Preparation of Silver Nitrate
Silver nitrate is usually prepared by taking a compound of silver such as silver foil or silver bullion and react 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 the 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 form diluted with water.
Silver nitrate is diluted with water in the 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 is responsible for gonorrhoea. Beginning in 1881, doctors administered the solution of silver nitrate into the eyes of a baby 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 cauterizing wounds and lesions to prevent bleeding and infection. The stick is moistened ideally with distilled water and kept against the war, wound or lesion for a specific time period of one or two minutes daily once.
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.