The water-soluble reaction product of a fatty acid ester and an alkali (usually sodium hydroxide),with glycerol as a byproduct. A soap is actually a specific type of salt, the hydrogen of the fatty acid being replaced by a metal, which in common soaps is usually sodium. Soap lowers the surface tension of water and permits emulsification of fat bearing soil particles. A typical commercial cleaning soap is made by reacting sodium hydroxide with a fatty acid. The lower the hydrogen content of the acid,the thinner is the soap. The byproduct of the reaction is glycerol. Many different carboxyl-containing substances are used, including rosin, tall oil, and vegetable and animal oils and fats (stearic, palmitic,and oleic acids).Olive oil is used for Castile soap and transparent soaps are made from decolorized fats. The specific gravity of soaps is slightly more than 1.0 and the inclusion of air gives a floating product. Water solutions of sodium soaps in bar,chip,or powder form are universally used as mild emulsifying detergents for washing textiles, skin, paint,etc.Medically,soap is used as an antidote for poisoning by ingestion of mineral acids or heavy metals.Liquid green soap is made with potassium hydroxide and a vegetable oil.
Heavy-metal soaps, loosely called metallic soaps, are those formed by metals heavier than sodium(aluminum, calcium,cobalt,lead,and zinc). These soaps are not water-soluble and specific types are used in lubricating greases, gel thickeners,and in paints as dryers and flatting agents. Napalm is an aluminum soap.
According to an ancient Roman legend, soap got its name from Mount
Sapo, where animals were sacrificed. Rain washed a mixture of melted
animal fat or tallow and wood ashes down into the clay soil along the Tiber River. It was found that this clay mixture cleaned the washed
clothes with much less effort.
The term soap is a class name for the sodium and potassium salts of
fatty acids. These fatty acids were found in animal fats and in plant oils
such as coconut oil, palm oil, olive oil, castor oil, or cottonseed oil.
Soaps are manufactured from a renewable source. The triglycerides (or
triesters of fatty acids) are the raw material for the production of soap.
The triglycerides occur widely in plants and animals.
Tallow and coconut oil are the principal fatty materials in soap making
in the United States. The palm oils, palm kernel oil, and their derivatives
are used in soap manufacture in many other parts of the world.
Greases, obtained from hogs and smaller domestic animals, are the
second most important source of glycerides of fatty acids. Coconut oil has
long been important in soap making. The soap from coconut oil is firm
and lathers well. It contains a large amount of the desired glycerides of
lauric and myristic acids [1-6].
The soap maker represents one of the larger consumers of chemicals,
especially caustic soda, salt, soda ash, caustic potash, sodium silicate,
sodium bicarbonate, and trisodium phosphate. Builders are inorganic
chemicals added to soap. In particular, tetrasodium pyrophosphate and
sodium tripolyphosphate were usually effective soap builders [1-6].
(1) The water-soluble reaction product of
a fatty acid ester and an alkali (usually sodium
hydroxide), with glycerol as by-product. For the
reaction, see saponification. A soap is actually a spe-
cific type of salt, the hydrogen of the fatty acid being
re
One of a number of sodium or potassium
compounds of fatty acids that are
commonly used to improve the cleansing
properties of water. Soap was the earliest
known DETERGENT. It is made by first reacting
vegetable oils and animal fats with a
strong solution of sodium or potassium hydroxide
to produce organic acids, such as
octadecanoic acid. The soap is then precipitated
out as the salt, e.g. sodium octadecanoate,
by adding excess sodium chloride.
In water, soap molecules break up to produce
ions, which are responsible for the
cleansing properties.
