In chemistry, soap is a salt of a fatty acid. Soaps are mainly
used as surfactants for washing, bathing, and cleaning, but they
are also used in textile spinning and are important components
of lubricants. Soaps for cleansing are obtained by treating
vegetable or animal oils and fats with a strongly alkaline
solution. Fats and oils are composed of triglycerides; three
molecules of fatty acids are attached to a single molecule of
glycerol. The alkaline solution, which is often called lye
(although the term "lye soap" refers almost exclusively to soaps
made with sodium hydroxide), brings about a chemical reaction
known as saponification. In saponification, the fats are first
hydrolyzed into free fatty acids, which then combine with the
alkali to form crude soap. Glycerol (glycerine) is liberated and
is either left in or washed out and recovered as a useful
byproduct, depending on the process employed. Soaps are key
components of most lubricating greases, which are usually
emulsions of calcium soap or lithium so