Methylene blue

Athanor · official

C₁₆H₁₈ClN₃S · 319.9 g/mol

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

Also called methylthioninium chloride, basic blue 9, Swiss blue, ProvayBlue

Reagents Rings

Open in Athanor

Drawn from its SMILES with RDKit

DangerHarmful if swallowed · Causes serious eye damage · Harmful to aquatic life with long lasting effects

Names and identifiers

IUPAC name: [7-(dimethylamino)phenothiazin-3-ylidene]-dimethylazanium chloride
Synonyms: methylthioninium chloride, basic blue 9, Swiss blue
+ 39 more
ProvayBlue, Basic blue 9, Methylthioninium chloride, Solvent blue 8, Swiss Blue, C.I. Basic Blue 9, Chromosmon, Methylene Blue anhydrous, Methylene Blue N, Methylene Blue BB, Urolene blue, Methylenium ceruleum, Methylene Blue chloride, Bleu de methylene, Methylene Blue A, Methylene Blue B, Methylene Blue D, Methylene Blue G, External Blue 1, Tetramethylene Blue, Calcozine Blue ZF, Methylene Blue BD, Methylene Blue BP, Methylene Blue BX, Methylene Blue BZ, Methylene Blue FZ, Methylene Blue GZ, Methylene Blue NZ, Methylene Blue SG, Methylene Blue SP, Methylene Blue ZF, Methylene Blue ZX, Methylthionine chloride, Methylenblau, Methylene Blue 2B, Methylene Blue BBA, Methylene Blue BPC, Methylene Blue HGG, Methylene Blue IAD
Molecular formula: C₁₆H₁₈ClN₃S
Empirical formula: C₁₆H₁₈ClN₃S
Molecular weight: 319.9 g/mol
Exact mass: 319.09100
CAS number: 61-73-4
PubChem CID: 6099
Canonical SMILES: CN(C)C1=CC2=C(C=C1)N=C3C=CC(=[N+](C)C)C=C3S2.[Cl-]
Isomeric SMILES: CN(C)C1=CC2=C(C=C1)N=C3C=CC(=[N+](C)C)C=C3S2.[Cl-]
InChI: InChI=1S/C16H18N3S.ClH/c1-18(2)11-5-7-13-15(9-11)20-16-10-12(19(3)4)6-8-14(16)17-13;/h5-10H,1-4H3;1H/q+1;/p-1
InChIKey: CXKWCBBOMKCUKX-UHFFFAOYSA-M
Molfile

Names, InChI and the identifiers from PubChem, retrieved 2026-10-14.

Physical properties

TemperaturePressureDensity

Appearance: Solutions have a deep blue color (methylene blue zinc-free dye)[1]
Odor: Slight odor[1]
Melting point: 100-110 °C (decomposes)[1]
Solubility in water: In water, 43,600 mg/L at 25 °C.[1]
2 values
From Hazardous Substances Data Bank (HSDB), the most authoritative source here.
Value As written Source
–shown In water, 43,600 mg/L at 25 °C. [1] Hazardous Substances Data Bank (HSDB)cites Baughman GL et al; Dye Solubilities. In: Advances in Color Chemistry. Freeman M, Peters MT, eds., Elsevier (1993)
– Soluble in glacial acetic acid and glycerol; insoluble in xylene and oleic acid, in ethanol 2%, and in acetone 0.5%. [1] Hazardous Substances Data Bank (HSDB)cites Kirk-Othmer Encyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984., p. V3: 379 (1978)

Value	As written	Source
–shown	In water, 43,600 mg/L at 25 °C.	[1] Hazardous Substances Data Bank (HSDB)cites Baughman GL et al; Dye Solubilities. In: Advances in Color Chemistry. Freeman M, Peters MT, eds., Elsevier (1993)
–	Soluble in glacial acetic acid and glycerol; insoluble in xylene and oleic acid, in ethanol 2%, and in acetone 0.5%.	[1] Hazardous Substances Data Bank (HSDB)cites Kirk-Othmer Encyclopedia of Chemical Technology. 3rd ed., Volumes 1-26. New York, NY: John Wiley and Sons, 1978-1984., p. V3: 379 (1978)

Each value as its source reports it, with the source's number after it (listed under References). Where several sources report a property, the row shows the value most of them agree on, the rule the app uses; open the values to see every one.

