M

Methylene blue

IUPAC: [7-(dimethylamino)phenothiazin-3-ylidene]-dimethylazanium chloride

C16H18ClN3S Indicators CAS 61-73-4
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Quick Reference
Formula / NotationC16H18ClN3S
CAS Number61-73-4
Molecular Weight319.9
Melting Point100 to 110 °C (with decomposition)
SolubilityIn water, 43,600 mg/L at 25 °C.
AppearanceDark green crystals or powder with a bronze-like luster; Solutions in water or alcohol are deep blue; [ChemIDplus]
Also Known As[7-(dimethylamino)phenothiazin-3-ylidene]-dimethylazanium chloride; 61-73-4; Basic blue 9; Methylthioninium chloride; Solvent blue 8; Swiss Blue; Methylene Blue anhydrous; Chromosmon; C.I. Basic Blue 9; Methylene Blue N
CategoryIndicators

What is Methylene blue?

Methylene blue is an organic chloride salt having 3,7-bis(dimethylamino)phenothiazin-5-ium as the counterion. A commonly used dye that also exhibits antioxidant, antimalarial, antidepressant and cardioprotective properties. It has a role as an antioxidant, an antimicrobial agent, a physical tracer, an antidepressant, an EC 3.1.1.8 (cholinesterase) inhibitor, an antimalarial, an EC 1.4.3.4 (monoamine oxidase) inhibitor, an acid-base indicator, a fluorochrome, a neuroprotective agent, a histological dye, a cardioprotective agent and an EC 4.6.1.2 (guanylate cyclase) inhibitor. It contains a 3,7-bis(dimethylamino)phenothiazin-5-ium.

Formula & Notation

C16H18ClN3S

IUPAC Name: [7-(dimethylamino)phenothiazin-3-ylidene]-dimethylazanium chloride

Other Names / Synonyms: [7-(dimethylamino)phenothiazin-3-ylidene]-dimethylazanium chloride; 61-73-4; Basic blue 9; Methylthioninium chloride; Solvent blue 8; Swiss Blue; Methylene Blue anhydrous; Chromosmon; C.I. Basic Blue 9; Methylene Blue N

Properties & Characteristics

Appearance: Dark green crystals or powder with a bronze-like luster; Solutions in water or alcohol are deep blue; [ChemIDplus]. Molecular formula: C16H18ClN3S. Molecular weight: 319.9 g/mol. Melting point: 100 to 110 °C (with decomposition). Solubility: In water, 43,600 mg/L at 25 °C.. Vapor pressure: 0.00000013 [mmHg].

Physical Data

PropertyValue
Melting Point100 to 110 °C (with decomposition)
Molecular Weight319.9
SolubilityIn water, 43,600 mg/L at 25 °C.
AppearanceDark green crystals or powder with a bronze-like luster; Solutions in water or alcohol are deep blue; [ChemIDplus]

Uses & Applications

Used as a pH indicator in acid-base titrations, analytical chemistry, and chemical education demonstrations.

Safety Information

May be irritant or toxic in concentrated form. Handle with care. Consult SDS before use.

Always consult the SDS/MSDS before handling any chemical. This information is for educational purposes only.

Key Facts

Term Methylene blue
Formula C16H18ClN3S
CAS Number 61-73-4
Molecular Weight 319.9
Category Indicators
Synonyms [7-(dimethylamino)phenothiazin-3-ylidene]-dimethylazanium chloride; 61-73-4; Basic blue 9; Methylthioninium chloride; Solvent blue 8; Swiss Blue; Methylene Blue anhydrous; Chromosmon; C.I. Basic Blue 9; Methylene Blue N

Frequently Asked Questions

Methylene blue is an organic chloride salt having 3,7-bis(dimethylamino)phenothiazin-5-ium as the counterion. A commonly used dye that also exhibits antioxidant, antimalarial, antidepressant and cardioprotective properties. It has a role as an antioxidant, an antimicrobial agent, a physical tracer, an antidepressant, an EC 3.1.1.8 (cholinesterase) inhibitor, an antimalarial, an EC 1.4.3.4 (monoamine oxidase) inhibitor, an acid-base indicator, a fluorochrome, a neuroprotective agent, a histological dye, a cardioprotective agent and an EC 4.6.1.2 (guanylate cyclase) inhibitor. It contains a 3,7-bis(dimethylamino)phenothiazin-5-ium.

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Editorial standards: Chemical data is sourced from peer-reviewed literature, CAS Registry, NIST WebBook, and PubChem. Safety information reflects guidance from OSHA, ECHA, and IAEA. For educational purposes only — always consult official SDS documentation and qualified professionals before handling chemicals.