Chemistry In Action Test - 2

Basic dyes contain NH₂ or -NR₂ groups as colour bearing group or colour enhancing groups they are generally used for Wool, cotton, leather, paper, polyester, nylon etc. e.g. aniline yellow, crysodine G, butter yellow, malachite green etc.

Direct dyes stick to the fibre through hydrogen bonding. They belong to the class of azo dyes. They are used to dye the fabric directly by placing it in not aqueous solution of dye e.g. martius yellow, Congored etc.

Vat dyes are insoluble compounds which up on reduction give soluble (lencoform) product. The product may be either coloured or colourless and have affinity for specific fabrics e.g. Indigo.

Disperse dye are usually applied in the form of dispersion of finely divided dye in a soap solution in the presence of Phenol, Cresol, Benzoic acid etc. They are mainly used to dye decron, nylon, synthetic fibre. Example Celliton (blue).

Malachite green prepared by the condensation of Benzaldehyde and dimethyl aniline.

Fluorescin is obtained by the reaction of Phthalic anhydride and resorcinol.

Trans form of Indigo is more stable.

Indigo is dark blue solid insoluble in water.

Methyl orange is yellow in alkaline medium and red in acedic medium.