Upload
leonling
View
9.545
Download
4
Embed Size (px)
Citation preview
Chemical is very important to human beings’ life
Almost everything that we use, we eat, we drink everyday
are related closely to chemistry
For examples:-The soap we use to bath
-The detergent we use to clean
the dirt
-The food additives to make
food tasted better
-The medicines tocure disease
Who discovers the soap? And when its history
started?
Since water is essential for life, the earliest people lived near water and knew something about its cleansing
properties - at least that it rinsed mud off their hands.
A soap-like material found in clay cylinders during the excavation of ancient Babylon is evidence that
soapmaking was known as early as 2800 B.C.
At about the same time, Moses gave the Israelites detailed laws governing personal cleanliness. He also related cleanliness to
health and religious purification.
The early Greeks bathed for aesthetic reasons and apparently did not use soap. Instead, they cleaned their bodies with blocks of clay, sand, pumice and ashes, then anointed themselves with oil, and scraped off the oil and dirt with a metal instrument. Clothes were washed without soap in streams.
Soap making was an established craft in Europe by the seventh
century. Vegetable and animal oils were used with ashes of plants,
along with fragrance.
Commercial soapmaking in the American colonies began
in 1608 AD
Large-scale commercial soapmaking occurred in 1791 when a French
chemist, Nicholas Leblanc, patented a process for making soda ash, or sodium carbonate. Soda ash is the
alkali obtained from ashes that combines with fat to form soap.
20 years later, Michel Eugene Chevreul, another French
chemist, discovered that the chemical nature and
relationship of fats, glycerine and fatty acids.
Also important to the advancement of soap technology was the mid-1800s
invention by the Belgian chemist, Ernest Solvay, of the ammonia process, which also used common table salt, or sodium
chloride, to make soda ash. Solvay's process further reduced the cost of
obtaining this alkali, and increased both the quality and quantity of the soda ash
available for manufacturing soap.
What forms SOAP?• sodium (Na) @ potassium (K) salts of
long- chain fatty acid
Fats/Oil
•the ionic head group is water-
soluble, the nonpolar tail insoluble
The structure of soap
Tail TailHead
hydrophobic hydrophilic
The structure of soap
The structure of soap
Tail
How SOAP & water can clean so much than water ?
Cleansing Action
•Hidrophilic part (head) attracted to water
Water molecules
Cleansing ActionDirt
(grease)
Hidrophobic part (tail)
likes to dissolved in
grease
Cleansing Action
•The droplets do not coagulate because of repulsion between negative charges on surface
•Scrubbing clothes helps to break the grease into small droplets
Cleansing Action•The droplets suspended in water & form emulsion
•Rinsing process could wash away these droplets & leaves surface clean
Cleansing Action
Cleansing Action
Detergent
•Soaps are made up of natural resources
•But detergents are made up of synthetic resources such as petroleum fractions
Structure of Detergent
Tail Head
Cleansing Action
•Cleansing action of detergent is just the same with soaps
Soap Detergent
Advantage• Biodegradable•Do not cause any pollution
• effective in both of soft & hard water•do not form scum in hard water (Mg2+ ,Ca 2+)•Do not form precipitate in acidic water
Disadvantage• form scum in hard water, cleansing action not effective•Form precipitate in acidic water
• Non-biodegradable• harm aquatic lives