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Crude glycerol is a product of a purity of less than 95 % (calculated on the weight of the dry product). It may be obtained either by cleavage of fats or oils or synthetically from propylene. It is of varying quality according to the method of production, e.g. :
(1) Obtained by hydrolysis with water, acids or alkalis, it is a sweetish liquid with a not unpleasant odour and ranges in colour from yellowish to brown. (2) Obtained from glycerol lyes, it is a pale yellow liquid with an astringent taste and a disagreeable odour. (3) Derived from the residues of soap-making, it is a blackish-yellow liquid with a sweetish flavour (sometimes tasting of garlic, if very impure) and a more or less disagreeable odour. (4) Obtained by catalytic and enzymatic hydrolysis, it is generally a liquid of disagreeable taste and odour, containing large quantities of organic substances and mineral matter.
Crude glycerol may also be obtained from inter-esterification of oils or fats with other alcohols.
The heading also includes glycerol waters, which are by-products of the production of fatty acids, and glycerol lyes, which are by-products of the production of soap. The heading excludes : (a) Glycerol of a purity of 95 % or more (calculated on the weight of the dry product) (heading 29.05). (b) Glycerol put up as a medicament or with added pharmaceutical substances (heading 30.03 or30.04). (c) Perfumed glycerol or glycerol with added cosmetics (Chapter 33).
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