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Crystal violet
File:Methyl Violet 10B.png
IUPAC name
4-[(4-dimethylaminophenyl)-phenyl-methyl]-N,N-dimethyl-aniline
Other names
C.I. 42555, C.I. Basic violet 3,
Andergon, Aniline violet, Axuris, Badil, Baszol Violet 57L, Brilliant Violet 58, Crystal violet, Gentiaverm, Hexamethyl-p-rosaniline chloride, Meroxylan, Meroxyl, Methylrosanilide chloride, Methyl Violet 10B, Methyl Violet 10BNS, Pyoktanin, Vianin, Viocid, and Viola Crystallina
style="background: #F8EABA; text-align: center;" colspan="2" | Identifiers
CAS number 548-62-9 YesY
PubChem 11057
MeSH Gentian+violet
style="background: #F8EABA; text-align: center;" colspan="2" | Properties
Molecular formula C25H30ClN3
Molar mass 407.979 g/mol
style="background: #F8EABA; text-align: center;" colspan="2" | Hazards
LD50 1.2 g/kg (oral, mice)

1.0 g/kg (oral, rats)[1]

 YesY (what is this?)  (verify)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Crystal violet or Gentian violet (also hexamethyl pararosaniline chloride) is a triarylmethane dye. The dye is used as a histological stain and in Gram’s method of classifying bacteria. Crystal violet has antibacterial, antifungal, and anthelmintic properties and was formerly important as a topical antiseptic. The medical use of the dye has been largely superseded by more modern drugs, although it is still listed by the World Health Organization.

The name "gentian violet" was original used for a mixture of methyl pararosaniline dyes (methyl violet) but is now often considered a synonym for crystal violet. The name refers to its colour, being like that of the petals of a gentian flower; it is not made from gentians or from violets.

Production

A number of possible routes can be used to prepare crystal violet.[2][3] The original procedure developed by Kern and Caro involved the reaction of dimethylaniline with phosgene to give 4,4'-bis(dimethylamino)benzophenone (Michler's ketone) as an intermediate.[4] This was then reacted with additional dimethylaniline in the presence of phosphorus oxychloride and hydrochloric acid.[5]

The dye can also be prepared by the condensation of formaldehyde and dimethylaniline to give a leuco dye:[2][3][6]

CH2O + 3 C6H5N(CH3)2 → CH(C6H4N(CH3)2)3 + H2O

Second, this colourless compound is oxidized to the coloured cationic form: (A typical oxidizing agent is manganese dioxide).

CH(C6H4N(CH3)2)3 + HCl + 1/2 O2 → [C(C6H4N(CH3)2)3]Cl + H2O

Dye color

When dissolved in water the dye has a blue-violet colour with an absorbance maximum at 590 nm and an extinction coefficient of 87,000 M-1cm-1.[7] The colour of the dye depends on the acidity of the solution. At a pH of 1.0 the dye is green with absorption maxima at 420 nm and 620 nm while in a strongly acidic solution (pH of -1), the dye is yellow with an absorption maximum at 420 nm.

The different colours are a result of the different charged states of the dye molecule. In the yellow form all three nitrogen atoms carry a positive charge, of which two are protonated, while the green colour corresponds to a form of the dye with two of the nitrogen atoms positively charged. At neutral pH both extra protons are lost to the solution leaving only one of the nitrogen atoms positive charged. The pKa’s for the loss of the two protons are approximately 1.15 and 1.8.[7]

In alkaline solutions, nucleophilic hydroxyl ions attack the electrophilic central carbon to produce the colourless triphenylmethanol or carbinol form of the dye. Some triphenylmethanol is also formed under very acid condition when the positive charges on the nitrogen atoms lead to an enhancement of the electrophilic character of the central carbon which allows the nucleophilic attack by water molecules. This effect produces a slight fading of the yellow colour.

Applications

Non-medical

Crystal violet is not used as a textile dye. Instead it is used to dye paper and as a component of navy blue and black inks for printing, ball-point pens and ink-jet printers. It is also used to colourize diverse products such as fertilizers, anti-freezes, and detergents.

The dye is also used as a histological stain, particularly in Gram's method for classifying bacteria.

