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PHYSICAL PROPERTIES OF PETROLEUM




The colour of petroleum varies from light yellow to red, while some very dark grades are opaque. The higher the specific gravity, the darker the oil.

The nature and composition of crude oil usually determines its odour. Unsaturated hydrocarbons, sulphur and certain nitrogen compounds are responsible for disagreeable odours. Crude petroleum from the USSR, Rumania and California has an aromatic odour. Pennsylvania petroleum has an agreeable gasoline-like odour. Other oils vary in odour depending on the quantity of light hydrocarbons present in the oil, and of the impurities present. The petroleum from South Texas and Mexico has a strong disagreeable odour, due to hydrogen sulphide and other sulphur compounds. Petroleum is lighter than water. The specific gravity is influenced by physical factors and by the chemical composition of the crude oil. It varies from 0.7684 to 0.992.

The viscosity, or the measure of the resistance to flow, is an important factor with lubricating oils. Crude petroleums are quite different in viscosity. Some are very mobile, while others, like Mexican crude, are quite viscid. Heavy petroleum in general is composed to a large extent of these hydrocarbons. The viscosity increases with the density. The viscosities of oils of the same specific gravity, but from different sources, are not always the same. This is due to the difference in chemical composition.

ISOMERIZATION

When chemical substances have the same molecular formula and molecular weight but different properties, they are called isomers (of each other) and the reaction of transformation of one isomer into another is called isomerization. The reason for this phenomenon lies in the molecule.

There are, for example, two different compounds with the chemical formula C4H10:

 

CH3 – CH2 – CH2 – CH3 and CH3 – CH - CH3

|

CH3

n-butane iso-butane

 

These compounds have different properties.

Isomerism is prevalent among more complex compounds. Thus glucose is one of 16 isomeric sugars of the composition C6H12O6.

 

NATURAL GAS

Natural gas is an inflammable gas that occurs in the earths crust and is found with or near accumulations of crude oil. Being in gaseous form, it may occur alone in separate reservoirs.

Typical natural gas consists of hydrocarbons having a very low boiling point. Methane (СН4), the fundamental member of the methane series, with a boiling point of – 254o F, makes up approximately 85 per cent of the typical gas. Ethane (С2Н6), with a boiling point of – 128o F, is present in amounts up to 10%, and propane (С3Н8), with a boiling point of – 44o F, up to 3%. Butane (С4Н10), pentane (С4Н12), hexane and octane may be present.

Nearly all natural gas is inflammable. It has no distinct odour. Its main use is for fuel, but it is also used to make carbon black, natural gasoline, liquefied petroleum gas, and certain chemicals.

A method has been perfected to change methane into liquid form.

PETROLEUM

Petroleum is a complex mixture of hydrocarbons. It contains small amounts of oxygen, nitrogen, and sulphur compounds, and traces of metal salts. Hundreds of compounds of varying composition, molecular weight, and structure have been identified. Their properties are extremely varied: some boil below room temperature, some cannot be distilled without decomposition; all are combustible. Many special products come from petroleum: lubricants, waxes, solvents, asphalts for roads, medicinal oils, and numberless chemical derivatives. But the tremendous growth of the petroleum industry has been based on demand for fuels: gasoline, diesel oil, house heating oils for industrial furnaces and steam and power generation.

PETROLEUM PROCESSING

The petroleum refining industry is one of the largest manufacturing industries.

Crude oil is a mixture of many different hydrocarbon compounds, making the chemistry of petroleum refining extremely complex. The refining processes can be grouped under three main headings: (1) separating the crude oils to recover the desired products; (2) breaking the remaining large chemical compounds into smaller chemical compounds by cracking; (3) building the desired chemical compounds by chemical reactions, such as polymerization, reforming, isomerization, etc.

Refinery products, such as gasoline, kerosine, diesel oil, and others, are not pure chemical compounds but mixtures of chemical compounds.

 

6 PERIODIC LAW

 

One of the cornerstone of modern chemical theory is the Periodic Law. It can be simply stated as follows: The properties of the elements are a periodic function of the nuclear charges of their atoms.

In 1869 Mendeleyev arrived at the conclusion that by the arrangement of the elements in order of increasing atomic weight the similarity and periodicity of properties of various, valence groups of the elements were clearly delineated.

There were several vacant spaces in Mendeleyev’s table which led him to predict the existence of six undiscovered elements, (scandium, gallium, germanium, polonium etc.). His confidence in the new classification was clearly expressed in the predictions which he made of the chemical properties of these missing elements. And within fifteen years gallium, scandium and germanium were discovered.

