Page 115 - Medicinal Plants_General

CH2OCOR 1 CH2OH R1COONa
CHOH + R2COONa
CHOCOR + 3 NaOH CH2OH R3COONa
2 glycerol
soap
CH2OCOR3

Fixed oil

According to the ability of the oil to absorb oxygen and to form
hard film on exposure to air i.e. according to the amounts and degree of
unsaturation of the fatty acids present, they are calssified into:
1. Drying oil which contains high percentage of unsaturated fatty acids
and forming hard films e.g. linseed oil.
2. Semi-drying forming a pasty film.
3. Non- drying e.g. olive oil.

Methods of preparation:

 Both fixed oils and fats are obtained by expression extraction of
the plant or animal tissue. In this process the material is subjected to
hydraulic pressure and heat is used if necessary.

 The oils obtained in the first expression extraction (cold pressed) have
a high commercial value such as olive oil where the first expression is
known by virgin olive oil, but for subsequent expressions is necessary
to subject them to a process of purification.

 The fixed oils are frequently treated for its clarification and finally
are filtered.

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