This dye has been widely used in many staining methods, but its commonest use is probably as a simple red nuclear counterstain. It is an indicator as well as a dye. It changes from red to yellow over the pH range 6.8 - 8.0. It has also been incorporated into bacteriological growth media.
The Merck Index gives the names nuclear fast red and kernechtrot as synonyms for neutral red. These two names are usually applied to another dye, CI 60760, which can be used as a red nuclear stain when mordanted with potassium alum. If a technique calls for nuclear fast red or kernechtrot, it is probably this latter dye to which it refers, not neutral red.
R. D. Lillie.
Conn's Biological Stains
Williams & Wilkins, Baltimore, MD., U.S.A.
Aldrich chemical catalogue, 1992
Aldrich Chemical Company, Milwaukee, WI, USA.
Edward Gurr, (1971)
Synthetic dyes in biology, medicine and chemistry
Academic Press, London, England.
Susan Budavari, Editor, (1996)
The Merck Index, Ed. 12
Merck & Co., Inc., Whitehouse Station, NJ, USA