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Mercury(II) chloride (or mercury bichloride, mercury dichloride), historically also known as sulema or corrosive sublimate, is the inorganic
chemical compound A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
of mercury and
chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
with the
formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwe ...
HgCl2. It is white crystalline
solid Solid is one of the four fundamental states of matter (the others being liquid, gas, and plasma). The molecules in a solid are closely packed together and contain the least amount of kinetic energy. A solid is characterized by structur ...
and is a laboratory
reagent In chemistry, a reagent ( ) or analytical reagent is a substance or compound added to a system to cause a chemical reaction, or test if one occurs. The terms ''reactant'' and ''reagent'' are often used interchangeably, but reactant specifies a ...
and a molecular compound that is very toxic to humans. Once used as a treatment for
syphilis Syphilis () is a sexually transmitted infection caused by the bacterium '' Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, a ...
, it is no longer used for medicinal purposes because of
mercury toxicity Mercury poisoning is a type of metal poisoning due to exposure to mercury. Symptoms depend upon the type, dose, method, and duration of exposure. They may include muscle weakness, poor coordination, numbness in the hands and feet, skin rashes ...
and the availability of superior treatments.


Synthesis

Mercuric chloride is obtained by the action of
chlorine Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine i ...
on mercury or on mercury(I) chloride. It can also be produced by the addition of
hydrochloric acid Hydrochloric acid, also known as muriatic acid, is an aqueous solution of hydrogen chloride. It is a colorless solution with a distinctive pungent smell. It is classified as a strong acid. It is a component of the gastric acid in the dige ...
to a hot, concentrated solution of mercury(I) compounds such as the
nitrate Nitrate is a polyatomic ion with the chemical formula . Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are soluble in water. An example of an insolu ...
: :Hg2(NO3)2 + 4 HCl → 2 HgCl2 + 2 H2O + 2 NO2 Heating a mixture of solid
mercury(II) sulfate Mercury(II) sulfate, commonly called mercuric sulfate, is the chemical compound Hg S O4. It is an odorless solid that forms white granules or crystalline powder. In water, it separates into an insoluble sulfate with a yellow color and sulfuric a ...
and
sodium chloride Sodium chloride , commonly known as salt (although sea salt also contains other chemical salts), is an ionic compound with the chemical formula NaCl, representing a 1:1 ratio of sodium and chloride ions. With molar masses of 22.99 and 35. ...
also affords volatile HgCl2, which can be separated by sublimation. Process for synthesis of Mercuric chloride first appeared in Abu Bakr al-Razi's ''De aluminibus et salibus.''


Properties

Mercuric chloride exists not as a salt composed of discrete ions, but rather is composed of linear triatomic molecules, hence its tendency to sublime. In the crystal, each mercury atom is bonded to two chloride
ligand In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's elect ...
s with Hg—Cl distance of 2.38 Å; six more chlorides are more distant at 3.38 Å. Its solubility increases from 6% at to 36% in . In the presence of chloride ions, it dissolves to give the tetrahedral
coordination complex A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as '' ligands'' or complexing agents. M ...
gCl4sup>2−.


Applications

The main application of mercuric chloride is as a
catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
for the conversion of
acetylene Acetylene ( systematic name: ethyne) is the chemical compound with the formula and structure . It is a hydrocarbon and the simplest alkyne. This colorless gas is widely used as a fuel and a chemical building block. It is unstable in its pure ...
to
vinyl chloride Vinyl chloride is an organochloride with the formula H2C=CHCl. It is also called vinyl chloride monomer (VCM) or chloroethene. This colorless compound is an important industrial chemical chiefly used to produce the polymer polyvinyl chloride (PVC ...
, the precursor to polyvinyl chloride: :C2H2 + HCl → CH2=CHCl For this application, the mercuric chloride is supported on carbon in concentrations of about 5 weight percent. This technology has been eclipsed by the thermal cracking of
1,2-dichloroethane The chemical compound 1,2-dichloroethane, commonly known as ethylene dichloride (EDC), is a chlorinated hydrocarbon. It is a colourless liquid with a chloroform-like odour. The most common use of 1,2-dichloroethane is in the production of vin ...
. Other significant applications of mercuric chloride include its use as a depolarizer in batteries and as a reagent in
organic synthesis Organic synthesis is a special branch of chemical synthesis and is concerned with the intentional construction of organic compounds. Organic molecules are often more complex than inorganic compounds, and their synthesis has developed into one o ...
and
analytical chemistry Analytical chemistry studies and uses instruments and methods to separate, identify, and quantify matter. In practice, separation, identification or quantification may constitute the entire analysis or be combined with another method. Separati ...
(see below). It is being used in plant tissue culture for surface sterilisation of explants such as leaf or stem nodes.


