Mercury(II) chloride

Mercury(II) chloride
Names
IUPAC names
Mercury(II) chloride
Mercury dichloride
Other names
Mercuric chloride
Corrosive sublimate
TL-898
Identifiers
CAS Number
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.028.454 Edit this at Wikidata
EC Number
  • 231-299-8
KEGG
PubChem CID
RTECS number
  • OV9100000
UNII
UN number 1624
InChI
  • InChI=1S/2ClH.Hg/h2*1H;/q;;+2/p-2 ☒N
SMILES
  • Cl[Hg]Cl
Properties
Chemical formula
 HgCl2
Molar mass 271.52 g/mol
Appearance colorless or white solid
Odor odorless
Density 5.43 g/cm3
Melting point 276 °C (529 °F; 549 K)
Boiling point 304 °C (579 °F; 577 K)
Solubility in water
 3.6 g/100 mL (0 °C)
7.4 g/100 mL (20 °C)
48 g/100 mL (100 °C)
Solubility 4 g/100 mL (ether)
soluble in alcohol, acetone, ethyl acetate
slightly soluble in benzene, CS2, pyridine
Acidity (pKa) 3.2 (0.2M solution)
Magnetic susceptibility (χ)
 −82.0·10−6 cm3/mol
Refractive index (nD)
 1.859
Structure
Crystal structure
 orthogonal
Coordination geometry
 linear
Molecular shape
 linear
Dipole moment
 zero
Thermochemistry
Std molar
entropy (So298)
 144 J·mol−1·K−1[1]
Std enthalpy of
formation (ΔfH⦵298)
 −230 kJ·mol−1[1]
Gibbs free energy (ΔfG˚)
 -178.7 kJ/mol
Pharmacology
D08AK03 (WHO)
Hazards
GHS labelling:
Pictograms
Signal word
 Danger
Hazard statements
 H300, H314, H341, H361f, H372, H410
Precautionary statements
 P201, P202, P260, P264, P270, P273, P280, P281, P301+P310, P301+P330+P331, P303+P361+P353, P304+P340, P305+P351+P338, P308+P313, P310, P314, P321, P330, P363, P391, P405, P501
NFPA 704 (fire diamond)
4
0
1
Flash point Non-flammable
Safety data sheet (SDS) ICSC 0979
Related compounds
Other anions
 Mercury(II) fluoride
Mercury(II) bromide
Mercury(II) iodide
Other cations
 Zinc chloride
Cadmium chloride
Mercury(I) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Mercury(II) chloride or mercuric chloride (historically also known as corrosive sublimate)[2] is the chemical compound of mercury and chlorine with the formula HgCl2. It is white crystalline solid and is a laboratory reagent and a molecular compound that is very toxic to humans. Once used as a treatment for syphilis, it is no longer used for medicinal purposes because of mercury toxicity and the availability of superior treatments.

Synthesis

Mercuric chloride is obtained by the action of chlorine on mercury or on mercury(I) chloride. It can also be produced by the addition of hydrochloric acid to a hot, concentrated solution of mercury(I) compounds such as the nitrate:[2]

Hg2(NO3)2 + 4 HCl → 2 HgCl2 + 2 H2O + 2 NO2

Heating a mixture of solid mercury(II) sulfate and sodium chloride also affords volatile HgCl2, which can be separated by sublimation.[2]

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 ligands with Hg—Cl distance of 2.38 Å; six more chlorides are more distant at 3.38 Å.[3]

Its solubility increases from 6% at 20 °C (68 °F) to 36% in 100 °C (212 °F). In the presence of chloride ions, it dissolves to give the tetrahedral coordination complex [HgCl4]2−.

Applications

The main application of mercuric chloride is as a catalyst for the conversion of acetylene to vinyl chloride, the precursor to polyvinylchloride:

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. Other significant applications of mercuric chloride include its use as a depolarizer in batteries and as a reagent in organic synthesis and analytical chemistry (see below).[4] 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 with metals, such as aluminium.[5] 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. Halocarbons react with amalgamated aluminium in the Barbier reaction. 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 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.[6]

Historical use in photography

Mercury(II) chloride was used as a photographic intensifier to produce positive pictures in the collodion process 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.[7]

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.[8] It finds minor use in tanning, and wood was preserved by kyanizing (soaking in mercuric chloride).[9] 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.[10] 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, zinc chloride, and ultimately creosote; were found to be less toxic. Limited kyanizing was used for some railroad ties in the 1890s and early 1900s.[11]

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[12] to protecting fur coats.[13] A New York doctor, 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.[14] A group of doctors in Chicago made the same demand later the same month. The product frequently caused accidental poisonings and was used as a suicide method.[15]

It was used to disinfect wounds by Arab physicians in the Middle Ages.[16] It continued to be used by Arab doctors into the twentieth century, until modern medicine deemed it unsafe for use.

