Page 115 - Medicinal Plants_PharmD general

Tests for fixed oils:
1. 1% Solution of osmic acid: the oil globules are coloured black.
2. Diluted tincture of alkanna: the oil globules are coloured red after

30 min.
3. Sudan III: the oil globules are coloured red.
4. A cold mixture of equal parts of a saturated solution of potash and

strong solution of ammonia slowly saponifies fixed oils and fats. After
some hours characteristic soap crystals may be observed (C.F volatile
oil).
Fats and oils may become rancid on keeping due to:
1- Oxidation by air oxygen.
2- Bacterial putrefaction.

Waxes:

Waxes are esters of fatty acids with high molecular weight monohydric
alcohols e.g. beeswax.

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