Silver Nitrate

Properties and Structure of Silver Nitrate and Its Applications

Chemical Compounds are of two types. They are classified as organic and inorganic compounds. Silver Nitrate is an inorganic compound. Its chemical formula is AgNO3. When Silver (Ag) reacts with Nitric Acid (HNO3), the chemical reaction results in the formation of Silver Nitrate. The Symbol Ag used for Silver originates from the Latin word “Argentum”. This reaction is done under very controlled conditions because this results in the emission of toxic fumes of nitrogen oxides.
Silver Nitrate is also called as Lunar Caustic. It kills microorganisms and will also react with compounds in human flesh. That is why it has been used in the medical industry The word "Caustic" means which can corrode. Improper use of Lunar caustic on the human body can cause severe damage. The alchemists believed that the chemical silver was always associated with the moon. The Latin word for Moon is Luna, so it was named Lunar Caustic.

The chemical reaction is represented as given below:

3 Ag + 4 HNO3  → 3 AgNO3 + 2 H2O + NO

In this case, the nitric acid is generally cold and diluted. When silver reacts with hot and concentrated nitric acid, it emits nitrogen dioxide.

Properties and Structure:

Silver Nitrate is a salt, which is colorless or of a white crystalline form. When this is exposed to light or any organic material, this becomes black in color. Silver Nitrate when heated decomposes and forms, Silver, Nitrogen dioxide and Oxygen.

The molar mass of Silver nitrate is 169.87 gm/mole. It has a melting point of 212∘C. It is highly soluble in water and also soluble in Ethanol and Acetone.

Applications of Silver Nitrate:

Silver nitrate is broadly used in two fields – Medical and industrial applications. Silver nitrate is a precursor of many other silver compounds that are used. Hence, one of the use of Silver Nitrate is in the preparation of other Silver compounds. Silver nitrate is a very caustic chemical. This is used in the preparation of other silver salts. Colloidal compounds of silver, that are used in medicine are also prepared using silver nitrate. In photographic emulsions, Silver halides are used, and these, in turn, are prepared with Silver nitrate. This is also used in labs for volumetric analysis to determine, halides, thiocyanates etc:

Some of the medical applications of Silver Nitrate are:

  • 1. Eye drops for children: In the year 1881, it was first used in the manufacture of eye drops. This was used to treat or prevent any hereditary infections of eye transmitted to the child from the mother. However, these days it is not used as a preventive remedy. It has been proven that bacteria, Gonococcal Bacteria which is a principal cause of eye infections are eliminated by this chemical.

  • 2. Some people have moles on their hands or bodies. Silver nitrate is used to cauterize and remove such moles.

  • 3. In the field of dentistry, it is used to heal ulcers in the mouth.

  • However, though it is known to be used in treatment to cure some problems as mentioned above, Silver Nitrate should not be consumed or used without doctor’s advice or consultation.

    Some of the Industrial Applications of Silver Nitrate are

  • 1. Electroplating: Such plating work is done on jewelry and watches to give a sophisticated finish and look. Silver Nitrate is used when Silver must be coated on Nickel.

  • 2. We all use mirrors in our day to day life. Mirrors reflect whatever is in front of it. In order to create such a surface that reflects, Silver Nitrate is used. A coating of Silver Nitrate is used on glass, which then makes the conversion of plain glass to mirror possible.

  • 3. It is also used in the manufacturing of many coloring agents like dyes and inks. Some people use hair dyes in which silver nitrate is added. In the textile industry, they use markers to mark on the fabric. Such markers also use Silver Nitrate. There are inks which can never be removed, they are called indelible inks, which also use this chemical.

  • 4. Explosives are used to break rocks to lay roads etc: The manufacture of such explosives also uses silver nitrate and also includes other salts of silver like silver acetylide, silver azide etc:

  • 5. Today's world is using digital photography. Earlier, photographs were taken with films which were washed and processed (called as Developing of photos). In the process of making photographic films, a small number of Silver halides (eg: silver bromide, silver chloride) was used. When stuck with light while taking photographs, there would be a decomposition to elemental silver, which would leave an image. This could then be developed into a photo by using other chemicals.

  • 6. We all see different ceramic pottery in different colors. Silver Nitrate is used to add such colors in the ceramic works.

  • 7. Pesticide products that have Silver Nitrate as an active ingredient are used in the cut flower industry. These are used to prevent early or premature withering of plants and dropping of buds and flowers. Cut stems make ethylene, which helps to hasten the process of fruit ripening and aging of plants. When these stems are placed in a very dilute solution of Silver Nitrate then this process is delayed.

  • Thus, Silver Nitrate has its uses in various areas. However, it is important to be very careful in using this chemical as it can cause damage if improperly handled.

    Impact of light on Silver Nitrate:

    When Silver Nitrate is stored in labs, it is always advised to store them in dark bottles. There is a specific reason for this. Silver Nitrate is very sensitive to light. This means, that the chemical will react when exposed to light. So, when this is left exposed to sunlight or any bright light, it will start to hydrolyze. This will result in the formation of black or brown colored silver oxide and nitric acid. If this is stored in dark bottles, and kept away from contact with direct light, this reaction can be minimized and hence can be stored for a longer duration.

    Bulk Storage and Handling of Silver Nitrate:

    Silver Nitrate is an oxidizing agent, which means it will readily give out oxygen. Oxygen supports combustion or fire. Hence, while storing these chemicals, care should be taken to ensure that they are stored away from any chemical that is combustible or flammable. The reason being, that in case of a fire, the Silver Nitrate decomposes, can add to the fire by providing oxygen. Hence care should be taken to store them separately.

    Adverse Health effects of Silver Nitrate:

    Based on data available as of now following effects are caused by Silver Nitrate;

    These are categorized as acute effects.

    Silver Nitrate is a caustic chemical. Hence this will cause irritation. When it is absorbed in the skin over a long period of time it causes a greyish discoloring of tissues. This phenomenon is called argyria.

    If inhaled, this will cause irritation and damage to mucous membranes.

    If Silver Nitrate is taken in by mouth, it can have dangerous effects and sometimes cause death also. It can cause vomiting, bloody diarrhea, dizziness and convulsions also.

    Some of the Chronic effects due to long term exposure to Silver Nitrate are:

    It can cause, general depression, headache, and loss of mental capability. In some cases of people who have been exposed to Silver Nitrate, Cancer also has been observed.

    When somebody comes into contact with Silver Nitrate, the contact portion must be washed with large quantities of fresh water. They should be immediately provided with medical attention.

    Silver Nitrate is also highly toxic to fish and other aquatic life forms. Hence the disposal of this chemical also should be done in complete conformance with local laws and regulations.

    Silver Nitrate is also used in Criminal Investigations. Generally, in crime scene fingerprints are found. One type of fingerprint, called the Latent print is not visible to the human eye. Such prints are left when sweat or natural body oils make contact with other surfaces. Investigators use a method called Latent Print development to solve or identify such prints. In such processes of developing the latent print, Silver Nitrate is used. In our skin secretions, there is some element of chlorides. Silver nitrate reacts with these secretions and forms silver chloride. These turn to grey color when exposed to UV light. Thus, this chemical helps in the field of criminal investigations also.