Acid dyes based on a salt of a sulfuric, carboxylic or the phenolic organic acid. The salts are often sodium or ammonium salts. Basic dyes are cationic (+ve charged) and so will react with the material that is (-ve) negatively charged. Basic dyes are usually applied to Acrylic fibers.

Is the dye basic acid?

Acid dyes are anionic, soluble in water and are essentially applied from acidic bath. These dyes possess acidic groups, such as SO3H and COOH and are applied on wool, silk and nylon when ionic bond is established between protonated –NH2 group of fibre and acid group of dye.

Are negative dyes acidic or basic?

Basic dyes, which carry a positive charge, are more commonly used for staining than are negatively charged acidic dyes. Because opposite charges attract, basic dyes stain the many negatively charged components of cells, including nucleic acid and many proteins, whereas acidic dyes are repelled.