METHOD OF OBTAINING FIXED OILS, PROPERTIES, CONSTITUENST

METHOD OF OBTAINING FIXED OILS: -
Most of the fixed oils and fats are obtained by expression from plant or animal tissue. The material is first ground and then subjected to hydraulic pressure and to heat when necessary. first expression is called “virgin”.
Some oils are extracted by the use of volatile solvent. Animal fats and oil are obtained by the process known as ‘rendering’ which consults of heating the tissues until fat melts and separates mechanically.

PROPERTIES: -1. They are greasy to touch and leave spot on filter paper.
2. They are all lighter than water and insoluble there in, but soluble in ether, chloroform and other water immiscible solvents.
3. When purified, they are nearly colourless and of a bland odour, and taste with very little distinctiveness.
4. When heated strongly they undergo decomposition with the production of acrid, inflammable vapours, and when ignited they burn with sooty flame. Acridity is due to the formation of Acrolein (propenal).
5. They have propensity to undergo hydrolysis to yield glycerol and fatty acids.

CONSTITUENTS:
These glycerides, 1) Olein 2) Palmitin 3) Stearin, are common to many fixed oils.
Olein, is glyceryl trioleate [C3H5 (C18H33O2) 3] liquid at ordinary temp.
Palmetin’ is Glyceryltripalmtate [C3H5(C16H31O2)3] solid at ordinary temperature (m.p.60).
Stearin’ is glyceryltristearate [C3H5 (C18H35O2) 3], solid (m.p. 71).