The composition of raw wool will vary greatly because of the many complicated factors. The important constituent is known as keratin. It
differs from others on account of its high sulfur content. The compositions of
raw wool are shown.
Chemical compositions in wool fibre
Composition Percentage (%)
- Keratin 45-75
- Grease 5-15
- Moisture 10-12
- Suint 2-12
- Sand and dirt 4-30
- Vegetable matter 0-5
Grease
It is an impurity in raw wool, insoluble in water but can
be partially emulsified by it. It is soluble in organic solvents. Wool grease
is an ester of high molecular weight fatty acids and a monohydric alcohol i.e.
cholesterol (C27 H45OH) or is cholesterol. This is not fat but wax. Wool wax
has the power of absorbing large quantities of water.
Suint
This is soluble in water and can be isolated from the raw
wool by aqueous extraction. It consists of potassium salts of fatty acids and
organic amino acids and is a complex mixture.
Sand and dirt
The fibre in its natural state contains a considerable
amount of dirt. This is held by adhesive action of the grease and falls away
when the latter is removed during scouring. Wool keratin is composed of fine
elements, carbon, hydrogen, nitrogen, oxygen, and sulfur.
The compositions are :
- Carbon 50-53%
- hydrogen 6-7%
- Nitrogen 16-18%
- Oxygen 21-25%
- Sulfur 7-5.0%
The element of the composition of keratin is nearly the same for a different type of wool but the sulfur content varied within great limits. Most
of the stability and instability of wool depend upon functional nitrogen and
sulfur group
