it is used as local astringent and blood tonic. The iron contained in it is the raw material for the synthesis of red blood cells in vivo. It can be used for the chronic blood loss caused by hysteromyoma.

3. Colorant

a. Ferrous sulfate is used in the production of iron tannate ink and other inks. The mordant of wood dyeing also contains ferrous sulfate.

b. Ferrous sulfate can be used to dye concrete yellow rust.

c. The wood was silvered with ferrous sulfate.

4. Agriculture

Regulating soil pH, promoting the formation of chlorophyll (also known as iron fertilizer), as the iron nutrition of microorganisms in the biochemical system, improving the activity of microorganisms in the system, preventing the yellowing of flowers and trees caused by iron deficiency, is an indispensable element for acid loving flowers and trees, especially for iron trees. In agriculture, it can also be used as a pesticide to control wheat smut, apple and pear scab and fruit tree canker; it can also be used as a fertilizer to remove the moss and lichen from the trunk.

5. Analytical chemistry

Ferrous sulfate can be used as a chromatographic reagent.