Methyl violet

Template:Short description Methyl violet is a family of organic compounds that are mainly used as dyes. Depending on the number of attached methyl groups, the color of the dye can be altered. Its main use is as a purple dye for textiles and to give deep violet colors in paint and ink. It is also used as a hydration indicator for silica gel. Methyl violet 10B is also known as crystal violet (and many other names) and has medical uses.<ref name="pyoctanin_Gorgas" />

Structure

The term methyl violet encompasses three compounds that differ in the number of methyl groups attached to the amine functional group. Methyl violets are mixtures of tetramethyl (2B), pentamethyl (6B) and hexamethyl (10B) pararosanilins.<ref>Template:Cite journal</ref>

They are all soluble in water, ethanol, diethylene glycol and dipropylene glycol.

Name	Methyl violet 2B	Methyl violet 6B	Methyl violet 10B (Crystal violet)
Structure	File:Methyl Violet 2B.svg	File:Methyl Violet 6B.svg	Methyl violet 10B Methyl violet 10B
Formula (salt)	C23H26ClN3	C24H28ClN3	C25H30ClN3
CAS no	84215-49-6	8004-87-3	548-62-9
C.I.	42536	42535	42555
ChemSpider ID	21164086	170606	10588
PubChem ID	91997555	164877	11057
Formula (cation)	C23H26N3+	C24H28N3+	C25H30N3+
ChemSpider ID		2006225	3349, 9080056, 10354393
PubChem ID		2724053	3468

Methyl violet 2B

Methyl violet 2B (IUPAC name: 4,4′-((4-Iminocyclohexa-2,5-dien-1-ylidene)methylene)bis(N,N-dimethylaniline) monohydrochloride) is a green powder which is soluble in water and ethanol but not in xylene. It appears yellow in solution of low pH (approximately 0.15) and changes to violet with pH increasing toward 3.2.<ref name=b1>Template:Cite book</ref>

Methyl violet 10B

Template:Main Methyl violet 10B has six methyl groups. It is known in medicine as Gentian violet (or crystal violet or pyoctanin(e)<ref name="pyoctanin_Gorgas">Template:Cite journal</ref>) and is the active ingredient in a Gram stain, used to classify bacteria. It is used as a pH indicator, with a range between 0 and 1.6. The protonated form (found in acidic conditions) is yellow, turning blue-violet above pH levels of 1.6.<ref>Kristallviolett – ein pH-Indikator Template:Webarchive</ref>

Methyl violet 10B inhibits the growth of many Gram positive bacteria, except streptococci.Template:Citation needed When used in conjunction with nalidixic acid (which destroys gram-negative bacteria), it can be used to isolate the streptococci bacteria for the diagnosis of an infection.Template:Citation needed

Degradation

Methyl violet is a mutagen and mitotic poison, therefore concerns exist regarding the ecological impact of the release of methyl violet into the environment. Methyl violet has been used in vast quantities for textile and paper dyeing, and 15% of such dyes produced worldwide are released to environment in wastewater. Numerous methods have been developed to treat methyl violet pollution. The three most prominent are chemical bleaching, biodegradation, and photodegradation.

Chemical bleaching

Chemical bleaching is achieved by oxidation or reduction. Oxidation can destroy the dye completely, e.g. through the use of sodium hypochlorite (NaClO, common bleach) or hydrogen peroxide.<ref>Template:Cite journal</ref><ref>XP-Chloro Degradation Malachite green Template:US patent</ref> Reduction of methyl violet occurs in microorganisms but can be attained chemically using sodium dithionite.

Biodegradation

Biodegradation has been well investigated because of its relevance to sewage plants with specialized microorganisms. Two microorganisms that have been studied in depth are the white rot fungus and the bacterium Nocardia corallina.<ref>Template:Cite journal </ref><ref>Template:Cite journal</ref>

Photodegradation

Light alone does not rapidly degrade methyl violet,<ref>Template:Cite journal</ref> but the process is accelerated upon the addition of large band-gap semiconductors, titanium dioxide or zinc oxide.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

Other methods

Many other methods have been developed to treat the contamination of dyes in a solution, including electrochemical degradation,<ref>Template:Cite journal</ref> ion exchange,<ref>Template:Cite journal</ref> laser degradation, and absorption onto various solids such as activated charcoal.

See also

• Fuchsine
• Methylene blue
• Methyl blue
• Egyptian Blue
• Han Purple
• Fluorescein