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Lead acetate: structure, properties, obtaining, uses

It is also known as “lead sugar” because it has a sweet taste. However, it is a very poisonous substance. It is a crystalline solid very soluble in water. It can easily react with hydrogen sulfide (H 2 S) generating brown lead sulfide (PbS), which is used in the detection of this toxic gas in industrial processes.

Solid lead (II) acetate. Dormroomchemist at English Wikipedia / CC BY (https://creativecommons.org/licenses/by/3.0). Source: Wikimedia Commons.

In ancient times it was obtained with relative ease, so it had uses that are currently completely prohibited due to the toxicity of this compound.

Lead acetate dust must not be dispersed in the environment, as it forms explosive mixtures with oxygen. In addition, it is a carcinogenic compound for animals and humans.

Structure

Lead (II) acetate has the structure shown in the figure below:

Lead (II) acetate molecular structure. Michał Sobkowski / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0). Source: Wikimedia Commons.

Nomenclature

  • Lead (II) acetate
  • Lead diacetate
  • Lead ethanoate
  • Plumb acetate
  • Lead sugar
  • Salt Saturn

Properties

Physical state

Colorless to white crystalline solid.

Molecular weight

325 g / mol

Melting point

280 ºC

Boiling point

It does not boil. It decomposes when heated.

Density

3.25 g / cm 3

Solubility

Very soluble in water: 44.3 g / 100 mL at 20 ° C. Insoluble in alcohol.

pH

A 5% aqueous solution has a pH of 5.5-6.5.

Chemical properties

When Pb (OCOCH 3 ) 2 dissolves in water, one part is ionized as follows:

Pb (OCOCH 3 ) 2 → Pb 2+ + 2 CH 3 COO 

However, part of the molecules does not ionize and remains in the form:

CH 3 COO-Pb-OCOCH 3 .

When the Pb 2+ ion  enters solution, it is partially hydrolyzed in water, generating the Pb 4 (OH) 4+ species .

Aqueous solutions of Pb (II) acetate dissolve lead oxide (PbO).

Reacts with hydrogen sulfide (H 2 S) to form a brown solid of lead sulfide (PbS).

Pb (OCOCH 3 ) 2 + H 2 S → PbS + 2 CH 3 COOH

Adding an aqueous solution of ammonia (NH 3 ) to a solution of lead acetate forms a precipitate or white solid of basic acetate.

Other properties

It emits an odor similar to vinegar. It has a sweet taste. Its most common commercial form is Pb (CH 3 COO) 2 • 3H 2 O trihydrate .

Lead Acetate Trihydrate. Leiem / CC BY-SA (https://creativecommons.org/licenses/by-sa/4.0). Source: Wikimedia Commons.

Obtaining

It can be prepared by dissolving lead (II) oxide or carbonate in concentrated acetic acid. Small thin metal lead plates can also be used.

PbO + 2 CH 3 COOH → (CH 3 COO) 2 Pb + H 2 O

Ancient uses

In medicine

It was used in dilute solution to apply it as poultices and washes in inflammations caused by poison ivy and as an astringent in lotions. Also to treat diarrhea.

It was used as an astringent and sedative lotion in the treatment of superficial inflammations and bruises.

In cosmetics

It was made in ancient Roman times. Some women applied it to their face to appear pale, which was not just a fad, but a question of social status.

A fair complexion indicated that the woman did not belong to the working class, but to the highest levels of Roman society. And this happened despite the fact that the doctors of the time, such as Pliny the Elder, knew about some of its harmful effects.

As a beverage sweetener

Due to its sweet taste, it was used in ancient times as a substitute for sugar, especially in wine and to sweeten and preserve fruits.

In various applications

Some of these uses still apply, but the literature consulted is not clear about it:

  • In chromium pigments, as a component in colorants for adhesives, in drying organic soaps for paints, varnishes and inks, as a water repellent, in anti-fouling paints.
  • In the process of obtaining gold using cyanides, to coat metals with lead.
  • As a mordant in cotton dyes, component of fixing baths for sunlight printing paper.
  • To treat awnings and outdoor furniture to prevent the removal of agents that protect against mold and deterioration from rain or washing.

Current uses

In the detection of H 2 S

In certain industrial processes it is used to detect the toxic H 2 S in gaseous streams by means of a test paper in which it serves as an indicator. The detection limit is 5 ppm (parts per million).

Lead (II) acetate makes it possible to detect H 2 S in industrial gases so that said toxic gas is not released into the atmosphere . Author: Leestilltaolcom. Source: Pixabay.

In recent tests it has been possible to incorporate nanofibers together with a polymer, resulting in a novel detection material that allows revealing the presence of 400 ppb (parts per billion) of H 2 S even at 90% humidity.

The high potential of this nanomaterial as a colorimetric sensor makes it applicable to the detection of H 2 S in the breath of people suffering from halitosis, whose range is below 1 ppm.

The new nanofibers containing Pb (CH 3 COO) 2 can detect very small amounts of H 2 S in breath. Author: Natalia Ovcharenko. Source: Pixabay.

In obtaining other compounds

It enables the preparation of other lead compounds such as carbonate and chromate, lead salts of high molecular weight fatty acids and antioxidants for gums.

For external use

According to some sources consulted, this compound is still used in hair dyes whose application indications warn that it should not be used on other parts of the body other than the scalp.

It is also part of analgesic products for external use and skin protectors.

However, in both cases there is not enough evidence to establish the degree of safety of these products, so in countries such as Canada and the state of California in the USA, their use in all types of cosmetics or for application has been prohibited. on the skin.

Risks

For security

It is not combustible, but if it is dispersed in the environment in the form of fine particles, it can generate explosive mixtures with air.

It should be stored away from oxidizing compounds, strong acids, and chemically active metals, and in areas without drains or access to sewers that lead to sewage.

To health

It can irritate the eyes, respiratory and digestive tracts, causing headache, nausea, vomiting, colic, muscle weakness, cramps, seizures, paralysis, dizziness, loss of consciousness, coma, and even death.

Lead acetate is absorbed about 1.5 times faster than other lead compounds.

Lead Acetate negatively affects children’s brains. Author: Pete Linforth. Source: Pixabay.

At very low blood concentrations in children it can cause hyperactivity or neurobehavioral disability, as it generates effects on the nervous system . It can also cause anemia and kidney damage .

In the case of animals it has been sufficiently proven that it is toxic for reproduction, carcinogenic and teratogenic. It is estimated that it affects humans in the same way.

For the environment

It is considered a dangerous substance for the environment, as it is a toxic pollutant. It is very harmful to aquatic organisms. Special attention must be paid to birds, mammals, soil contamination and water quality.

Bioaccumulation of this compound can occur in plants and animals. International ecological institutions strongly advise against allowing it to enter the environment because it is persistent.

Historical case of poisoning

One of the events studied has been that of the President of the United States Andrew Jackson (1767-1845), who was subjected to a treatment with “lead sugar”, which at that time was a traditional remedy with various purposes.

In 1999, measurements were carried out on two hair samples obtained during the president’s life and it was found that lead levels were very high in both samples, which is compatible with the symptoms of plumbism that he suffered.

Andrew Jackson was intoxicated by lead acetate-based remedies. Author: Gordon Johnson. Source: Pixabay.

Both his letters and his biographer describe that he presented symptoms such as nausea, abdominal cramps and paralytic rheumatism, among others. But after a while Jackson gave up the lead acetate treatment, so his health improved.

Therefore, it is estimated that his death was probably not due to lead poisoning.

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