Characteristics and Properties of Crude Oil and Its Products


API API gravity defined in Equation 2.2 a,b...i Correlation constants in various equations

BIvh Blending index for viscosity of liquid hydrocarbons (see Equation 2.64), dimensionless

CH Carbon-to-hydrogen weight ratio

Dab Binary (mutual) diffusion coefficient (diffusivity) of component A in B. cm2/s

DA.,„iX Effective diffusion coefficient (diffusivity) of component Aina mixture, cm2/s

dr Liquid density at temperature T and 1 atm, g/cm3

d20 Liquid density at 20°C and 1 atm, g/cm3

f, Fugacity of component i in a mixture defined by Equation 2.85, bar

fiL Fugacity of pure liquid i at T and P, bar

GOR Gas-to-oil ratio (scf/bbl)

/ Refractive index parameter defined in Equation 2.11

Kw Watson (UOP) К factor defined by Equation 2.8 kj Henry’s law constant defined by Equation 2.84, bar

к gas,water Henry’s law constant of a gas in water (Equation 2.85), bar

M Molecular weight, g/mol [kg/kmol]

n Sodium D line refractive index of liquid at 20°C and 1 atm, dimension

less, defined in Equation 2.10

Nc Carbon number (number of carbon atoms in a hydrocarbon molecule)

Pc Critical pressure, bar

p»'i> Vapor (saturation) pressure, bar

P, Reduced pressure (= P/Pc), dimensionless

Prv“i’ Reduced vapor pressure at a given temperature (= P'aP/Pc), dimensionless R Universal gas constant, 8.314 J/mol-K

R; Refractivity intercept in Equation 2.9

SG Specific gravity of liquid substance at 15.5°C (60°F) defined by Equation 2.1, dimensionless

SGg Specific gravity of gas substance at 15.5°C (60°F) defined by Equation 2.3, dimensionless Th Boiling point, К

Tc Critical temperature, К

T, Flash point, К

Тм Melting (freezing point) point, К

V Molar volume, cmVgmol

Vc Critical volume (molar), cm-Vmol (or critical specific volume, cmVg)

xlvj Weight fraction of component i in a mixture (usually used for liquids),


Xp, xN, xA Fractions (i.e., mole) of paraffins, naphthenes, and aromatics in a petroleum fraction, dimensionless

y, Mole fraction of i in a mixture (usually used for gases), dimensionless

Z Compressibility factor (= PV/RT), dimensionless

Zt. Critical compressibility factor (Z=PlVJRTL), dimensionless


p Absolute (dynamic) viscosity, cp [mPa-s]; also used for dipole moment

v Kinematic viscosity defined by Equation 2.7, cSt [mm2/s]

v39(ioo) Kinematic viscosity of a liquid at 39°C (100°F), cSt (10-2 cm2/s)

  • 6, Solubility parameter for i, (J/cm3)l/2 or (cal/cm3)1'2
  • 0 A property of hydrocarbon such as: M, Tc, Pc, Vc, I, d, Th, ...

p Density at a given temperature and pressure, g/cm3

о Surface tension, dyn/cm [= mN/m]

crH Surface tension of a hydrocarbon at a given temperature, dyn/cm

owo Interfacial tension of oil and water at a given temperature, dyn/cm

со Acentric factor defined by Equation 2.5, dimensionless

% Viscosity parameter defined by Equation 2.72, (cp)-1

Y, Activity coefficient of component i in liquid solution, dimensionless


A Aromatic

N Naphthenic

P Paraffinic

T Value of a property at temperature T

r Reduced property, dimensionless

A reference state for T and P oo Value of a property at M -» oo

  • 20 Value of a property at 20°C
  • 39(100) Value of kinematic viscosity at 39°C (100°F) 99(210) Value of kinematic viscosity at 99°C (210°F)


API-TDB American Petroleum Institute - Technical Data Book EOS Equation of state

IUPAC International Union of Pure and Applied Chemistry

GOR Gas-to-oil ratio

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