As a chemical reagent

Mercuric chloride is occasionally used to form an
amalgam Amalgam most commonly refers to: * Amalgam (chemistry), mercury alloy * Amalgam (dentistry), material of silver tooth fillings ** Bonded amalgam, used in dentistry Amalgam may also refer to: * Amalgam Comics, a publisher * Amalgam Digital, an in ...
with metals, such as
aluminium Aluminium (aluminum in American and Canadian English) is a chemical element with the symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately one third that of steel. It ha ...
. Upon treatment with an aqueous solution of mercuric chloride, aluminium strips quickly become covered by a thin layer of the amalgam. Normally, aluminium is protected by a thin layer of oxide, thus making it inert. Once amalgamated, aluminium can undergo a variety of reactions. For example, upon removal of the oxide layer, the exposed aluminium will immediately react with water generating Al(OH)3 and hydrogen gas.
Halocarbon Halocarbon compounds are chemicals in which one or more carbon atoms are linked by covalent bonds with one or more halogen atoms (fluorine, chlorine, bromine or iodine – ) resulting in the formation of organofluorine compounds, organochlor ...
s react with amalgamated aluminium in the
Barbier reaction The Barbier reaction is an organometallic reaction between an alkyl halide (chloride, bromide, iodide), a carbonyl group and a metal. The reaction can be performed using magnesium, aluminium, zinc, indium, tin, samarium, barium or their salts. ...
. These alkylaluminium compounds are nucleophilic and can be used in a similar fashion to the Grignard reagent. Amalgamated aluminium is also used as a
reducing agent In chemistry, a reducing agent (also known as a reductant, reducer, or electron donor) is a chemical species that "donates" an electron to an (called the , , , or ). Examples of substances that are commonly reducing agents include the Earth met ...
in organic synthesis. Zinc is also commonly amalgamated using mercuric chloride. Mercuric chloride is used to remove dithiane groups attached to a carbonyl in an umpolung reaction. This reaction exploits the high affinity of Hg2+ for anionic sulfur ligands. Mercuric chloride may be used as a stabilising agent for chemicals and analytical samples. Care must be taken to ensure that detected mercuric chloride does not eclipse the signals of other components in the sample, such as is possible in
gas chromatography Gas chromatography (GC) is a common type of chromatography used in analytical chemistry for separating and analyzing compounds that can be vaporized without decomposition. Typical uses of GC include testing the purity of a particular substanc ...
.


Historical use in photography

Mercury(II) chloride was used as a photographic intensifier to produce positive pictures in the
collodion process The collodion process is an early photographic process. The collodion process, mostly synonymous with the "collodion wet plate process", requires the photographic material to be coated, sensitized, exposed, and developed within the span of about ...
of the 1800s. When applied to a negative, the mercury(II) chloride whitens and thickens the image, thereby increasing the opacity of the shadows and creating the illusion of a positive image.


