Neutral red

• 3- amino-7- dimethylamino -2- methylphenazin · hydrochloride
• N8, N8 ,3 -trimethyl- 2,8- phenazindiaminmonohydrochlorid
• Toluylenrot
• C. I. 50040

Dark green to black powder

Fixed

Moderately in water (50 g · l-1 at 25 ° C ) and alcohol

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Neutral red is a red phenazine dye.

It dyes cotton violet red tannin-treated (non -fading ). The dye is (color change from red to yellow at pH 6.8 to 8.0 ) and as a redox indicator for biological studies such as the determination of cell viability by neutral red as an indicator test, since it is not toxic.

Neutral red is from pH 13 to 7.5 prior uncharged and is yellow in color. Uncharged neutral is membrane permeable. From pH 7.4 and acid dye is protonated and takes red color ( pKa 5.89). As the cation, neutral membranes is no longer able to penetrate. It therefore accumulates in acidic compartments of cells to (so-called ion trapping or ion trap ).