5. SILVER NITRATE
Silver nitrate is an inorganic compound with chemical
formula AgNO3
This compound is a versatile precursor to many
other silver compounds, such as those used
in photography. It is far less sensitive to light than
the halides. It was once called lunar caustic because
silver was called luna by the ancient alchemists, who
believed that silver was associated with the moon.
6. PREPARATION
Silver nitrate is made in large quantities by dissolving silver in
nitric acid. It crystallizes in transparent plates that melt at 212 °C
(414 °F). The solubility at 20 °C (68 °F) is 222 grams per 100
grams of water. It is moderately soluble in methyl and ethyl
alcohols and to a lesser extent in various other organic solvents.
When heated to about 320° C (608° F), silver nitrate loses
oxygen and forms silver nitrite. At a red heat, silver is formed.
7. CONT.…
Silver nitrate can be prepared by reacting silver, such as
a silver bullion or silver foil, with nitric acid, resulting in
silver nitrate, water, and oxides of nitrogen. Reaction
byproducts depend upon the concentration of nitric acid
used.
3 Ag + 4 HNO3 (cold and diluted) → 3 AgNO3 + 2 H2O +
NO
Ag + 2 HNO3 (hot and concentrated) → AgNO3 + H2O +
NO2
This is performed under a fume hood because of toxic
nitrogen oxide(s) evolved during the reaction
8. PROPERTIES
Silver salts have antiseptic properties.
In 1881 Credé introduced the use of dilute solutions of AgNO3
in newborn babies' eyes at birth to prevent contraction of
gonorrhea from the mother, which could cause blindness.
Fused silver nitrate, shaped into sticks, was traditionally called
"lunar caustic". It is used as a cauterizing agent, for example to
remove granulation tissue around a stoma.
9. CONT.…….
Silver nitrate is also used by some podiatrists
to kill cells located in the nail bed.
General Sir James Abbott noted in his journals that in
India in 1827 it was infused by a British surgeon into
wounds in his arm resulting from the bite of a mad dog
to cauterize the wounds and prevent the onset of
rabies.
10. CONT.…..
Silver nitrate is also used to cauterize superficial blood
vessels in the nose to help prevent nose bleeds.
The Canadian physician C. A. Douglas Ringrose
researched the use of silver nitrate for sterilization
procedures on women, believing that silver nitrate
could be used to block and corrode the fallopian
tubes. The technique was ineffective.
11. CONT..
Scientists in India are reporting successful laboratory
tests of a new and potentially safer alternative to silver-
based gels applied to the skin of burn patients to treat
infections. With names like silver sulfadiazine and silver
nitrate, these germ-fighters save lives and speed healing.
