This document provides information on the composition of crude oil. It discusses that crude oil is a mixture of hydrocarbons that is liquid underground but varies in color from yellow to black. It is composed primarily of carbon and hydrogen. The main components are paraffins, naphthenes, and aromatics. Crude oil also contains smaller amounts of other elements and compounds like sulfur. The document also describes different methods of classifying crude oils based on their chemical composition and geological parameters.