Used as a photosensitive agent in blueprint paper and photographic processes, especially in early photographic techniques like cyanotype printing. Acts as a precursor in the synthesis of iron-based nanoparticles and catalysts. Employed in metal etching and surface treatment due to its ability to complex with metals. Also utilized in some dyeing and printing processes in the textile industry as a mordant to fix colors. Shows application in analytical chemistry for the determination of certain metal ions through precipitation or redox reactions.