Preparation, Chemical Constituents and Uses of Silk
Silk are the fibres obtained from the cocoons of Bombyx mori (Mulberry silkworm) and other species of Bombyx and also from Antheraea species of the family Bombycidae.
Fine quality of silk is manufactured in Japan, Italy, China and France. A large quantity of silk is also produced in India.
Preparation of silk:
The larvae of the silk worm produces fibroin fibres from the glands in their stomach. These fibres get united due to a gum like secretion called sericin and forms a cocoon. These cocoons are not allowed to grow into insects, they are heated to 60-80 degrees by exposing them to steam. These exposed cocoons are put in hot water to dissolve the sericin and for the separation of fibres. Silk threads are very fine, solid, smooth and are yellow in colour. They are insoluble in water and alcohol. Silk is soluble in cuoxam solution, sulphuric acid and concentrated hydrochloric acid.
Chemical constituents of Silk:
Silk contains a protein known as fibroin. This on hydrolysis yields amino acids alanine and glycine.
Uses of Silk:
Silk is used to prepare special types of sutures, sieves and ligatures.
Preparation, Chemical Constituents, Chemical Test and Uses of Wool
Wool or wool fibres are obtained from the fleece of sheep Ovis aries, of the family Bovidae. Large quantities of wool is manufactured in Russia, Australia, USA, Argentina and in India.
Preparation of Wool:
The hairs, which form the fleece of the sheep are removed at shearing time. They are then processed to remove wool fat and dirt. The cleaned and defatted wool is bleached, washed again and dried. Wool hairs are elastic, smooth, lustrous, curly, hygroscopic and slippery to touch. These hairs have a tendency to cling together. It is insoluble in sulphuric acid, concentrated hydrochloric acid and cuoxam solution.
Chemical constituents of Wool:
It contains a sulphur containing protein, keratin which is rich in sulphur containing aminoacid cysteine.
Chemical test for Wool:
When lead acetate is added to a solution of wool in caustic soda, a black precipitate is obtained due to high sulphur content.
Uses of Wool:
Wool is used as a filtering and straining medium. It is also used for manufacturing of dressings like domette and crepe bandages and flannel.