You will hear a lecture about the early history of personal cleanliness and soap.
First, you have some time to look at questions 31 to 40.
Now listen carefully and answer questions 31 to 40.
Today, products for bathing, washing clothes, cleaning dishes and maintaining the home are ordinary parts of daily life.
Yet the wide range we rely on is largely a modern development, dating mainly from the 20th century.
The story of cleanliness begins much earlier.
Prehistoric communities generally settled near water because it was essential for survival, and they soon recognized one simple cleansing effect.
Water could rinse mud from their hands.
Evidence from ancient Babylon shows that people understood a form of soapmaking by about 2800 BC.
Archaeologists found clay cylinders whose inscriptions describe boiling fats together with ashes.
Although this resembles a soap recipe, the cylinders do not explain what the substance was used for.
The ancient Greeks bathed mainly for appearance and apparently did not wash with soap.
They rubbed their bodies with sand, pumice or ash, applied oil and then removed the mixture of oil and dirt with a metal scraper called a stridgil.
Their clothes were washed in streams without soap.
In ancient Germany and Gaul, people also made a soap-like mixture from melted animal fat and ash.
Instead of using it chiefly for washing, however, they used it to colour their hair red.
A Roman legend links the name soap with Mount Sappo.
Animal sacrifices supposedly left fat on the ground there, and rain carried this fat and wood ash into clay beside the river Tiber.
Women discovered that the resulting mixture made washing clothes much easier.
As Roman society developed, public bathing expanded too.
Around 312 BC, aqueducts began supplying water to the famous Roman baths.
Bathing became highly popular, and by the second century AD, the physician Galen was recommending soap for both cleaning and medical purposes.
After Rome fell in 467 AD, bathing declined across much of Europe.
Poor personal hygiene and unsanitary living conditions contributed to repeated outbreaks of disease during the Middle Ages, most famously the Black Death in the 14th century.
Even so, soap-making became a recognised European craft.
Guilds protected their methods, and makers combined plant or animal oils with ash.
Perfume also began to be added, and specialised soaps gradually appeared for shaving, washing hair, bathing and laundering.
A crucial advance towards mass production came in 1791.
The French chemist Nicolas LeBlanc patented an economical process for converting salt into soda ash, the alkali that reacts with fat, to produce soap.
His method supplied large quantities of reliable, inexpensive soda ash.
About 20 years later, another French chemist, Michel Eugène Chevreau, explained the chemical relationships among fats, glycerine and fatty acids.
His research established the scientific basis of fat and soap chemistry, turning soap-making from a craft into a science.
Further 19th century improvements made production cheaper and easier.
Soap had long been treated as a luxury, and was heavily taxed in several countries.
When this tax disappeared in the 19th century, ordinary people could afford soap more readily, and standards of cleanliness rose.
Its wider use then encouraged the development of gentler bathing soaps and products suitable for the washing machines available by the start of the 20th century.
That is the end of part four.
You now have one minute to check your answers to part four.
