Ammonium iron(II) sulfate dodecahydrate, also known as Mohr's salt, is used as a stable source of Fe(II) ions in redox titrations. It serves as a primary standard for standardizing oxidizing titrants such as potassium permanganate (KMnO₄), potassium dichromate (K₂Cr₂O₇), or ceric sulfate in cerimetry, particularly for the determination of iron content or oxidant concentrations. The solution is valued for its resistance to aerial oxidation compared to simple ferrous sulfate, ensuring reliability in analytical procedures. The endpoint is typically indicated by the color of the titrant (e.g., pink for excess KMnO₄). Commonly employed in environmental labs for water and wastewater analysis, pharmaceutical quality control, and industrial monitoring where precise redox measurements are essential.