... .dry blue-green cryastal cargo. 3.mainly used in industry water treatment,agriculture fertilizer, Name of Specification/Index IndexFeSO4.7H2O98% min.Fe19 ... ,ink iron oxide red and indigo-blue, as mordant, tanning, water purification, preservative of wood and disinfectant etc. In agriculture, it ... bag of 25kgs.net each. ferrous sulphate (heptahydrate used for water treatment)