TRANQUILIZERS : These are chemical compounds used to relieve from pain. Commonly known as psychotherapeutic drugs these generally includes the derivatives of barbituric acid. for eg. veronal, amytal, nembutal, luminal, seconal etc.

DYES: These are coloured chemical substances capable of imparting coloursto the textiles, foodstuffs, leather, paper, cosmetics etc.

On the basis of their applications, they are classified into:

 

ACID DYES: They are applied in presence of acidic solutions. They are usually applied to wool, silk, nylon etc. They do not have affinity with cotton. ex. are orange-I, orange-II, methyl red, methyl orange etc.

BASIC DYES: These dyes contain -NH2 or -NR2 groups as colour bearing groups. They are generally used for leather, wool, cotton, paper, polyester, nylon etc.. ex. are aniline yellow, butter yellow etc.

DISPERSE DYES: They are generally 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 dacron, nylon. ex. are celliton fast pink B and celliton fast blue B etc.

 

VAT DYES: These dyes are insoluble compounds, which on reduction gives soluble leuco form product. The reduced product is generally colourless and has affinity for specific fabrics. For ex. indigo dye.

 

MORDANT DYES: A mordant is any substance which can be fixed to the fibre and which can be dyed later on. Mostly hydroxides or basic salts of chromium, aluminium and iron are used as mordants. A mordant dye imparts different colours in presence of different mordants.

 

                           On the basis of structure, dyes are classified into:nitro dyes( e.g. martius yellow), azo dyes( eg. orange-I), pthalein dyes(eg. phenolphthalein), triphenymethane dye(eg. malachite green), indigoid dye( eg. indigo) and anthraquinone dye(eg.alizarin).