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Petroleum Analysis
As with all properties of petroleum, a collection of standard test methods is instrumental in the
evaluation and assessment of the thermal properties. These standards allow petroleum refineries
and other geological and chemical processing plants to appropriately examine and process petroleum in a safe and efficient manner.
10.4.1 volAtIlIty
The volatility of a liquid or liquefied gas may be defined as its tendency to vaporize; that is, to change
from the liquid to the vapor or gaseous state. Because one of the three essentials for combustion in
a flame is that the fuel be in the gaseous state, volatility is a primary characteristic of liquid fuels.
The vaporizing tendencies of petroleum and petroleum products are the basis for the general
characterization of liquid petroleum fuels, such as liquefied petroleum gas, natural gasoline, motor
and aviation gasoline, naphtha, kerosene, gas oil, diesel fuel, and fuel oil (ASTM D2715). A test
(ASTM D6) also exists for determining the loss of material when crude oil and asphaltic compounds are heated. Another test (ASTM D20) is a method for the distillation of road tars that might
also be applied to estimating the volatility of high molecular weight residues.
For some purposes it is necessary to have information on the initial stage of vaporization. To supply this need, flash and fire, vapor pressure, and evaporation methods are available. The data from
the early stages of the several distillation methods are also useful. For other uses it is important to
know the tendency of a product to partially vaporize or to completely vaporize, and in some cases to
know if small quantities of high-boiling components are present. For such purposes, chief reliance
is placed on the distillation methods.
The flash point of petroleum or a petroleum product is the temperature to which the product
must be heated under specified conditions to give sufficient vapor to form a mixture with air
that can be ignited momentarily by a specified flame (ASTM D56, D92, and D93). The fire point
is the temperature to which the product must be heated under the prescribed conditions of the
method to burn continuously when the mixture of vapor and air is ignited by a specified flame
(ASTM D92).
From the viewpoint of safety, information about the flash point is of most significance at or
slightly above the maximum temperatures (30°C–60°C, 86°F–140°F) that may be encountered in
storage, transportation, and use of liquid petroleum products, in either closed or open containers. In
this temperature range the relative fire and explosion hazard can be estimated from the flash point.
For products with flash point below 40°C (104°F) special precautions are necessary for safe handling. Flash points above 60°C (140°F) gradually lose their safety significance until they become
indirect measures of some other quality.
The flash point of a petroleum product is also used to detect contamination. A substantially lower
flash point than expected for a product is a reliable indicator that a product has become contaminated with a more volatile product, such as gasoline. The flash point is also an aid in establishing
the identity of a particular petroleum product.
A further aspect of volatility that receives considerable attention is the vapor pressure of petroleum and its constituent fractions. The vapor pressure is the force exerted on the walls of a closed
container by the vaporized portion of a liquid. Conversely, it is the force that must be exerted on
the liquid to prevent it from vaporizing further (ASTM D323). The vapor pressure increases with
temperature for any given gasoline, liquefied petroleum gas, or other product. The temperature at
which the vapor pressure of a liquid, either a pure compound of a mixture of many compounds,
equals 1 atm (14.7 psi, absolute) is designated as the boiling point of the liquid.
In each homologous series of hydrocarbons, the boiling points increase with molecular weight and
structure also has a marked influence since it is a general rule that branched paraffin isomers have
lower boiling points than the corresponding n-alkane. In any given series, steric effects notwithstanding, there is an increase in boiling point with an increase in carbon number of the alkyl side chain.
This particularly applies to alkyl aromatic compounds where alkyl-substituted aromatic compounds
Petroleum Analysis
As with all properties of petroleum, a collection of standard test methods is instrumental in the
evaluation and assessment of the thermal properties. These standards allow petroleum refineries
and other geological and chemical processing plants to appropriately examine and process petroleum in a safe and efficient manner.
10.4.1 volAtIlIty
The volatility of a liquid or liquefied gas may be defined as its tendency to vaporize; that is, to change
from the liquid to the vapor or gaseous state. Because one of the three essentials for combustion in
a flame is that the fuel be in the gaseous state, volatility is a primary characteristic of liquid fuels.
The vaporizing tendencies of petroleum and petroleum products are the basis for the general
characterization of liquid petroleum fuels, such as liquefied petroleum gas, natural gasoline, motor
and aviation gasoline, naphtha, kerosene, gas oil, diesel fuel, and fuel oil (ASTM D2715). A test
(ASTM D6) also exists for determining the loss of material when crude oil and asphaltic compounds are heated. Another test (ASTM D20) is a method for the distillation of road tars that might
also be applied to estimating the volatility of high molecular weight residues.
For some purposes it is necessary to have information on the initial stage of vaporization. To supply this need, flash and fire, vapor pressure, and evaporation methods are available. The data from
the early stages of the several distillation methods are also useful. For other uses it is important to
know the tendency of a product to partially vaporize or to completely vaporize, and in some cases to
know if small quantities of high-boiling components are present. For such purposes, chief reliance
is placed on the distillation methods.
The flash point of petroleum or a petroleum product is the temperature to which the product
must be heated under specified conditions to give sufficient vapor to form a mixture with air
that can be ignited momentarily by a specified flame (ASTM D56, D92, and D93). The fire point
is the temperature to which the product must be heated under the prescribed conditions of the
method to burn continuously when the mixture of vapor and air is ignited by a specified flame
(ASTM D92).
From the viewpoint of safety, information about the flash point is of most significance at or
slightly above the maximum temperatures (30°C–60°C, 86°F–140°F) that may be encountered in
storage, transportation, and use of liquid petroleum products, in either closed or open containers. In
this temperature range the relative fire and explosion hazard can be estimated from the flash point.
For products with flash point below 40°C (104°F) special precautions are necessary for safe handling. Flash points above 60°C (140°F) gradually lose their safety significance until they become
indirect measures of some other quality.
The flash point of a petroleum product is also used to detect contamination. A substantially lower
flash point than expected for a product is a reliable indicator that a product has become contaminated with a more volatile product, such as gasoline. The flash point is also an aid in establishing
the identity of a particular petroleum product.
A further aspect of volatility that receives considerable attention is the vapor pressure of petroleum and its constituent fractions. The vapor pressure is the force exerted on the walls of a closed
container by the vaporized portion of a liquid. Conversely, it is the force that must be exerted on
the liquid to prevent it from vaporizing further (ASTM D323). The vapor pressure increases with
temperature for any given gasoline, liquefied petroleum gas, or other product. The temperature at
which the vapor pressure of a liquid, either a pure compound of a mixture of many compounds,
equals 1 atm (14.7 psi, absolute) is designated as the boiling point of the liquid.
In each homologous series of hydrocarbons, the boiling points increase with molecular weight and
structure also has a marked influence since it is a general rule that branched paraffin isomers have
lower boiling points than the corresponding n-alkane. In any given series, steric effects notwithstanding, there is an increase in boiling point with an increase in carbon number of the alkyl side chain.
This particularly applies to alkyl aromatic compounds where alkyl-substituted aromatic compounds