Ammonium thiosulfate, identified by its CAS number 7783-18-8, is a fascinating chemical compound whose properties underpin its utility in various critical applications, most notably in photography. Understanding its inherent characteristics, such as its chemical properties and stability, is essential for maximizing its effectiveness and ensuring safe handling. One of the defining attributes of ammonium thiosulfate is its physical appearance: typically presenting as colorless or light yellow crystals. It carries a characteristic ammoniacal odor, a subtle yet distinctive feature. Chemically, its molecular formula is (NH4)2S2O3, with a molecular weight of 148.20500. Its stability is generally good, though it is noted as being hygroscopic, meaning it readily absorbs moisture from the air. This characteristic necessitates proper storage in tightly closed containers to maintain its integrity. In terms of solubility, ammonium thiosulfate dissolves readily in water, a property vital for its use in aqueous solutions for photographic fixing and other industrial processes. It exhibits only slight solubility in acetone and is practically insoluble in ethanol and diethyl ether. This selective solubility plays a role in its effectiveness and separation in various chemical environments. When discussing ammonium thiosulfate photographic fixer, its rapid action is a key benefit. Unlike its sodium counterpart, ammonium thiosulfate's ability to complex with silver ions is more pronounced, leading to faster fixation times. This efficiency is a significant advantage in modern photographic workflows, especially when dealing with contemporary film emulsions. Beyond photography, the ammonium thiosulfate industrial applications are diverse. Its function as a reducing agent, its role in metal cleaning, and its inclusion in electroplating solutions underscore its chemical versatility. The ammonium thiosulfate chemical properties that enable these functions are critical for manufacturers and researchers alike. When considering the compound, its CAS number (7783-18-8) is the universal identifier, ensuring that the correct substance is being sourced and utilized. The detailed information regarding its melting point (180°C, with decomposition) and density (1.679 g/mL at 25°C) provides further insight into its behavior under different conditions. In essence, ammonium thiosulfate is a compound with a well-defined set of ammonium thiosulfate chemical properties that make it invaluable. Whether for achieving optimal photographic results or for its role in industrial chemistry, a thorough understanding of its nature is paramount.