Editing Bitumen (section)

=== Normal composition ===
The components of bitumen include four main classes of compounds:
* Naphthene aromatics ([[naphthalene]]), consisting of partially hydrogenated polycyclic aromatic compounds
* Polar aromatics, consisting of high [[molecular weight]] [[phenols]] and [[carboxylic acid]]s produced by [[partial oxidation]] of the material
* [[Saturated hydrocarbons]]; the percentage of saturated compounds in asphalt correlates with its softening point
* Asphaltenes, consisting of high molecular weight phenols and [[heterocyclic compound]]s

Bitumen typically contains, elementally 80% by weight of carbon; 10% hydrogen; up to 6% sulfur; and molecularly, between 5 and 25% by weight of asphaltenes dispersed in 90% to 65% maltenes.<ref>{{cite magazine | date=22 November 1999 |volume=77|issue=47 |page=81 | title=Asphalt |magazine=Chemical & Engineering News | author=Michael Freemantle | url=https://pubsapp.acs.org/cen/whatstuff/stuff/7747scit6.html}}</ref> Most natural bitumens also contain [[organosulfur compound]]s, [[nickel]] and [[vanadium]] are found at <10 parts per million, as is typical of some petroleum.<ref name=UllmannAsph/> The substance is soluble in [[carbon disulfide]]. It is commonly modelled as a [[colloid]], with [[asphaltene]]s as the dispersed phase and [[maltenes]] as the continuous phase.<ref>{{cite book|author=Muhammad Abdul Quddus|year=1992|title=Thesis submitted to Department of Applied Chemistry; University of Karachi|chapter=Catalytic Oxidation of Asphalt|publisher=Higher Education Commission Pakistan: Pakistan Research Repository|location=Pakistan|page=6, in ch. 2 pdf|chapter-url=http://eprints.hec.gov.pk/1171/1/891.html.htm|archive-url=https://web.archive.org/web/20110205060447/http://eprints.hec.gov.pk/1171/1/891.html.htm|archive-date=5 February 2011}}</ref> "It is almost impossible to separate and identify all the different molecules of bitumen, because the number of molecules with different chemical structure is extremely large".<ref>Muhammad Abdul Quddus (1992), p. 99, in ch. 5 pdf</ref>

Asphalt may be confused with [[coal tar]], which is a visually similar black, thermoplastic material produced by the [[destructive distillation]] of [[coal]]. During the early and mid-20th century, when [[town gas]] was produced, coal tar was a readily available byproduct and extensively used as the binder for road aggregates. The addition of coal tar to [[macadam]] roads led to the word "[[Tarmacadam|tarmac]]", which is now used in common parlance to refer to road-making materials. However, since the 1970s, when natural gas succeeded town gas, bitumen has completely overtaken the use of coal tar in these applications. Other examples of this confusion include [[La Brea Tar Pits]] and the Canadian [[tar sands]], both of which actually contain natural bitumen rather than tar. "Pitch" is another term sometimes informally used at times to refer to asphalt, as in [[Pitch Lake]].