Neutral Red

CAS Number: 553-24-2
Molecular Weight: 288.78
PubChem Substance ID: 24897804
EC Number: 209-035-8

General description

Neutral red (C.I. 50040) is a protonated diaminophenazine dye. It is aminodimethylaminomethylphenazinehydrochloride, C15H17N4Cl.


Neutral red has multiple staining applications that include its use as a nuclear stain, counterstain in the Gram procedure, either alone, or as a component of the Twort stain (a fast green-neutral red mixture). Neutral red staining is also a viability assessment method used for the detection of viable yeast cells in dandruff samples and of mussel larvae. Neutral red is also recommended for use in viability assessment as it is selectively absorbed by lysosomes and other acidic organelles in cells. It is also used for supravital staining of living blood cells.
Useful as an indicator for preparing neutral red paper, and as a biological stain.

Biochem/physiol Actions

Neutral red is a widely used cationic fluorochrome that is known to accumulate in the Golgi complex and nuclei after first staining lysosomes.



Form powder
Quality Level 200
composition Dye content, ≥90%
technique(s) titration: suitable
pH 6.8-8.0, red to yellow
mp 290 °C (dec.) (lit.)
solubility water: 10 mg/mL, dark red
application(s) diagnostic assay manufacturing
storage temp.


SMILES string Cl.CN(C)c1ccc2nc3cc(C)c(N)cc3nc2c1