ASTM D2502-92(2002)

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An American National Standard
Designation: D 2502 – 92 (Reapproved 2002)
Standard Test Method for
Estimation of Molecular Weight (Relative Molecular Mass) of
Petroleum Oils From Viscosity Measurements
This standard is issued under the fixed designation D 2502; 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. Scope viscosity is established by reference to a tabulation of H
function versus 100°F viscosity. The H value and the 210°F
1.1 This test method covers the estimation of the mean
viscosity are then used to estimate the molecular weight from
molecular weight (relative molecular mass) of petroleum oils
a correlation chart.
from kinematic viscosity measurements at 100 and 210°F
(37.78 and 98.89°C). It is applicable to samples with molecu-
4. Significance and Use
lar weights in the range from 250 to 700 and is intended for use
4.1 This test method provides a means of calculating the
with average petroleum fractions. It should not be applied
mean molecular weight (relative molecular mass) of petroleum
indiscriminately to oils that represent extremes of composition
oils from another physical measurement.
or possess an exceptionally narrow molecular weight (relative
4.2 Molecular weight (relative molecular mass) is a funda-
molecular mass) range.
mental physical constant that can be used in conjunction with
1.2 Values stated in inch-pound units are to be regarded as
other physical properties to characterize hydrocarbon mixtures.
the standard. The values given in parentheses are provided for
information purposes only.
5. Procedure
1.3 This standard does not purport to address all of the
5.1 Determine the kinematic viscosity of the oil at 100 and
safety concerns, if any, associated with its use. It is the
210°F (37.78 and 98.89°C) as described in Test Method D 445.
responsibility of the user of this standard to establish appro-
5.2 Look in Table 1 for 100°F (37.78°C) viscosity and read
priate safety and health practices and determine the applica-
the value of H that corresponds to the measured viscosity.
bility of regulatory limitations prior to use.
Linear interpolation between adjacent columns may be re-
quired.
2. Referenced Documents
5.3 Read the viscosity - molecular weight chart for H and
2.1 ASTM Standards:
210°F (98.89°C) viscosity. A simplified version of this chart is
D 445 Test Method for Kinematic Viscosity of Transparent
shown in Fig. 1 for illustration purposes only (Note 1).
and Opaque Liquids (the Calculation of Dynamic Viscos-
3 Interpolate where necessary between adjacent lines of 210°F
ity)
viscosity. After locating the point corresponding to the value of
2.2 ASTM Adjuncts:
H (ordinate) and the 210°F viscosity (superimposed lines), read
Molecular Weight of Petroleum Oils from Viscosity Mea-
4 the molecular weight along the abscissa.
surements (D 2502)
Example:
3. Summary of Test Method Measured viscosity, cSt:
100°F (37.78°C) = 179
3.1 The kinematic viscosity of the oil is determined at 100
210°F (98.89°C) = 9.72
and 210°F (37.78 and 98.89°C). A function “ H” of the 100°F
Look in Table 1 for 179 and read the corresponding value H
= 461.
This test method is under the jurisdiction of ASTM Committee D02 on
Using H = 461 and 210°F viscosity = 9.72 in conjunction
Petroleum Products and Lubricants and is the direct responsibility of Subcommittee
with chart gives molecular weight (relative molecular
D02.04 on Hydrocarbon Analysis.
mass) = 360 (see Fig. 1).
Current edition approved Aug. 15, 1992. Published October 1992. Originally
published as D 2502 – 66 T. Last previous edition D2502 – 82.
NOTE 1—A 22 by 28-in. (559 by 711-mm) chart available as an adjunct
Hirschler, A. E., Journal of the Institute of Petroleum, JIPEA, Vol 32, 1946, p.
to this test method was used in cooperative testing of the method. If other
133.
charts are used, the precision statements given in the Precision Section
Annual Book of ASTM Standards, Vol 05.01.
Available from ASTM Headquarters. Order ADJD2502 will not apply.
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D 2502 – 92 (2002)
6. Precision and Bias
6.1 The precision of this test method as obtained by statis-
tical examination of interlaboratory test results is as follows:
6.1.1 Repeatability—The difference between successive test
results obtained by the same operator with the same apparatus
under constant operating conditions on identical test material,
would in the long run, in the normal and correct operation of
the test method, exceed the value 3 g/mol only in one case in
twenty.
6.1.2 Reproducibility—The difference between two single
and independent results, obtained by different operators, work-
ing in different laboratories on identical test material, would in
the long run, in the normal and correct opera
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