Ferrous chloride tetrahydrate was prepared using ferrous sulfate heptahydrate, ferric oxide red and circulating hydrochloric acid in

The present invention belongs to the titanium dioxide industry, hydrometallurgy and inorganic industrial chemical, especially relates to a ferrous chloride was prepared using the titanium dioxide industry by-product ferrous sulfate heptahydrate, red iron oxide and sulfuric acid process. Firstly, the present invention is the production of titanium dioxide by-product ferrous sulfate heptahydrate use of the common ion effect in concentrated hydrochloric acid prepared by crystallization of ferrous chloride tetrahydrate, and then calcined red iron oxide was prepared. The filtrate was separated from the remaining hydrochloric acid was evaporated, the remaining cooling was separated by filtration to recover ferrous sulfate heptahydrate sulfate. HCl and calcining evaporation can be recycled. The method of the present invention can be prepared cleaned into sulfite heptahydrate ferrous chloride, red iron oxide and iron concentration of about 60% sulfuric acid. The present invention, both to reduce environmental pollution, but also reduce the cost of production of titanium dioxide.