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Lead nitrate: structure, properties, obtaining, uses

Its chemical formula is Pb (NO 3 ) 2 . It is a white crystalline solid very soluble in water, where it forms the Pb 2+ and NO  ions . It is also known as plumbose nitrate because lead is in its lowest oxidation state.

Solid lead nitrate. Ondřej Mangl / Public domain. Source: Wikimedia Commons.

It has strongly oxidizing properties, which is why it is used in applications where this characteristic is required, such as in the preparation of various organic compounds and as a laboratory reagent.

In the past it was widely used to prepare lead-based dyes, where it also acted as a color fixer on fabrics. This application was abandoned due to lead toxicity.

However, it is a dangerous substance because it can favor the generation of fires. It is also toxic to humans, animals and plants , so it should never be disposed of in the environment.

Structure

It is an ionic compound formed by a Pb 2+ cation and two NO  anions . In the nitrate anion the oxygens are arranged symmetrically around the nitrogen and the double bond alternates with it.

Structure of Pb (NO 3 ) 2 . Edgar181 / Public domain. Source: Wikimedia Commons.
Spatial structure of Pb (NO 3 ) 2 . Gray = lead; blue = nitrogen; red = oxygen. Claudio Pistilli / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0). Source: Wikimedia Commons.

Lead in this compound has the following electronic configuration:

[Xe] 4 14 5 10 6 2 6 0 , where it is observed that it has lost the 2 electrons of the last shell.

Nomenclature

  • Lead nitrate
  • Lead (II) nitrate
  • Plumbous nitrate
  • Lead dinitrate

Properties

Physical state

White or colorless crystalline solid. Cubic crystals.

Molecular weight

331 g / mol

Melting point

470 ° C. According to some sources it decomposes at this temperature.

Density

4.53 g / cm 3

Solubility

Very soluble in water: 59.7 g / 100 mL of water at 25 ° C. Slightly soluble in ethanol. Insoluble in concentrated nitric acid (HNO 3 ).

pH

An aqueous solution with 20% Pb (NO 3 ) 2 has a pH of 3.0-4.0.

Chemical properties

It is an oxidizing agent. Reacts violently with combustible and reducing materials.

It is not combustible but it can accelerate the burning of materials that are. If heated to decomposition, it emits toxic nitrogen oxide gases:

When dissolved in water, it ionizes:

Pb (NO 3 ) 2 + H 2 O → Pb 2+ + 2 NO 

Obtaining

It can be prepared by reacting metallic lead, lead monoxide (PbO) or lead carbonate PbCO 3 with nitric acid. It is advisable to use excess acid to avoid the formation of basic nitrates.

PbO + 2 HNO 3 (concentrated) → Pb (NO 3 ) 2 ↓ + H 2 O

Applications

In organic synthesis

Its oxidizing capacity has application in the preparation of various compounds.

It has been used to synthesize calixarenes, which are organic compounds whose molecule has the shape of a basket that allows it to house other substances depending on the use that will be given to it.

It is used to obtain isothiocyanates (R-NCS) starting from amines (R-NH 2 ).

It is used on an industrial scale to prepare benzaldehyde by oxidizing benzyl chloride. It also serves as a catalyst for the esterification of organic compounds, for example in the production of polyesters.

In chemical analysis

It is used as a reagent in the determination of aluminum and lead in minerals and rocks.

In the coloring of textile fibers

Some chromium dyes require the use of Pb (NO 3 ) 2 to obtain them. For example, to dye cotton yellow, the cotton is coated with lead nitrate and treated with sodium sulfate to produce lead sulfate.

Then a dilute sodium dichromate solution is applied to form lead chromate (PbCrO 4 ) which is a yellow pigment.

Some time ago, fabrics were colored yellow with pigments whose starting point was Pb (NO 3 ) 2 . Currently this is not done due to lead toxicity. Author: 3D Animation Production Company. Source: Pixabay.

However, today lead pigments have been discontinued due to their toxicity.

It also acts as a mordant to fix the dyes during the coloring or printing of other types of fiber.

In veterinary medina

It was formerly used as a caustic agent in the treatment of cankers or gangrenes in horses.

In the metal industry

Lead nitrate is used in the electrolytic refining of lead, as an agent to promote flotation in the removal of titanium from certain clays, it makes it possible to recover precious metals from cyanide solutions and is used in the electrodeposition of PbO 2 in nickel anodes.

In solar cells

It has been used in the form of an aqueous solution to make solar cells based on perovskite, a mineral of titanium oxide.

The synthesized material is an organometallic perovskite or lead iodide perovskite that has attracted the attention of researchers, as it has a high light absorption capacity and a great diffusion length of charge carriers.

These characteristics make it an excellent candidate for photovoltaic devices, that is, that convert light into electrical current.

Photomicrograph of the structure of a lead halide perovskite taken with a fluorescence microscope. Furasova / CC BY (https://creativecommons.org/licenses/by/4.0). Source: Wikimedia Commons.

Other apps

(PbNO 3 ) 2 has also been used:

  • in the manufacture of matches, certain explosives and pyrotechnic materials,
  • in photography as a sensitizing agent to coat paper in photothermography,
  • in the textile industry to improve rayon and stabilize nylon,
  • in the elimination of rodents.
Lead nitrate has been used to make fireworks or pyrotechnic material. Author: Free-Photos. Source: Pixabay.

Risks

Fire and explosion

Although it is not a combustible compound, if it is exposed to fire or heat it can explode, generating toxic nitrogen oxides.

As it is a strongly oxidizing agent, there is a danger of a fire being generated if it comes into contact with organic materials.

To health

Produces irritation to the eyes, respiratory and digestive tract. It is toxic by inhalation and ingestion. The most common symptoms of intoxication by this compound are gastrointestinal disorders, colic, constipation and weakness that can turn into paralysis of some muscles, among others.

Ingestion can also cause pain, cramps, depression, coma, and death.

For the natural environment

It is toxic to aquatic and terrestrial organisms, in addition its damages are persistent and it bioaccumulates in living beings, therefore it is considered a dangerous pollutant and should not be disposed of into the environment.

If it is accidentally spilled in water, it must be neutralized with calcium oxide (CaO), calcium carbonate (CaCO 3 ) or sodium bicarbonate (NaHCO 3 ).

It has been confirmed to be carcinogenic to animals and possibly humans.

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