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What
does the word wax bring to one’s mind? Bees or
maybe candles. Wax is a name applied originally to
naturally occurring esters of fatty acids and
certain alcohols. (Esters are fragment compounds
formed when there is a reaction between an acid and
an alcohol, with water being eliminated. Unlike
salts, esters are covalent compounds.) Now, however,
the name applies to both natural and manufactured
products resembling these esters. Waxes are composed
variously of esters, fatty acids, free alcohols, and
solid hydrocarbons.
Fatty
acids are organic compounds consisting of a
hydrocarbon chain, up to 24 carbon atoms long, with
a carboxyl group (-COOH) at one end. Saturated fatty
acids include palmitic and stearic acids, while
unsaturated fatty acids include oleic,
linoleic and linolenic acids. |
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Types of waxes
All waxes have a dull shine and a somewhat soapy or greasy texture.
They soften gradually on heating before ultimately forming a liquid.
Wax is a fatty substance of animal, vegetable, or mineral origin.
Lanolin (or wool grease) and ambergris (a wax produced in the
intestines of sperm whales and used in making cosmetics, perfumes,
ointments and polishes) are typical examples of animal waxes.
Bees
wax is yet another example of animal wax. Tallow, a form of suet
(hard fat) obtained from cattle and sheep and used to make candles
and soap is one more example of animal wax.
Plant
waxes occur on the exposed surfaces of many plants, protecting the
plant against excessive loss or gain of water. Mineral waxes are
obtained from petroleum. They vary in hardness. From the soft
petroleum jelly used in ointments to the hard paraffin wax used in
making candles and waxed paper for drink cartons, there is a vast
difference in the hardness of mineral waxes. In fact, most
commercial waxes come from petroleum. Waxes are used in the
manufacture of numerous items, including candles, polishes, waxed
paper, rust preventives, electrical insulators, paper coatings,
printing inks, and containers for food.
Vegetable
waxes usually occur as a waterproof coating on plants that grow in
hot, arid regions. These include carnauba wax obtained from the leaves of the carnauba
palm and candelilla wax. Both these waxes are used in hard polishes
such as car polish. From lac or shellac, a resinous substance
obtained from secretions of scale insects is obtained the sealing
wax. |
