If you search for information about fractional distillation of petroleum, many sources place petrol above naphtha, while others do the reverse. Is there not a strict definition of what these compounds are?

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    $\begingroup$ Petrol and naphtha are not pure compounds and represent variable mixtures of compounds with similar properties. So there isn't really a strict definition of either. $\endgroup$
    – matt_black
    Commented Apr 2 at 20:55

1 Answer 1


As matt_black commented, “petrol” (gasoline) and naphtha are not pure compounds and represent variable mixtures of compounds with similar properties.” Thus, there isn't really a strict definition of either of them, and some sources further categorized both of them just as naphtha based on the distillation processes. For example, see below two depictions of fractional distillation processes:

fractional distillation processes

Abdullah Ashraf of Qatar University has published a content of his BS thesis through ResearchGate, which is worth mentioning here. The main concern of this paper is the distillation process of crude oil. Here, he has reported the ideas of different processes of distillations and their steps (see the image in right hand side above), which could be trustworthy since it is from the country of major crude petroleum producer. Briefly, in the paper, it explains naphtha as mix of 5 to 9 carbon atom alkanes $(\ce{C5-C9})$ collected at boiling range of $\pu{60-100 ^\circ C}$ while gasoline as mix of of alkanes and cycloalkanes containing 5 to 12 carbon atoms $(\ce{C5-C12})$ collected at boiling range of $\pu{40-205 ^\circ C}$. According to aforementioned paper, state of matter of naphtha has given to be gas and that of gasoline is mentioned as liquid. Further, naphtha is an intermediate that will be further processed to make gasoline.

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    $\begingroup$ Note that there is big confusion in terminology when different languages or regions are considered, as the same or similar terms may mean different things, or different terms for the same thing. E.g., in Czech, what is marked as naphtha on the picture, is called "petroleter"(more volatile) or surový(raw) benzín(gasoline) (less volatile). We use the term nafta for diesel oil. Other languages or regions have their own traps. It is easy to get diesel oil in NW Africa if you call for gasoline(whatever term ). One needs to use the term spirit there. $\endgroup$
    – Poutnik
    Commented Apr 3 at 5:12

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