LIPIDS OILS, FATS, AND WAXES; SOAP - Archaeological Chemistry - page 312

TABLE 77 Lipids: Oils, Fats, and Waxes

Lipids Examples Uses

Fats Butter Food

Tallow Making candles

Oils
Drying oils

Linseed oil Making paint

Nondrying oils Olive oil, soybean oil Food

Waxes Beeswax Making molds and candles

Lanolin Cosmetics

TEXTBOX 57
THE LIPIDS

The lipids are a large group of organic compounds including oils , fats , and
waxes . Akin to the carbohydrates, the molecules of the lipids are composed
of only three elements: carbon, hydrogen, and oxygen. They differ from
the carbohydrates, however, in their chemical properties and in that they
are insoluble in water and lubricious to the touch. If lipids are exposed to
the environment, particularly to oxygen in the air, for extended periods of
time, they are oxidized. Some oils (known as the drying oils ), for example,
solidify when oxidized. Most other oils, as well as the fats, do not solidify
when oxidized but become rancid , gradually developing an unpleasant
taste and exuding an objectionable stale odor (Gunstone 2004).

FIGURE 69 The triglycerides. “Triglycerides” is a generic name for the oils and
fats, which are also known as “lipids.” The molecules of all triglycerides consist
of three molecules of fatty acids bonded to one of glycerol (an alcohol also known
as “glycerine”). The molecules of the fatty acids are made up of long chains of
atoms of carbon linked to each other; the chain length generally varies from about
16 to 22 carbon atoms. All the chains of the triglycerides may be of the same
length (as illustrated), only two the same, or all of different lengths (see Table
78).