Historical use in preservation

For the preservation of anthropological and biological specimens during the late 19th and early 20th centuries, objects were dipped in or were painted with a "mercuric solution". This was done to prevent the specimens' destruction by moths, mites and mold. Objects in drawers were protected by scattering crystalline mercuric chloride over them. It finds minor use in tanning, and wood was preserved by kyanizing (soaking in mercuric chloride). Mercuric chloride was one of the three chemicals used for railroad tie wood treatment between 1830 and 1856 in Europe and the United States. Limited railroad ties were treated in the United States until there were concerns over lumber shortages in the 1890s. The process was generally abandoned because mercuric chloride was water-soluble and not effective for the long term, as well as being highly poisonous. Furthermore, alternative treatment processes, such as
copper sulfate Copper sulfate may refer to: * Copper(II) sulfate, CuSO4, a common compound used as a fungicide and herbicide * Copper(I) sulfate Copper(I) sulfate, also known as cuprous sulfate, is an inorganic compound with the chemical formula Cu2 SO4. It ...
,
zinc chloride Zinc chloride is the name of inorganic chemical compounds with the formula ZnCl2 and its hydrates. Zinc chlorides, of which nine crystalline forms are known, are colorless or white, and are highly soluble in water. This salt is hygroscopic ...
, and ultimately
creosote Creosote is a category of carbonaceous chemicals formed by the distillation of various tars and pyrolysis of plant-derived material, such as wood or fossil fuel. They are typically used as preservatives or antiseptics. Some creosote types were ...
; were found to be less toxic. Limited kyanizing was used for some railroad ties in the 1890s and early 1900s.


Historic use in medicine

Mercuric chloride was a common over-the-counter disinfectant in the early twentieth century, recommended for everything from fighting measles germs to protecting fur coats and exterminating red ants. A New York physician, Carlin Philips, wrote in 1913 that "it is one of our most popular and effective household antiseptics", but so corrosive and poisonous that it should only be available by prescription. A group of physicians in Chicago made the same demand later the same month. The product frequently caused accidental poisonings and was used as a suicide method. It was used to disinfect wounds by Arab physicians in the Middle Ages. It continued to be used by Arab physicians into the twentieth century, until modern medicine deemed it unsafe for use.
Syphilis Syphilis () is a sexually transmitted infection caused by the bacterium '' Treponema pallidum'' subspecies ''pallidum''. The signs and symptoms of syphilis vary depending in which of the four stages it presents (primary, secondary, latent, a ...
was frequently treated with mercuric chloride before the advent of
antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and preventio ...
. It was inhaled, ingested, injected, and applied topically. Both mercuric-chloride treatment for syphilis and poisoning during the course of treatment were so common that the latter's symptoms were often confused with those of syphilis. This use of "salts of white mercury" is referred to in the
English English usually refers to: * English language * English people English may also refer to: Peoples, culture, and language * ''English'', an adjective for something of, from, or related to England ** English national ...
-language
folk song Folk music is a music genre that includes traditional folk music and the contemporary genre that evolved from the former during the 20th-century folk revival. Some types of folk music may be called world music. Traditional folk music has ...
"
The Unfortunate Rake "The Unfortunate Lad", also known as "The Unfortunate Rake", is a traditional folk ballad (), which through the folk process has evolved into a large number of variants. Synopsis In nineteenth-century broadside versions, the narrator meets a com ...
".
Yaws Yaws is a tropical infection of the skin, bones, and joints caused by the spirochete bacterium ''Treponema pallidum pertenue''. The disease begins with a round, hard swelling of the skin, in diameter. The center may break open and form an ulc ...
was treated with mercuric chloride (labeled as Corrosive Sublimate) before the advent of
antibiotics An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and preventio ...
. It was applied topically to alleviate ulcerative symptoms. Evidence of this is found in Jack London's book ''The Cruise of the Snark'' in the chapter entitled "The Amateur M.D."


