Methyl blue, also known as Cotton blue, Helvetia blue, Acid blue 93, or C.I. 42780, is a chemical compound

Chemical compound

A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...

 with the molecular formula C₃₇H₂₇N₃Na₂O₉S₃. It is used as a stain

Staining (biology)

Staining is an auxiliary technique used in microscopy to enhance contrast in the microscopic image. Stains and dyes are frequently used in biology and medicine to highlight structures in biological tissues for viewing, often with the aid of different microscopes...

 in histology

Histology

Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...

. Methyl blue stains collagen

Collagen

Collagen is a group of naturally occurring proteins found in animals, especially in the flesh and connective tissues of mammals. It is the main component of connective tissue, and is the most abundant protein in mammals, making up about 25% to 35% of the whole-body protein content...

 blue in tissue

Biological tissue

Tissue is a cellular organizational level intermediate between cells and a complete organism. A tissue is an ensemble of cells, not necessarily identical, but from the same origin, that together carry out a specific function. These are called tissues because of their identical functioning...

 sections. It is soluble in water and slightly soluble in ethanol

Ethanol

Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...

. It can be used in the Mallory's connective tissue

Connective tissue

"Connective tissue" is a fibrous tissue. It is one of the four traditional classes of tissues . Connective Tissue is found throughout the body.In fact the whole framework of the skeleton and the different specialized connective tissues from the crown of the head to the toes determine the form of...

 stain and Gömöri trichrome stain

Gomori trichrome stain

Gömöri trichrome stain is a stain used on muscle tissue.It can be used to test for certain forms of mitochondrial myopathy.It is named for George Gömöri, who developed it in 1950.-External links:...

. It is used in differential staining

Differential staining

Differential Staining is a general term that can refer to a number of specific processes. Generally, it is used to describe staining processes which use more than one chemical stain...

. It can also be used to mediate electron transfer in microbial fuel cell

Microbial fuel cell

A microbial fuel cell or biological fuel cell is a bio-electrochemical system that drives a current by mimicking bacterial interactions found in nature....

s.

Methyl blue is also used to stain fungal cell walls.
Methyl blue is also available in mixture with water blue

Water blue

Water blue, also known as aniline blue, Acid blue 22, Soluble Blue 3M, Marine Blue V, or C.I. 42755, is a chemical compound used as a stain in histology. Water blue stains collagen blue in tissue sections...

, under name Aniline Blue WS

Aniline Blue WS

Aniline Blue WS, also called aniline blue, China blue, or Soluble blue, is a mixture of methyl blue and water blue. It may also be either one of them....

, Aniline blue, China blue, or Soluble blue.

Methyl blue should not be confused with methyl violet

Methyl violet

Methyl violet is a family of organic compounds that are mainly used as dyes. Depending on the amount 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...

 or methylene blue

Methylene blue

Methylene blue is a heterocyclic aromatic chemical compound with the molecular formula C16H18N3SCl. It has many uses in a range of different fields, such as biology and chemistry. At room temperature it appears as a solid, odorless, dark green powder, that yields a blue solution when dissolved in...

, two other stains.

Methyl blue is also used to treat thallium

Thallium

Thallium is a chemical element with the symbol Tl and atomic number 81. This soft gray poor metal resembles tin but discolors when exposed to air. The two chemists William Crookes and Claude-Auguste Lamy discovered thallium independently in 1861 by the newly developed method of flame spectroscopy...

 poisoning. It binds to the thallium.

See also

• Potassium ferrocyanide
  Potassium ferrocyanide
  Potassium ferrocyanide is the inorganic compound with formula K4[Fe6]•3H2O. It is the potassium salt of the coordination complex [Fe6]4-. This salt forms lemon-yellow monoclinic crystals.-Synthesis:...
  
  
• Potassium ferricyanide
  Potassium ferricyanide
  Potassium ferricyanide is the chemical compound with the formula K3[Fe6]. This bright red salt contains the octahedrally coordinated [Fe6]3− ion. It is soluble in water and its solution shows some green-yellow fluorescence.-Preparation:...
  
  
• Methylene blue
  Methylene blue
  Methylene blue is a heterocyclic aromatic chemical compound with the molecular formula C16H18N3SCl. It has many uses in a range of different fields, such as biology and chemistry. At room temperature it appears as a solid, odorless, dark green powder, that yields a blue solution when dissolved in...
  
  
• Egyptian Blue
  Egyptian Blue
  Egyptian blue is chemically known as calcium copper silicate . It is a pigment used by Egyptians for thousands of years. It is considered to be the first synthetic pigment. The pigment was known to the Romans by the name caeruleum...
  
  
• Han Purple
  Han Purple
  Han purple and Han blue are synthetic barium copper silicate pigments that were developed in China at least 2,000 years ago....
  
  
• Gentian violet
• Fluorescein
  Fluorescein
  Fluorescein is a synthetic organic compound available as a dark orange/red powder soluble in water and alcohol. It is widely used as a fluorescent tracer for many applications....