what is ferrous sulfate used for

{"cid":"91221745","title":"Ferrous Sulfate Monohydrate Powder Composition and Uses Storage","imgUrl":"https:\/\/img.chinax.com\/nimg\/47\/da\/dab1e6f4d8b74934d5f3a72bc661-200x200-1.jpg","attrs":{"Brand Name":"JD","Model Number":"JD-FSMFG-99","Minimum Order Quantity":"20TONS","Delivery Time":"5 DAYS","Certification":"ISO9001","Place of Origin":"CHINA","Payment Terms":"T\/T","Supply Ability":"1000TONS","Packaging Details":"25KG PP BAG","Synonyms:":"FERROUS SULFATE MONOHYDRATE;sulfuric acid iron(2+) salt monohydrate;Iron sulfate monohydrate;Iron(2+) sulfate monohydrate;Ferrous Sulphate Monohydrate (FeSO4)","CAS Number:":"17375-41-6","Molecular Formula:":"FeSO4.1H2O","Colour":"white-yellow monoclinic crystals","Water Solubility\u00a0":"soluble H2O","Density":"3.000","The loading qty":"25TONS\/container","HS CODE":"2834210000"}}

{"cid":"91224289","title":"Polymeric Ferric Sulfate PFS Liquid - High Efficiency Flocculant with Broad pH Adaptability and Low Residual Iron Ions for Water Treatment","imgUrl":"https:\/\/img.chinax.com\/nimg\/38\/8a\/4fbee4ef14d89044acb559208cac-200x200-1.jpg","attrs":{"Price":"Please contact customer service","Brand Name":"SiChun HongJian","Model Number":"Polyferric sulfate","Minimum Order Quantity":"10Tons","Delivery Time":"About six weeks","Place of Origin":"China","Payment Terms":"T\/T,L\/C,D\/A,D\/P,Western Union,MoneyGram","Supply Ability":"100,000 tons per year","Packaging Details":"Bagged","chemical formula":"[Fe2(OH)n(SO4)3-n\/2]m","CAS No":"35139-28-7","Appearance and Characteristics":"Yellow or reddish brown amorphous powder or granular solid"}}