PHYSICAL PROPERTIES OF HYDROCARBONS

Petroleum is formed under the earth s surface by the decomposition of organic material. The remains of tiny organisms that lived in the sea and, to a lesser extent, those of land organisms were carried down to the sea in rivers along with plants that grow on the ocean bottoms combined with the fine sands and silts in calm sea basins. These deposits, which are rich in organic materials, become the source rocks for the formation of carbon and hydrogen, i.e., natural gas and crude oil. 

This process began many millions of years ago with the development of abundant life, and it continues to this day. The sediments grow thicker and sink into the sea floor under their own weight. As additional deposits pile up, the pressure on the ones below increases several thousand times, and the temperature rises by several hundred degrees. The mud and sand harden into shale and sandstone. Carbonate precipitates and skeletal shells harden into limestone. The remains of the dead organisms are then transformed into crude oil and natural gas. Usually the underground and formation pressure is sufficient for the natural release of hydrocarbon liquids and gases to the surface of the earth. 

Natural petroleum is distilled and reformulated to produce a variety of fuels for general use and as raw 

Three broad classes of crude petroleum exist the paraffin types, the asphaltic types, and the mixed-base types. The paraffin types are composed of molecules in which the number of hydrogen atoms is always two more than twice the number of carbon atoms. The characteristic molecules in the asphaltic types are naphthenes, composed of twice as many hydrogen atoms as carbon atoms. In the mixed-base group are both paraffin hydrocarbons and naphthenes. 

The saturated open-chain hydrocarbons form a homologous series called the paraffin series or the alkane series. The composition of each of the members of the series corresponds to the formula CnH2n + 2 where n is the number of carbon atoms in the molecule. All the members of the series are unreactive. They do not react readily at ordinary temperatures with such reagents as acids, alkalies, or oxidizers. 

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The physical properties of hydrocarbon fluids General hydrocarbon phase behaviour... 

R. W. Gallant, Physical Properties of Hydrocarbons, Gulf Pubhshing Co., Houston, Tex., 1968. 

Table 5 Some physical properties of hydrocarbon salts prepared from Kuhn s anion [2... 

Gallant, R.W. Physical Properties of Hydrocarbons, vol. 1 2, Gulf, Houston, 1968. 

The following year Ricardo 27) published the results of investigations on the highest useful compression ratio of a number of hydrocarbons and found a wide variation among different fuels in this respect. Since that time the relations between physical properties of hydrocarbons and their molecular structure on the one hand, and the knocking characteristics of the same hydrocarbons and their molecular structure on the other, have received more intensive study. 

What physical property of hydrocarbons is used in fractional distillation ... 

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