Bitumen
From Free net encyclopedia
Image:Bitumen.jpg Bitumen is a category of organic liquids that are highly viscous, black, sticky and wholly soluble in carbon disulfide. Asphalt and tar are the most common forms of bitumen.
In British English, 'bitumen' is often used interchangeably with both 'asphalt' and 'tar'. In American English, 'bitumen' is most commonly used in engineering jargon to explicitly include both asphalt- and tar-based materials. In Australian English, 'bitumen' is used as the generic term for road surfaces.
Bitumen in the form of asphalt is obtained by fractional distillation of crude oil. Bitumen being the heaviest and being the fraction with the highest boiling point, it appears as the bottommost fraction.
Bitumen in the form of tar is obtained by the destructive distillation of organic matter, usually bituminous coal.
Bitumen is primarily used for paving roads. It is also the prime feed stock for petroleum production from tar sands currently under development in Alberta, Canada.
In the past, bitumen was used to waterproof boats, and even as a coating for buildings; it is possible, for example, that the city of Carthage was easily burnt down due to extensive use of bitumen in construction.
Vessels for the heating of bitumen or bituminous compounds are usually excluded by public liability insurance policies.
Most geologists believe that naturally occurring deposits of bitumen are formed from the remains of ancient, microscopic algae and other once-living things. These organisms died and their remains were deposited in the mud on the bottom of the ocean or lake where they lived. Under the heat and pressure of burial deep in the earth, the remains were transformed into materials such as bitumen, kerogen, or petroleum.
A minority of geologists, proponents of the theory of abiogenic petroleum origin, believe that bitumen and other hydrocarbons heavier than methane originally derive from deep inside the mantle of the earth rather than biological detritus.
See also
de:Bitumen fr:Bitume nl:Bitumen pl:Bitumy pt:Betume ru:Битум vi:Bitum zh:瀝青