Editing Diesel fuel (section)

== Chemical analysis ==

=== Chemical composition ===
[[File:Dieselrainbow.jpg|thumb|right|Diesel [[immiscible|does not mix]] with water. This picture also showcases the phenomenon of [[Thin-film interference]].]]
In the United States, petroleum-derived diesel is composed of about 75% [[saturated hydrocarbon]]s (primarily [[Alkane|paraffins]] including [[Isoparaffin#Linear alkanes|''n'']], [[Isoalkane#Isomerism|''iso'']], and [[Cycloalkane|cycloparaffins]]), and 25% [[aromatic hydrocarbon]]s (including [[naphthalene]]s and [[alkylbenzenes]]).<ref>Agency for Toxic Substances and Disease Registry (ATSDR). 1995. ''[http://www.atsdr.cdc.gov/toxprofiles/tp75-c3.pdf Toxicological profile for fuel oils]''. Atlanta, GA: [[United States Department of Health and Human Services|U.S. Department of Health and Human Services]], Public Health Service</ref> The average chemical formula for common diesel fuel is C<sub>12</sub>H<sub>23</sub>, ranging approximately from C<sub>10</sub>H<sub>20</sub> to C<sub>15</sub>H<sub>28</sub>.<ref>{{cite book|last=Date|first=Anil W.|date=7 March 2011|title=Analytic Combustion: With Thermodynamics, Chemical Kinetics and Mass Transfer (Google eBook)|url=https://books.google.com/books?id=uPZXiVTCEcIC&q=chemical+composition+of+diesel+fuel+c12h23,+c10h20,+c15h28|publisher=Cambridge University Press|page=189|isbn=978-1-107-00286-9|access-date=9 October 2014}}</ref>

=== Chemical properties ===
{{further|Diesel exhaust|Gel point (petroleum)}}
Most diesel fuels freeze at common winter temperatures, while the temperatures greatly vary.<ref name="nrel" /> Petrodiesel typically freezes around temperatures of {{convert|-8.1|°C|°F|abbr=on}}, whereas biodiesel freezes between temperatures of {{convert|2|to|15|C|F}}.<ref name="nrel">{{cite report|author=National Renewable Energy Laboratory staff|date=January 2009|title=Biodiesel Handling and Use Guide|url=http://www.biodiesel.org/docs/using-hotline/nrel-handling-and-use.pdf?sfvrsn=4|publisher=National Renewable Energy Laboratory|edition=Fourth|page=10|docket=NREL/TP-540-43672|access-date=18 July 2014|archive-url=https://web.archive.org/web/20160306103447/http://biodiesel.org/docs/using-hotline/nrel-handling-and-use.pdf?sfvrsn=4|archive-date=6 March 2016|url-status=dead}}</ref> The viscosity of diesel noticeably increases as the temperature decreases, changing it into a gel at temperatures of {{convert|-19|to|-15|°C|°F|abbr=on}}, that cannot flow in fuel systems. Conventional diesel fuels vaporise at temperatures between 149&nbsp;°C and 371&nbsp;°C.<ref name="ufa1">{{cite web|url=https://www.staroilco.net/diesel-fuel-technical-review-from-chevron/|title=Diesel Fuel Technical Review|author=<!--Staff writer(s); no by-line.-->|year=2007|website=www.staroilco.net|publisher=Chevron}}</ref>

Conventional diesel [[flash point]]s vary between 52 and 96&nbsp;°C, which makes it safer than petrol and unsuitable for spark-ignition engines.<ref name=gasfp>{{cite web |url= http://www.engineeringtoolbox.com/flash-point-fuels-d_937.html|title= Flash Point — Fuels|access-date=January 4, 2014}}</ref> Unlike petrol, the flash point of a diesel fuel has no relation to its performance in an engine nor to its auto ignition qualities.<ref name="ufa1" />