Advantages of syntbetic detergents over soaps
1. Synthetic detergents can be used even in case of hard water whereas soaps fail to do so.
2. Synthetic detergents can be used in the acidic medium while soaps cannot because of their hydrolysis to free acids.
3. Synthetic detergents are more soluble in water and hence, form better lather than soaps.
4. Synthetic detergents have a stronger cleansing action than soaps.
Chemistry in Colouring Matter
The natural or synthetic colouring matter which are used in solution to stain materials especially fabrics are called dyes.
All colouring substances are not dyes, e. g., azobenzene, a coloured substance does „ not act as dye. A dye have following characteristics:
1. It must have a suitable colour. 2. It can be fixed on the fabric either directly or with the help of mordant.
3. It must be resistant to the action of water, acid and alkalies. The groups, responsible for colour, are called chromophore, e. g.,
Classification of Dyes on the Basis of Constitution
( i) Nitro or nitroso dye Chromophore NO2 or NO group, Auxochrome =-OH group, e. g., picric acid, martius yellow, Gambine, naphthol yellow-S.
( ii) Azo dye, e. g., bismark brown, methyl orange, methyl red, congo red, etc.( iii) Anthraquinone dye e. g., alizarin
( iv) Indigo is the oldest known dye. Other examples are tyrian purple, indigosol.