Calculated

Heavy atoms: 21
Rings: 3
Aromatic rings: 1
Fraction sp³ carbons (Fsp3): 0.25
H-bond donors: 0
H-bond acceptors: 3 computed here · PubChem 4
Rotatable bonds: 1
TPSA (Å²): 19.1 computed here · PubChem 43.9
Formal charge: 0
Complexity: 483 PubChem
Stereocenters: None
Double-bond geometry: None specified
Point group: C1 of one 3D conformer with its hydrogens, by Athanor’s engine (as in the app)

Elemental analysis

C60.08%
H5.67%
Cl11.08%
N13.14%
S10.03%

Isotope pattern

Each peak is a nominal mass with its abundance-weighted exact mass, as a percentage of the tallest, from IUPAC natural isotope abundances.

Computed from the structure with RDKit 2026.09 when this page was built, beside PubChem's own computed values from its record; where the two differ, both are shown.

Predicted

log P: -0.5 Crippen (Wildman and Crippen 1999)
log S (water solubility): -1.94 ESOL (Delaney 2004), log mol/L
Synthetic accessibility: 2.89 SA score, 1 easy to 10 hard (Ertl and Schuffenhauer 2009)

Drug-likeness: Lipinski’s rule of five

Molecular weight ≤ 500: 319.86
log P ≤ 5 (Crippen): -0.5
H-bond donors ≤ 5: 0
H-bond acceptors ≤ 10: 3

Passes all four rules.

¹³C NMR shifts, predicted

Predictions, not measurements; each names its method. A measured log P, where a source reports one, is under Physical properties.

Safety

Danger

Most widely reported: 273 company reports to ECHA. Source [2].

Corrosive
Harmful or irritant

H302Harmful if swallowed (91.6% of reports)
H318Causes serious eye damage (25.6% of reports)
H412Harmful to aquatic life with long lasting effects (10.3% of reports)

Precautionary statements: P264, P264+P265, P270, P273, P280, P301+P317, P305+P354+P338, P317, P330, P501

View all classifications (3)

[2] European Chemicals Agency (ECHA)This chemical does not meet GHS hazard criteria for 8.1% (22 of 273) of reports.
[2] European Chemicals Agency (ECHA) · 273 reports · DangerH302, H318, H412
[2] European Chemicals Agency (ECHA) · 2 reports · DangerH302, H318

Storage

Keep container tightly closed in a dry and well-ventilated place. Storage class (TRGS 510): Non Combustible Liquids.[1]
Commercially available methylene blue 10-mg/mL solution for IV use should be stored at 20-25 °C, but may be exposed to temperatures ranging from 15-30 °C.[1]

Safety data sheets on the supplier’s page: TCI (Tokyo Chemical Industry), A2B Chem, LGC Standards.

Always read the supplier’s safety data sheet before working with it.

Spectra

Experimental spectra held by these sources; each link opens the source's own record.

Literature

Reading PubChem, OpenAlex and GSRS…

Bioactivity

Reading ChEMBL…

References

[1]Hazardous Substances Data Bank (HSDB) · Public domain (US NLM) · via PubChem · retrieved 2026-10-14
[2]European Chemicals Agency (ECHA) · ECHA legal notice: reuse with acknowledgement · via PubChem · retrieved 2026-10-14
[3]SpectraBase · Linked only · via PubChem · retrieved 2026-10-14
·Calculated values: computed by Athanor with RDKit 2026.09 from the structure.
·Literature on PubChem

Data last updated 2026-10-14.