Ammonium hexacyanoferrate(II) is widely used in analytical chemistry as a reagent for detecting the presence of metal ions, particularly iron and copper. It forms characteristic colored complexes with these metals, aiding in their identification and quantification. In the photography industry, it serves as a component in cyanotype printing, where it reacts with light to produce blueprints. Additionally, it is employed in the production of pigments and dyes, contributing to the vibrant colors in various materials. In water treatment, it acts as a coagulant to remove impurities and heavy metals from wastewater. Its role in the synthesis of other coordination compounds is also significant in research and industrial applications.