Medical

Gentian violet has antibacterial, antifungal, and anthelmintic properties.[8] It is commonly used for:

  • Marking the skin for surgery preparation and allergy testing
  • Tinea; e.g. Athlete's foot, jock itch, and ringworm
  • Candida albicans and related infections; e.g. thrush, yeast infections
  • Mouth ulcers[9]
  • Impetigo, used primarily before the advent of antibiotics, but still useful to persons who may be allergic to penicillin, as it cleans the open sores and prevents spread of the contagion
  • Abrasion; It has also one of the best agents for "scabbing" up an abrasion or "strawberry" type of weeping wound where the flesh is abraded away. It will prevent infection in almost any wound or burn and quickly help the epithelium form a scab. It does not burn when applied and temporary skin discoloration is a minor side effect.

In forensics, gentian violet was used to develop fingerprints. Crystal violet is also used as a tissue stain in the preparation of light microscopy sections.[10]

In laboratory, solutions containing crystal violet and formalin are often used to simultaneously fix and stain cells grown in tissue culture to preserve them and make them easily visible, since most cells are colourless. It is also sometimes used as a cheap way to put identification markings on laboratory mice since many strains of lab mice are albino so the purple colour stays on their fur for several weeks.

In body piercing, gentian violet is commonly used to mark the location for placing piercings, including surface piercings.

Gentian violet was once used as antiseptic for Singaporean prisoners who received caning. The solution was applied after the procedure.

History

Synthesis

Crystal violet is one of the components of methyl violet, a dye that was first synthesized by Charles Lauth in 1861.[11] From 1866, methyl violet was manufactured by the Saint-Denis based firm of Poirrier et Chappat and marketed under the name "Violet de Paris". It was a mixture of the tetra-, penta- and hexamethylated pararosanilines.[12]

Crystal violet itself was first synthesized in 1883 by Alfred Kern (1850-1893) working in Basel at the firm of Bindschedler and Busch.[5] To optimize the difficult synthesis which used the toxic gas phosgene (carbonyl chloride), Kern entered into a collaboration with the German chemist Heinrich Caro at BASF.[4] Kern also found that by starting with diethylaniline rather than dimethylaniline he could synthesize the closely related violet dye now known as C.I. 42600 or C.I. Basic violet 4.[13]

Gentian violet

The name "gentian violet" (or Gentianaviolett in German) is thought to have been introduced by the German pharmacist George Grübler who in 1880 created a company in Leipzig that specialized in the sale of staining reagents for histology.[14][15] The gentian violet stain marketed by Grübler probably contained a mixture of methylated pararosaniline dyes.[16] The stain proved popular and in 1884 was used by Hans Christian Gram to stain bacteria. He credited Paul Ehrlich for the aniline-gentian violet mixture.[17] Grübler's gentian violet was probably very similar, if not identical, to Lauth’s methyl violet which had been used as a stain by Victor André Cornil in 1875.[18]

Although the name gentian violet continued to be used for the histological stain, the name was not used in the dye and textile industries.[19] The composition of the stain was not defined and different suppliers used different mixtures. In 1922 the Biological Stain Commission appointed a committee chaired by Harold Conn to look into the suitability of the different commercial products.[14] In his book Biological Stains Conn describes gentian violet as a "poorly defined mixture of violet rosanilins".[19]

The German ophthalmologist Jakob Stilling is credited with discovering the antiseptic properties of gentian violet.[20] He published a monograph in 1890 on the bactericidal effects of a solution that he christened "pyoktanin" which was probably a mixture of aniline dyes similar to gentian violet.[21] He set up a collaboration with E. Merck & Co. to market "Pyoktanin caeruleum" as an antiseptic.

In 1902, Drigalski and Conradi found that although crystal violet inhibited the growth of many bacteria, it has little effect on Bacillus coli (Escherichia coli) and Bacillus typhi (Salmonella typhi), which are both Gram-negative bacteria.[22] A much more detailed study of the effects of Grübler’s gentian violet on different strains of bacteria was published by John Churchman in 1912.[23] He found that most Gram-positive bacteria were sensitive to the dye while most Gram-negative bacteria were not and observed that the dye tended to act as a bacteriostatic agent rather than a bactericide.