Although this table has been modified hundreds of times, it has withstood the onslaught of all new facts. Isotopes, rare gases, atomic numbers, and electron configurations have only strengthened the idea of the periodicity of the properties of the elements.

 

7 SOME PHYSICAL METHODS USED IN GAS ANALYSIS

 

The relative proportions of various components of gas mixtures can be determined by merely measuring some physical constants of the mixture: the density, the viscosity, the thermal conductivity, heat of combustion, ionization potential.

Condensation methods are often applicable in the separation of complex mixtures of gases. This method has been applied to the gases of the argon group and of natural gas mixtures.

The application of the methods of mass spectrometry to gas analysis has been extensive. The use of a mass spectrometer in analysis enables one to determine the components of mixtures of hydrocarbons, fuel gases, rare gases, etc.

Thermal conductivity applied to gas analysis is rapid, simple to carry out and adaptable to continuous operation and process control.

Some attempts to apply the methods of emission and absorption spectroscopy to gas analysis have been made.

Other miscellaneous methods include magnetic susceptibility, micro-wave analysis, acoustical method based on the principle that the velocity of sound in a gas is a function of the molecular weight of the gas, interferometric methods, diffusion methods and others.

 

8 INORGANIC MOLECULES AND COMPOUNDS

 

Simple diatomic molecules of a single element are designated by the symbol for the element with a subscript 2, indicating that it contains 2 atoms. Thus the hydrogen molecule is H2; the nitrogen molecule, N2; and the oxygen molecule, O2. Polyatomic molecules of a single element are designated by the symbol for the element with a numerical subscript corresponding to the number of atoms in the molecule. Examples are the phosphorus molecule, P4, and the sulphur molecule, S8.

Diatomic covalent molecules, containing unlike elements are given similar designation. The formula for hydrogen chloride is HCl. The more electropositive element is always designated first in the formula.

For polyatomic covalent molecules containing unlike elements, numerical subscriptions are used to designate number of atoms of each element present in the molecule, for example, water, H2O. Again as in diatomic molecules, more electropositive element is placed first in the formula.

 

9 FIELDS OF CHEMISTRY

 

 

The field of chemistry is now a very large one. There are more than 30 different branches of chemistry. Some of the better known fields are inorganic chemistry, organic chemistry, physical chemistry, analytical chemistry, biological chemistry, pharmaceutical chemistry, nuclear chemistry, industrial chemistry, colloidal chemistry, and electrochemistry.

Inorganic chemistry. It is originally considered that the field of inorganic chemistry consists of the study of materials not derived from living organisms. However it now includes all substances other than the hydrocarbons and their derivatives.

Organic chemistry. At one time it was thought that all substances found in plants and animals could be made only by using part of a living plant or animal. The study of these substances, most of which contain carbon was therefore called organic chemistry. It is now known that this idea is quite wrong, for in 1828 F. Wohler made an “organic” substance using a simple laboratory process. Organic chemistry now merely means the chemistry of carbon compounds.

 

 

10 FIELDS OF CHEMISTRY

 

 

The field of chemistry is now a very large one. There are more than 30 different branches of chemistry. Some of the better known fields are inorganic chemistry, organic chemistry, physical chemistry, analytical chemistry, biological chemistry, pharmaceutical chemistry, nuclear chemistry, industrial chemistry, colloidal chemistry, and electrochemistry.

Physical chemistry is concerned with those parts of chemistry which are closely linked with physics as, for instance, the behaviour of substances when a current of electricity is passed through them.

Electrochemistry is concerned with the relation between electrical energy and chemical change. Electrolysis is the process whereby electrical energy causes a chemical change in the conducting medium, which usually is a solution or a molten substance. The process is generally used as a method of deposition metals from a solution.

 

4. Список вопросов к зачету

 

1. Укажите вопросительную и отрицательную формы глаголов “to be”, “to have”.

2. Проспрягайте глагол “to be” в настоящем простом времени.

3. Назовите способы образования сравнительной и превосходной степеней прилагательных.

4. Назовите способы образования множественного числа имен существительных.

5. Назовите несколько личных и притяжательных местоимений.

6. Какие модальные глаголы есть в английском языке, и что они выражают?

7. Какие видовременные формы английского глагола вы знаете?

8. Назовите признаки, по которым можно определить виды английского глагол.

9. Назовите, какое действие обозначает группаIndefinite.

10. Назовите, какое действие обозначает группа Continuous.

11. Назовите, какое действие обозначает группа Perfect.

12. Назовите этапы работы над полным письменным переводом профессионально- ориентированного текста.

 





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