Acid dyes are water-soluble dyes and generally applied to wool with the addition of acid or acid salts.Rung acid dyes can also be applied on polyamide, silk, leather and to some extent on paper also. Rung acid dyes consist of dyes belonging to azo, 1:1 metal complex, 1:2 metal complex and 1:2 metal complex dyes with solubilising groups. They can be applied by different dyeing methods depending on the class they belong. Rung acid dyes demonstrate generally good fastness properties.