Standard Test Method for
Calculation of Carbon Distribution and Structural Group
Analysis of Petroleum Oils by the n-d-M Method1
This standard is issued under the fixed designation D 3238; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1.1 This test method covers the calculation of the carbon
distribution and ring content (Note 1) of olefin-free petroleum
oils from measurements of refractive index, density and
molecular weight (n-d-M).2 This test method should not be
applied to oils whose compositions are outside the following
1.1.1 In terms of carbon distribution— up to 75 % carbon
atoms in ring structure; percentage in aromatic rings not larger
than 1.5 times the percentage in naphthenic rings.
1.1.2 In terms of ring content—up to four rings per molecule with not more than half of them aromatic. A correction
must be applied for oils containing significant quantities of
NOTE 1—The composition of complex petroleum fractions is often
expressed in terms of the proportions of aromatic rings (RA), naphthene
rings (RN) and paraffin chains (CP) that would comprise a hypothetical
mean molecule. Alternatively, the composition may be expressed in terms
of a carbon distribution, that is, the percentage of the total number of
carbon atoms that are present in aromatic ring structures (% C A),
naphthene ring structures (% CN), and paraffin chains (% Cp).
1.2 The values stated in SI units are to be regarded as the
standard. The values in parentheses are for information only.
1.3 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
Click below to download Astm D 3238 – 95 (Reapproved 2000)e1 pdf free
Click here to download Astm D 3237 – 02 Pdf Free Download