Basic dyes are the class of dyes, that are most commonly synthetic. Their primary nature is to act as bases, and are actually aniline dyes. Initially their color base prevents them from being water soluble. They can be made so with the base being converted into a salt. At the chemical level, basic dyes are typically cationic or positively charged. Basic dyes display cationic functional groups like -NR3+ or =NR2+. Since basic dye is a stain that is cationic or positively charged and it is the reason that it reacts well with material that is anionic or negatively charged.

Basic dyes consists of amino groups, or alkylamino groups, as their auxochromes. Synthetic dye that was discovered by Perkin incidentally was a basic dye. Some prominent examples of basic dyes are the following, methylene blue, crystal violet, basic fuchsin safranin, etc. An example of a basic dye that has amino groups as their auxochrome is pararosanilin or basic red 9 (according to the strict colour index system of classification) example of alkylamino groups is methylene blue or basic blue 9. Basic Blue 9 is a very popular dye that has vast use. The following table gives a few vital information regarding the dye basic blue 9.

A basic chemical structure of Basic Blue 9

• High Tinctorial strength
• Moderate substantivity
• Relatively economical
• Wide shade range
• Includes some of the most brilliant synthetic dyes
• Shows good brightness

• Poor shade stability
• High acid content
• Coloured backwaters
• Very poor lightfastness
• Preferential dyeing

Basic dyes have an extensive use for dyeing of cut flowers, dried flowers, dyeing of jute, coir etc. But perhaps now theoptimum use lies in the dyeing of acrylic fibre. For dyeing this range, a new range of 'modified' basic dyes were developed. It became perfectly suitable for dyeing of this material. If the reason behind the success of Basic dyes is analysed, it would be seen that the positively charged cations of the Basic dyes gets attracted towards the negatively charged anions in the acrylic fibre. Acylic polymers have anionic groups attached to it. They are most commonly the sulphonate group, -SO₃-, followed closed by the carboxylate group, -CO₂-. This reaction of the cation and anion results in salt linkages. Basic dye do not show absolutely any migration in acrylic fibers under normal dyeing conditions. Other popular applications include dyeing leather. They are preferred in leather dyeing as they can get combined easily with vegetable-tanned leather thus doing away with mordant. Basic dyes also find its use in colouration of papers.