Syphilis was frequently treated with mercuric chloride before the advent of antibiotics. 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-language folk song "The Unfortunate Rake".[17]

Yaws was treated with mercuric chloride (labeled as Corrosive Sublimate) before the advent of antibiotics. 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' Celebrated Crimes, he recounts the history of Antoine François Desrues, who killed a noblewoman, Madame de Lamotte, with "corrosive sublimate".[18]
  • In 1906, in New York, Richard Tilghman died after mistaking bichloride of mercury tablets for lithium citrate tablets.[19]
  • 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.[20][21]
  • Mercuric chloride was used by Madge Oberholtzer to commit suicide after she was kidnapped, raped, and tortured by Ku Klux Klan 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.[22]
  • Ana María Cires, a young wife of Uruguayan writer Horacio Quiroga, 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.[23]

Toxicity

Mercuric chloride is extremely toxic, 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 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.[24][25]

References

  1. 1 2 Zumdahl, Steven S. (2009). Chemical Principles 6th Ed. Houghton Mifflin Company. p. A22. ISBN 978-0-618-94690-7.
  2. 1 2 3 Chisholm, Hugh, ed. (1911). "Corrosive Sublimate" . Encyclopædia Britannica. Vol. 7 (11th ed.). Cambridge University Press. p. 197.
  3. ↑ Wells, A.F. (1984) Structural Inorganic Chemistry, Oxford: Clarendon Press. ISBN 0-19-855370-6.
  4. ↑ Matthias Simon, Peter Jönk, Gabriele Wühl-Couturier, Stefan Halbach "Mercury, Mercury Alloys, and Mercury Compounds" in Ullmann's Encyclopedia of Industrial Chemistry 2006: Wiley-VCH, Weinheim. doi:10.1002/14356007.a16_269.pub2
  5. ↑ Deng, James; Wang, Yu-Pu; Danheiser, Rick L. (2015). "Synthesis of 4,4-Dimethoxybut-1-yne". Organic Syntheses. 92: 13–25. doi:10.15227/orgsyn.092.0013.
  6. ↑ Foreman, W. T.; Zaugg, S. D.; Faires, L. M.; Werner, M. G.; Leiker, T. J.; Rogerson, P. F. (1992). "Analytical interferences of mercuric chloride preservative in environmental water samples: Determination of organic compounds isolated by continuous liquid-liquid extraction or closed-loop stripping". Environmental Science & Technology. 26 (7): 1307. Bibcode:1992EnST...26.1307F. doi:10.1021/es00031a004.
  7. ↑ Towler, J. (1864). Stereographic negatives and landscape photography. Chapter 28. In: The silver sunbeam: a practical and theoretical textbook of sun drawing and photographic printing. Retrieved on April 13, 2005.
  8. ↑ Goldberg, Lisa (1996). "A History of Pest Control Measures in the Anthropology Collections, National Museum of Natural History, Smithsonian Institution". JAIC. 35 (1): 23–43. Retrieved April 17, 2005.
  9. ↑ Freeman, M.H. Shupe, T.F. Vlosky, R.P. Barnes, H.M. (2003). Past, present and future of the wood preservation industry Archived 2005-05-03 at the Wayback Machine. Forest Products Journal. 53(10) 8–15. Retrieved on April 17, 2005.
  10. ↑ Pg. 19-75 "Date Nails and Railroad Tie Preservation" (3 vol.; 560 p.), published in 1999 by the Archeology and Forensics Laboratory, University of Indianapolis; Jeffrey A. Oaks
  11. ↑ Oaks, Jeffrey A. "History of Railroad Tie Preservation" (PDF). p. 20-30; p. 64, Table I. Archived from the original (PDF) on 2011-07-18. Retrieved 2009-01-14.
  12. ↑ "Measles Kills Many Children". The Star and Sentinel. Gettysburg, PA. 1908-01-29. Retrieved 2021-09-25.
  13. ↑ "Untitled snippet". The Day Book. Chicago, IL. 1914-05-05. Retrieved 2021-09-25.
  14. ↑ Philips, M.D., Carlin (1913-06-15). "To Keep Deadly Bichloride of Mercury from Family Medicine Shelves". The Times Dispatch. Richmond, VA. Retrieved 2021-09-25.
  15. ↑ "Want Sale of Bichloride of Mercury Restricted". The Day Book. Chicago, IL. 1913-06-23. Retrieved 2021-09-25.
  16. ↑ Maillard, Adam P. Fraise, Peter A. Lambert, Jean-Yves (2007). Principles and Practice of Disinfection, Preservation and Sterilization. Oxford: John Wiley & Sons. p. 4. ISBN 978-0470755068.
  17. ↑ Pimple, K.D. Pedroni, J.A. Berdon, V. (2002, July 09). Syphilis in history Archived 2008-04-30 at the Wayback Machine. Poynter Center for the Study of Ethics and American Institutions at Indiana University-Bloomington. Retrieved on April 20, 2008.
  18. ↑ Dumas, Alexandre (1895). Celebrated Crimes Volume V: The Cenci. Murat. Derues. G. Barrie & sons. p. 250. Retrieved 30 June 2015 – via Google Books.
  19. ↑ "The times and democrat. [volume] (Orangeburg, S.C.) 1881-current, June 28, 1906, Image 1". 28 June 1906.
  20. ↑ "Bichloride of Mercury Killed Olive Thomas". The Toronto World. September 15, 1920. p. 6. Retrieved August 27, 2018.
  21. ↑ Foster, Charles (2000). Stardust and Shadows: Canadians in Early Hollywood, page 257. Toronto, Canada: Dundurn Press, 2000. ISBN 978-1550023480.
  22. ↑ Daniel O. Linder, "D.C. Stephenson", Testimony, Famous Trials, hosted at University of Missouri Law School, Kansas City
  23. ↑ Brignol, José (1939). Vida y Obra de Horacio Quiroga. Montevido: La Bolsa de los Libros. pp. 211–213.
  24. ↑ "Mercury(II)_chloride".
  25. ↑ "Toxnet Has Moved".
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