Silver nitrate (AgNO3) is an inorganic and caustic chemical compound that has a variety of different uses. ReAgent sells a range of silver nitrate products in its online shop, so what is it exactly?
Physically, silver nitrate appears as a white, odourless and crystalline solid. Chemically, its structure is made up of a silver cation (Ag+) and a nitrate anion (NO3–).
Silver nitrate can be characterised by a few properties. It is:
- Water soluble
- Insensitive to light
- An oxidising agent
- Toxic and corrosive
Although it is relatively stable under light and heat, silver nitrate can decompose when heated to high temperatures. If heated above 320°C, it loses oxygen and forms silver nitrite (AgNO2), which is much less soluble. If it reaches a red heat, it forms metallic silver.
Heating this compound releases toxic nitrogen dioxide gas. Therefore, it is important to always use a fume cupboard.
How Do You Make Silver Nitrate?
Silver nitrate is made by dissolving elemental silver in nitric acid. The by-products of this reaction depend on the strength of nitric acid used, but they usually include water and oxides of nitrogen. These can be toxic, which is another reason why a fume cupboard should always be used when handling this compound.
Silver nitrate was discovered in the 13th century by Albertus Magnus, a German Catholic friar and bishop. Also known as doctor universalis, Magnus documented that silver could be dissolved by nitric acid. Magnus also recorded that lunar caustic had the ability to darken areas of skin, which is a key identifier of silver nitrate.
The product was named lunar caustic by ancient alchemists because, at the time, silver was closely associated with the moon. Silver was also called luna because of this association.
What Are the Uses of Silver Nitrate?
Silver nitrate is commonly used to make and prepare a range of silver compounds, including silver halides and silver oxide. This is because its nitrate ion is easily replaced by other groups, making it quite a reactive compound.
Therefore, it is very useful as a precursor to many silver derivatives that are used in varying industries. The two major uses of silver nitrate are in photography and medicine.
Photographic film is coated with an emulsion that contains gelatin and microscopic silver halide crystals. These are very light-sensitive, and are made by treating AgNO3 with halide salts of sodium or potassium.
When exposed to light, the silver halides absorb it and turn black. The reason they do this is because they are decomposing into metallic silver. This chemical reaction darkens areas of the film and creates an image.
Silver nitrate is commonly used in the medical industry for its antiseptic properties. It is especially used to treat warts, where it behaves as a cauterising agent.
Doctors, dentists and podiatrists alike use AgNO3 for these properties. However, when used in the medical industry, silver nitrate is found in extremely low concentrations. It is important to note that even though it is used in this way, it is toxic and should not be consumed.
The Silver Tree experiment is a reaction that uses AgNO3 and a copper wire to create a crystal-like structure. When a copper wire is introduced into a solution of silver nitrate, a redox reaction occurs. Elemental silver is formed, and begins to accumulate around the copper wire. Meanwhile, the solution turns its signature blue colour because of the production of copper nitrate. The outcome is a structure that looks like a silver tree suspended underwater.
Silver nitrate is used for a variety of applications in a range of industries:
- Explosives: when silver nitrate in nitric acid is added to ethanol, silver fulminate is produced. This is a highly explosive silver salt that is extremely sensitive
- Silver Staining: AgNO3 is used in silver staining, which is primarily used in histology to selectively alter the appearance of a target in microscopy
- Halide Abstraction: because AgNO3 can help to prepare insoluble silver halides, it is often used in inorganic chemistry to abstract halides
- Mirrors: when a solution of silver nitrate (sometimes mixed with ammonia and sodium hydroxide) is poured onto glass, it immediately turns reflective. This used to be the preferred way to produce mirrors
Silver Nitrate Hazards
Despite its many uses and applications, silver nitrate is still a corrosive and toxic substance. It is important to always handle this substance with care, ensuring that you wear eye protection and use personal protective equipment (PPE).
If consumed, it can cause vomiting, diarrhoea, violent abdominal pains and even gastroenteritis. As well as this, it takes as little as 1 gram of silver in the body to cause argyria, a condition which causes the skin and internal organs to turn a blue-grey colour.
Silver nitrate is also classified as a skin irritant. While brief skin exposure may result in dark, even black stains, long-term exposure could result in severe burns.
Why Does Silver Nitrate Turn Skin Black?
Silver nitrate on the skin behaves similarly to the microscopic silver halides in photographic film. When it comes into contact with skin, the silver nitrate will eventually decompose into metallic silver.
This decomposition is what causes the black colour; silver particles absorb light and appear black. Even though this is generally harmless, it can be difficult to remove once the stain has turned completely black.
Here at ReAgent, we stock silver nitrate products in a variety of pack sizes and solutions. We also have our Material Safety Data Sheets (MSDS) available for you to consult. Shop online today, or speak to a member of our Technical Support team to find out what we can do for you.