Historic use in crime and accidental poisonings

*In volume V of
Alexandre Dumas Alexandre Dumas (, ; ; born Dumas Davy de la Pailleterie (), 24 July 1802 – 5 December 1870), also known as Alexandre Dumas père (where '' '' is French for 'father', to distinguish him from his son Alexandre Dumas fils), was a French writer ...
' ''Celebrated Crimes'', he recounts the history of
Antoine François Desrues Antoine François Desrues (1744–1777) was a French poisoner. Desrues was born at Chartres, of humble parents. He went to Paris to seek his fortune, and started in business as a grocer. He was known as a man of great piety and devotion, and his b ...
, who killed a noblewoman, Madame de Lamotte, with "corrosive sublimate". *In 1906, in New York, Richard Tilghman died after mistaking bichloride of mercury tablets for
lithium citrate Lithium citrate (Li3C6H5O7) is a chemical compound of lithium and citrate that is used as a mood stabilizer in psychiatric treatment of manic states and bipolar disorder. There is extensive pharmacology of lithium, the active component of this ...
tablets. *In one highly publicized case in 1920, "mercury bichloride" was reported to have caused the death of 25-year-old American silent-film star Olive Thomas. While vacationing in France and staying at the Hôtel Ritz in Paris, she accidentally (or perhaps intentionally) ingested the compound, which had been prescribed to her husband Jack Pickford in liquid topical form to treat his "chronic syphilis". Thomas died five days later. *Mercuric chloride was used by Madge Oberholtzer to commit suicide after she was kidnapped, raped, and tortured by
Ku Klux Klan The Ku Klux Klan (), commonly shortened to the KKK or the Klan, is an American white supremacist, right-wing terrorist, and hate group whose primary targets are African Americans, Jews, Latinos, Asian Americans, Native Americans, and Cat ...
leader D.C. Stephenson. Oberholtzer died from a combination of mercury poisoning and staph infection, the latter caused by Stephenson biting her during the assault.Daniel O. Linder, "D.C. Stephenson"
Testimony, ''Famous Trials'', hosted at University of Missouri Law School, Kansas City
*Ana María Cires, a young wife of Uruguayan writer
Horacio Quiroga Horacio Silvestre Quiroga Forteza (31 December 1878 – 19 February 1937) was a Uruguayan playwright, poet, and short story writer. He wrote stories which, in their jungle settings, used the supernatural and the bizarre to show the struggle of m ...
, committed suicide by poisoning herself. After a violent fight with the writer, she ingested a fatal dose of "sublimado", or Mercury(II) chloride. She endured terrible agony for eight days before dying on December 14, 1915. * Ruth L. Truffant's death was called a suicide after she succumbed to the effects of Bichloride of mercury poisoning on 26 April 1914.


Toxicity

Mercury dichloride is highly toxic compound, both acutely and as a cumulative poison. Its toxicity is due not just to its mercury content but also to its corrosive properties, which can cause serious internal damage, including ulcers to the stomach, mouth, and throat, and corrosive damage to the intestines. Mercuric chloride also tends to accumulate in the kidneys, causing severe corrosive damage which can lead to acute kidney failure. However, mercuric chloride, like all inorganic mercury salts, does not cross the
blood–brain barrier The blood–brain barrier (BBB) is a highly selective semipermeable border of endothelial cells that prevents solutes in the circulating blood from ''non-selectively'' crossing into the extracellular fluid of the central nervous system where ne ...
as readily as organic mercury, although it is known to be a cumulative poison. Common side effects of acute mercuric chloride poisoning include burning sensations in the mouth and throat, stomach pain, abdominal discomfort, lethargy, vomiting of blood, corrosive bronchitis, severe irritation to the gastrointestinal tract, and kidney failure. Chronic exposure can lead to symptoms more common with mercury poisoning, such as insomnia, delayed reflexes, excessive salivation, bleeding gums, fatigue, tremors, and dental problems. Acute exposure to large amounts of mercuric chloride can cause death in as little as 24 hours, usually due to acute kidney failure or damage to the gastrointestinal tract. In other cases, victims of acute exposure have taken up to two weeks to die."Mercuric chloride"
in ''ToxNet: Hazardous Substances'' data bank. National Institutes of Health (2002, October 31). Retrieved on April 17, 2005. See also the corresponding entry in ''ToxNet'''s successor, ''PubChem''.


References


External links

* Agency for toxic substances and disease registry. (2001, May 25)
Toxicological profile for Mercury
Retrieved on April 17, 2005. * US National Institutes of Health. Retrieved 19 July 2022.
Archived
20 July 2022. * Young, R.(2004, October 6)
Toxicity summary for mercury
The risk assessment information system. Retrieved on April 17, 2005.

* ttp://www.atsdr.cdc.gov/toxprofiles/tp46.html ATSDR - Toxicological Profile: Mercury*
National Pollutant Inventory - Mercury and compounds Fact Sheet
* - includes excerpts from research reports. {{DEFAULTSORT:Mercury(Ii) Chloride Mercury(II) compounds Chlorides Metal halides Alchemical substances Photographic chemicals Pulmonary agents