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Rolling On and On
| Article
# : |
16497 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
5 / 1989 |
2,917 Words |
| Author
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George B. Kauffman
George B. Kauffman is professor of chemistry at California
State University, Fresno. A Guggenheim Fellow, he is a
contributing editor to four journals and the author of
fifteen
books and more than 950 articles on chemistry, the history of
science and technology, and chemical education. |
Crude rubber, sometimes called "gum-elastic," was known by the awkward name of caoutchouc until Joseph Priestley, the discoverer of oxygen, proposed the name rubber because the substance would erase pencil marks from paper. Although rubber possessed the valuable properties of elasticity, plasticity, strength, durability, non-conductivity of electricity, and resistance to water, products manufactured from it hardened in winter, softened and became sticky in summer, were attacked by solvents, and smelled bad.
In 1839 the American inventor Charles Goodyear, after more than five years of unceasing experiments, carelessly brought a piece of cloth coated with natural rubber mixed with lead monoxide or litharge and sulfur into contact with a hot stove. As a result of its chemical reaction with sulfur at elevated temperatures, the rubber "charred like leather." Goodyear called this process vulcanization after Vulcan, the Roman god of fire. This method not only removed the odor from the natural rubber, but also transformed it into a more useful form that did not harden in the cold or become soft and sticky in hot weather.
Natural Rubber
Pictures and carvings by the ancient Egyptians, Ethiopians, and other African and Asian peoples depicted games with bouncing rubber balls, and the Indians of the Amazon basin in tropical South America were familiar with the properties and uses of this peculiar natural substance long before Columbus' explorations brought knowledge of rubber to Europe.
The Indians made balls from the milky, white fluid called latex by smoking it on a wooden paddle to evaporate the water and cure the rubber. The first mention of practical uses for rubber was made in 1615 by a Spanish chronicler who reported that the natives brushed latex onto their cloaks to waterproof them and also made crude waterproof shoes and bottles by coating earthen molds and allowing them to dry.
In 1735 interest in rubber was revived when the French mathematical geographer Charles-Marie de La Condamine, who had headed an expedition to South America, sent back to France several rolls of crude rubber together with a description of products fabricated from it by the natives. The report also described caoutchouc as the condensed sap of the tree Hevea brasiliensis, whose first accurate botanical account was given in 1775.
Because the substance hardened so
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