difference between acidic and basic stains
Stains are classified based on the pH of their chromophore (color bearing ion) into acidic, basic and neutral. Acidic dyes have anionic chromophore eg., sodium+ eosinate-. Basic dyes have cationic chromophore eg., methylene blue+ chloride-. Acidic dyes combine more strongly with cytoplasmic components of bacteria, especially the nucleus that is basic in nature.