Silver Halides - Periodic Table of Videos

A Silver Halide (or silver salt) is one of the chemical compounds that can form between the element silver and one of the halogens. In particular, bromine, chlorine, iodine and fluorine may each combine with silver to produce silver bromide (AgBr), silver chloride (AgCl), silver iodide (AgI), and three forms of silver fluoride, respectively.

As a group, they are often referred to as the silver halides, and are often given the pseudo-chemical notation AgX. Although most silver halides involve silver atoms with oxidation states of +1 (Ag⁺), silver halides in which the silver atoms have oxidation states of +2 (Ag²⁺) are known, of which silver(II) fluoride is the only known stable one.

Silver halides are light-sensitive chemicals, and are commonly used in photographic film and paper.

Silver halides, except for silver fluoride, are very insoluble in water. Silver nitrate can be used to precipitate halides; this application is useful in quantitative analysis of halides. The three main silver halide compounds have distinctive colours that can be used to quickly identify halide ions in a solution. The silver chloride compound forms a white precipitate, silver bromide a creamy coloured precipitate and silver iodide a yellow coloured precipitate.

However, close attention is necessary for other compounds in the test solution. Some compounds can considerably increase or decrease the solubility of AgX. Examples of compounds that increase the solubility include: cyanide, thiocyanate, thiosulfate, thiourea, amines, ammonia, sulfite, thioether, crown ether. Examples of compounds that reduces the solubility include many organic thiols and nitrogen compounds that do not possess solubilizing group other than mercapto group or the nitrogen site, such as mercaptooxazoles, mercaptotetrazoles, especially 1-phenyl-5-mercaptotetrazole, benzimidazoles, especially 2-mercaptobenzimidazole, benzotriazole, and these compounds further substituted by hydrophobic groups. Compounds such as thiocyanate and thiosulfate enhance solubility when they are present in a sufficiently large quantity, due to formation of highly soluble complex ions, but they also significantly depress solubility when present in a very small quantity, due to formation of sparingly soluble complex ions.