A residue from heat treatment and distillation of petroleum fractions. It is solid
at room temperature, consists of a complex mixture of numerous predominantly aromatic
and alkyl-substituted aromatic hydrocarbons
, and exhibits a broad softening range instead of a defined melting
The hydrogen aromaticity
(ratio of aromatic to total hydrogen atoms) varies between 0.3 and 0.6. The aliphatic
hydrogen atoms are typically present in alkyl groups
substituted on aromatic rings or as naphthenic hydrogen.
PAC, 1995, 67, 473
(Recommended terminology for the description of carbon as a solid (IUPAC Recommendations
on page 499
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook