Synthetic Dyes and Their Applications (Part-2)

The presence of more water solublising group is characteristics of anionic mono azo dyes. Sulphonic groups are used almost exclusively for this purpose because these are readily accessible and are strong electrolytes and therefore almost completely dissociated in all acidity ranges occurring in the aqueous solution. These dyes are widely used for paper and leather, and their metal salts are used as pigments. The term "Acid Dyes" denotes a large group of anionic dyes with a relative low molecular weight that carry 1 to 3 sulphonic acid groups. They are mainly mono azo compounds but also includes bisazo, triphenyl methine, 4-oxoquinazoline derivatives and other name "Acid Dyes" is derived from the dyeing process, they are applied to wool [1-4], silk [5,6] and nylon. A solvent dye is a dye which is soluble in an organic solvent and is commonly introduced in the form of a solution in an organic solvent. Solvent dyes [1-2] are used to impart colour to organic solvents, hydrocarbon fuels, waxes, lubricants, plastics, and other hydrocarbon based non-polar materials. Their molecules are typically non-polar or little polar and they do not undergo ionization in solvent.