Precautions

One study in mice demonstrated dose-related carcinogenic potential at several different organ sites[24][25]. The Food and Drug Administration in the US has determined that gentian violet has not been shown by adequate scientific data to be safe for use in animal feed. Use of gentian violet in animal feed causes the feed to be adulterated and is a violation of the Federal Food, Drug, and Cosmetic Act in the US. On June 28, 2007, the US food and Drug Administration issued an "import alert" on farm raised seafood from China because unapproved antimicrobials, including gentian violet, had been consistently found in the products. The FDA report states:

"Like MG [malachite green], CV [crystal violet] is readily absorbed into fish tissue from water exposure and is reduced metabolically by fish to the leuco moiety, leucocrystal violet (LCV). Several studies by the National Toxicology Program reported that the carcinogenic and mutagenic effects of crystal violet in rodents. It has also been linked to increased risk of human bladder cancer. The leuco form induces renal, hepatic and lung tumor in mice."[26]

Gentian violet's common side effect is the staining skin and cloth, but it can easily be washed off of skin with a solution of bleach and water. However, if used on ulcerations or open wounds it can cause tattooing. It is generally considered safe for use on children and breastfeeding mothers. It has even been applied to the mouth and lips of premature infants, and has a long history of safe use. Many have recommended it for thrush on the nipple, and La Leche League lists gentian violet as a possible alternative.[27] However, in large quantities, gentian violet may lead to ulceration of a baby's mouth and throat and is linked with mouth cancer.[28] Gentian violet has also been linked to cancer in the digestive tract of other animals[29].

Popular culture

In Catch-22, the medics are portrayed as using gentian violet on feet and gums as a panacea. This may be because of the fact that in World War I American soldiers returning after a leave were irrigated with Gentian violet to prevent sexually transmitted disease.

In Picnic at Hanging Rock, the orphan Sara recounts how she was once punished by an orphanage's matron, who 'painted my head with gentian violet'.

At Queen's Faculty of Engineering & Applied Science, students use gentian violet to dye their skin and jackets, a process known colloquially as 'purpling'.

See also

References

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Further reading

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External links

Iron/Hemosiderin
Lipids
Carbohydrates
Amyloid
Bacteria
Connective tissue
Other
Tissue stainability
cs:Genciánová violeť

