Ammonium bromide, with the chemical formula NH4Br, is a chemical compound composed of ammonium ions (NH4+) and bromide ions (Br-). It is a white crystalline solid that is highly soluble in water.

Ammonium bromide has several key properties and uses, including:

1. Pharmaceutical and Medicinal Uses: Ammonium bromide has been historically used in the pharmaceutical industry as a sedative and anticonvulsant. However, its use in modern medicine has declined due to the availability of safer and more effective alternatives.
2. Photography: In traditional black and white photography, ammonium bromide was used in photographic emulsions as a halide source. It played a role in controlling the sensitivity of the photographic material to light.
3. Laboratory Reagent: Ammonium bromide is used as a laboratory reagent in various chemical reactions and analyses.
4. Chemical Synthesis: It serves as a source of bromide ions in chemical synthesis processes.
5. Galvanizing and Tinning: Ammonium bromide has been used in metal surface treatment processes, such as galvanizing and tinning, to improve the adhesion of coatings.
6. Flame Retardant: Ammonium bromide has some applications as a flame retardant in certain materials and products.

While ammonium bromide has historically found uses in various applications, its significance in modern industrial and pharmaceutical settings has diminished. This is due to the availability of safer and more effective alternatives for its former uses.

As with any chemical compound, proper safety precautions should be taken when handling ammonium bromide, and its use should adhere to relevant safety guidelines and regulations.