Ufa State Academy for the Economy and Service. Translated from Khimiya i Tekhnologiya Topliv i
Masel, No.4, pp. 46 – 49, July – August, 2009.
0009-3092/09/4504–0288 © 2009 Springer Science+Business Media, Inc.
Chemistry and Technology of Fuels and Oils, Vol. 45, No. 4, 2009
METHODS OF ANALYSIS
DETERMINING THE MEAN MOLECULAR MASS FOR CRUDE OIL
AND OIL RESIDUES FROM COLOR CHARACTERISTICS
M. Yu. Dolomatov and G. U. Yarmukhametova
The mean molecular mass is a major characteristic of a crude oil or oil product. To determine the molecular
masses of light oil fractions (gasoline, diesel, light gasoils, and so on), Voinov’s is the most common method, in
which one calculates it from the boiling point of the fraction. However, Voinov’s method  is not applicable to oil
residues containing high-molecular tarry and asphaltene substances. Their mean molecular masses are determined
by cryoscopic methods or from spectroscopic data .
We have devised a method of determining the mean molecular masses for crude oils and oil residues from
the color characteristics (CC). The theoretical basis is provided by the correlations between the physicochemical
properties (PCP) in multicomponent hydrocarbon systems (color-property correlation) [3-5].
It has been established that there is a linear correlation between the PCP and the CC for solutions of
substances in optically transparent solvents in the form of the following relation for most multicomponent
where Z represents the physicochemical properties, including the mean molecular mass M for hydrocarbon systems;
are parameters having the dimensions of the corresponding property (these parameters in a given
colorimetric system are dependent on the solution concentration, the particular physicochemical property, the
type of radiation source, and the class of substance); H is one of the quantitative CC for solutions of these
substances as determined in various colorimetric systems, e.g., the color coordinate or coloration in the systems
XYZ and RGB for particular standard light sources.
One determines B
by least-squares fitting to a linear approximation for the data on crude oils and
oil products with known mean molecular masses and color characteristics.
The color of any object that is not self-luminous is determined  by the flux of reflected or transmitted
radiation from a definite light source as perceived by eye. It is dependent on the capacity of the object to absorb
or reflect radiation in the visible region (absorption spectrum or reflection spectrum), as well as on the spectrum
of the radiation source acting on the object, and on the capacity of a standard observer to perceive that radiation