ja:クリスタルバイオレット pl:Gencjana

pt:Violeta de genciana
  1. ↑ Hodge, H.C.; Indra, J.; Drobeck, H.P.; Duprey, L.P.; Tainter, M.L. (1972), Acute oral toxicity of methylrosaniline chloride, 22, pp. 1–5, doi:10.1016/0041-008X(72)90219-0 
  2. ↑ 2.0 2.1 Colour Index 3rd Edition Volume 4 (PDF), Bradford: Society of Dyers and Colourists, 1971, p. 4391 
  3. ↑ 3.0 3.1 Gessner, T.; Mayer, U. (2002), "Triarylmethane and Diarylmethane Dyes", Ullmann's Encyclopedia of Industrial Chemistry 6th Edition, Weinheim: Wiley-VCH, doi:10.1002/14356007.a27_179 
  4. ↑ 4.0 4.1 Reinhardt, C.; Travis, A.S. (2000), Heinrich Caro and the creation of modern chemical industry, Dordrecht, Netherlands: Kluwer Academic, pp. 208–209, ISBN 0792366026 
  5. ↑ 5.0 5.1 US 290856, Caro, H. & A. Kern, "Manufacture of dye-stuff", issued 1883 
    US 290891, Kern, A., "Manufacture of dye-stuff or coloring-matter", issued 1883 
    US 290892, Kern, A., "Manufacture of purple dye-stuff", issued 1883 
  6. ↑ Thetner, D. (2000), "Triphenylmethane and related dyes", Kirk-Othmer Encyclopedia of Chemical Technology, Wiley . Also available from Scribd.
  7. ↑ 7.0 7.1 Adams, E.Q.; Rosenstein, L. (1914), "The color and ionization of crystal-violet", J. Amer. Chem. Soc., 36: 1452–1473, doi:10.1021/ja02184a014 
  8. ↑ Docampo, R.; Moreno, S.N. (1990), "The metabolism and mode of action of gentian violet", Drug Metab. Rev., 22: 161–178, doi:10.3109/03602539009041083, PMID 2272286 
  9. ↑ IMCI chartbook
  10. ↑ Sheila A. Henneman and Frank S. Kohn (1975). "Methylene blue staining of tissue culture monolayers". Methods in Cell Science. 1: 103. doi:10.1007/BF01352624. 
  11. ↑ Lauth, C. (1867), "On the new aniline dye, 'Violet de Paris'", Laboratory, 1: 138–139 
  12. ↑ Gardner, W.M., ed. (1915), The British coal-tar industry : its origin, development, and decline, Philadelphia: Lippincott, p. 173 
  13. ↑ US 290893, Kern, A., "Manufacture of dye-stuff or coloring-matter", issued 1883 ; Also available from Google.
  14. ↑ 14.0 14.1 Conn, H.J. (1922), "An investigation of American gentian violets: Report of Committee on Bacteriological Technic" (PDF), J. Bacteriol., 7 (5): 529–536 
  15. ↑ Titford, M. (1993), "George Grübler and Karl Hollborn: two founders of the biological stain industry", J. Histotechnol., 16: 155–158, PMID 11615369 
  16. ↑ Titford, M. (2007), "Comparison of historic Grübler dyes with modern counterparts using thin layer chromatography", Biotech. Histochem., 82: 227–234, PMID 18074269 
  17. ↑ Clark, G.; Kasten, F.H. (1983), The history of staining (3rd ed.), Baltimore: Williams and Wilkins, pp. 95–97, ISBN 0683017055  (Earlier editions were authored by H.J. Conn)
  18. ↑ Cornil, V. (1875), "Sur la dissociation du violet de méthylaniline et sa séparation en deux couleurs sous l'influence de certains tissus normaux et pathologiques, en particulier par les tissus en dégénérescence amyloïde", Comptes Rendus de l'Académie des Sciences, 80: 1288–1291 
  19. ↑ 19.0 19.1 Conn, H.J. (1925), Biological stains: a handbook on the nature and uses of the dyes employed in the biological laboratory, Geneva, NY: Commission on Standardization of Biological Stains, pp. 68–69 
  20. ↑ Council on Pharmacy and Chemistry (1937), New and Nonofficial Remedies, Chicago: American Medical Association, pp. 210–211 
  21. ↑ Stilling, J. (1890), Anilin Farbstoffe als Antiseptica und ihre Anwendung in der Praxis, Strassbourg: Mittheilung 
  22. ↑ Drigalski, V.; Conradi, H. (1902), "Ueber ein Verfahren zum Nachweis der Typhusbacillen", Zeitschrift für Hygiene, 39 (1): 283–300, doi:10.1007/BF02140310 
  23. ↑ Churchman, J.W. (1912), "The selective bactericidal action of gentian violet", Journal of Experimental Medicine, 16 (2): 221–247, plates 21–31, doi:10.1084/jem.16.2.221 
  24. ↑ Littlefield, N.A.; Blackwell, B.N.; Hewitt, C.C.; Gaylor, D.W. (1985), "Chronic toxicity and carcinogenicity studies of gentian violet in mice.", Fundam. Appl. Toxicol., 5: 902–912, PMID 4065463 
  25. ↑ Carcinogenic Potency Database (CPDB)
  26. ↑ Questions and Answers on FDA's Import Alert on Farm-Raised Seafood From China: What evidence is there that malachite green, gentian violet and nitrofuran cause cancer?, US Food and Drug Administration, 2009, retrieved 2010-08-18 
  27. ↑ www.lalecheleague.org
  28. ↑ Drinkwater, Paul (1990). "Gentian Violet — Is It Safe?". The Australian and New Zealand Journal of Obstetrics and Gynaecology. 30: 65. doi:10.1111/j.1479-828X.1990.tb03199.x. 
  29. ↑ extoxnet.orst.edu
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