What Is Silver Hydroxide?
Silver hydroxide, represented by the chemical formula AgOH, is a hydroxide compound of silver.
Silver (Ag) alone has a low ionization tendency, and it does not reduce the hydrogen ion H+ or dissolve in hydrochloric acid or dilute sulfuric acid. It is soluble only in highly oxidizing acids such as dilute nitric acid, concentrated nitric acid, and hot concentrated sulfuric acid.
It is obtained as a white precipitate by adding an alkaline solution like sodium hydroxide or ammonia water to an aqueous solution containing the silver (I) ion, Ag+, such as silver sulfate Ag2SO4 or silver nitrate AgNO3, and neutralizing the solution to approximately pH 8.5 or higher.
However, silver hydroxide is very thermally unstable, so it quickly decomposes and dehydrates to silver(I) oxide. Typically, hydrogen is produced when metals dissolve in acids, but this is not the case with silver.
In the presence of dilute or concentrated nitric acid, nitric oxide (NO) or nitrogen dioxide (NO2) is produced. Also, if the acid is hot concentrated sulfuric acid, sulfur dioxide SO2 is produced.
Uses of Silver Hydroxide
Silver hydroxide decomposes quickly to silver oxide Ag2O. When the solution containing that precipitate is made basic using excess ammonia, the silver amine complex, [Ag(NH3)2]+, is formed and dissolved.
When a compound with a formyl group, like aldehyde, is added to the solution and heated, silver ions are reduced and precipitate. This reaction is known as the silver mirror reaction because the deposited silver becomes uniform like a mirror.
Since the first half of the 19th century, it has been used in various industrial fields as a major silver plating method for surface plating of Dewar containers and for creating mirrors.