Color Index Acid Red 29 is a chemical compound belonging to the class of azo dyes and the application group of acid dyes. It is the simplest chromotropic dye and was originally used to dye wool.
Synthesis Acid Red 29 is synthesized via the diazotization of aniline using sodium nitrite and hydrochloric acid, followed by the azo coupling of the resulting diazonium salt with chromotropic acid.
Use Acid Red 29 is used to dye wool a bluish-red hue. Treatment with chromium salts, such as potassium dichromate, produces a distinct color change from red to violet.
Acid Red 29 is used in histological staining—such as the Gömöri trichrome stain—in combination with aniline blue and hematoxylin.
Acid Red 29 is used in the complexometric titration of thorium.
History The production of this dye was patented by Hoechst in 1890.
As with other chromotropic acid-based dyes, the patent literature describes its primary application as wool printing.
References