Crude Oil – is extracted from the earth through oil wells. Color of crude oil is usually black, but sometimes the color may vary, for example, it can be yellowish or slightly transparent – all of these properties depend on the ratio of carbohydrates in the crude oil.
The structure consists of a complex mixture of organic matter and carbon. Oil Research Institute found more than five hundred of complex chemical constituents.
List of constituent parts, which are part of crude oil:

Carbohydrates – 90%

Oxygen – 0 to 1%

Hydrogen – from 10 to 15%

Sulphur – 0.1 to 3.0%

Nitrogen – from 0.1 to 0.5%

In composition, each grade of crude oil may have a difference somewhere percentage of sulfur or nitrogen will be more. The composition of crude oil can contain special light materials, which tend to evaporate quickly. There are also varieties of oil, which are substances with a weight, such as a substance like bitumen.
Crude oil is divided into several categories depending on the content in the different fractions of oil and its density – kg / cu. m