Rhodamine dye family

Rhodamine B in water solution
by Aleksander Sobolewski

Description

Red to violet colored several synthetic red rhodamine dyes that are derived from xanthene, and therefore a specific subset of triarylmethane dyes. Rhodamine dyes are unique in that they fluoresce brightly and are used as tracers and indicators in several biotechnical applications, including medical imaging. They lack the lightfastness needed for fabric dyes and paint colors. Rhodamine dyes can be precipitated metallic compounds such as phosphotungstic or phosphomolybdic acid to make them more lightfast. Such compounds are called Rhodamine toners.

The most commonly used rhodamine dyes are:

Name	CI Number	Formula	Other names	Laked form	Comments
Rhodamine 6G	45160	C28H31N2O3Cl	Rhodamine 590		fluorescence microscopy and laser dyes, pH indicators; water tracer
			Basic Red 1
			Pigment Red 81	phosphotungstomolybdic acid salt	fluorescent pink brightness; primarily used in offset, water-based, solvent-based, and UV-curable inks; also used in plastics, coating and textile printing.; also called fast Pink Toner
			Pigment Red 169	copper ferrocyanide salt	bright bluish red with easy dispersion and good lightfastness; used in printing inks, industrial coating, various plastics and textile printing.
Rhodamine B	45170	C28H31CIN2O3	Rhodamine 610		fluorescence microscopy and laser dyes, pH indicators; water tracer
			Basic Violet 10
			D&C Red #19		formerly used in drugs and cosmetics but was removed from list in 1984 as a suspected carcinogen
			Solvent red 49		fluorescent red dye used in wood stains and coating, printing inks and leather finishes.
			Pigment Violet 1	phosphotungstomolybdic acid salt	bright reddish-violet with high color strength and good lightfastness; used in printing inks, textile printing, and, in some cases, plastics due to its high gloss and vivid shade
			Pigment Red 173	aluminum salt	brilliant pink to magenta used in inks, powder coatings, industrial paints, colored glass and plastic industries; Extensively used in cosmetic products; also called Rhodamine red and Cosmetic Rubine

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Resources and Citations

• Richard S. Lewis, Hawley's Condensed Chemical Dictionary, Van Nostrand Reinhold, New York, 10th ed., 1993
• Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
• The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998
• Wikipedia: Rhodamine Accessed Feb 2026