Silver nitrate is one of the inorganic compounds with AgNO3 as its chemical formula. The compound is an adaptable progenitor to various other compounds of silver, like those used in colour photography. It is more sensitive to light than other halides. The silver ions in solid silver nitrate are tri-coordinated in a trilateral planar setup.
Preparation of Silver Nitrate
Silver nitrate is usually prepared by taking a compound of silver, such as silver foil or silver bullion and reacting it with nitric acid. Once the reaction is complete, we will obtain products such as silver nitrate, water and oxides of nitrogen. The concentration of nitric acid used will determine the reaction byproducts.
- 3 Ag + 4 HNO3 (cold and diluted) → 3 AgNO3 + 2 H2O + NO
- Ag + 2 HNO3 (hot and concentrated) → AgNO3 + H2O + NO2
The reaction occurs under a fume hood to prevent the release of toxic nitrogen oxides.
Silver Nitrate Reactions
A typical reaction of silver nitrate is to suspend a copper rod in a silver nitrate solution and keep it undisturbed for a few hours. The silver nitrate reacts with copper to produce silver crystals along with a blue copper nitrate solution.
2 AgNO3 + Cu → Cu(NO3)2 + 2 Ag
When silver nitrate is heated, it decomposes.
2 AgNO3(l) → 2 Ag(s) + O2(g) + 2NO2(g)
Decomposition is qualitatively negligible lower than the melting point but proves to be appreciable around 250oC and decomposes completely at 440oC.
Many metal nitrates decompose thermally to reactive oxides, while silver oxide decomposes at a temperature lower than that of silver nitrate; hence, the decomposition of silver nitrate gives elemental silver.
Uses of Silver Nitrate
Silver nitrate is a corrosive metal that is administered either in the form of a liquid or a stick diluted with water.
Silver nitrate is diluted with water in liquid form with 0.01% to 10% concentration. This solution serves as a mild antiseptic in medical setups. A 1 to 2 per cent solution is strong enough against gonococcal bacteria that are responsible for gonorrhoea. Beginning in 1881, doctors administered the solution of silver nitrate into the eyes of babies born to mothers affected by gonorrhoea to prevent the babies from blindness due to the infection.
Silver nitrate is also used for the treatment and removal of unwanted warts. Warts are also caused by cauterising wounds and lesions to prevent bleeding and infection. The stick is moistened ideally with distilled water and kept against the wound or lesion for one or two minutes once daily.
Silver nitrate is used in laboratories, apart from its various medical applications, to test for the presence of substances like hydroxide, chlorine and iodine ions. It is consumed in manufacturing permanent fabric markers and hair dyes. A solution consisting of 2 to 3 per cent silver nitrate can slow down the blooming of cut flowers and stay fresh for longer.
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