Ammonium iron(II) sulfate is widely used in analytical chemistry as a primary standard for the titration of potassium permanganate solutions. It serves as a reducing agent in redox reactions, particularly in the determination of oxidizing agents. In water treatment, it is employed to remove phosphates and other contaminants, aiding in the purification process. Additionally, it is utilized in the synthesis of other iron compounds and as a nutrient in agricultural applications to address iron deficiencies in soil. Its role in laboratory settings also extends to being a calibration substance for various instruments.