Heptane is a colorless and volatile liquid, often used as a standard for octane number determination, a solvent, and used in organic synthesis and the preparation of experimental reagents.

　　The nature of the solvent oil varies according to its purpose. The choice of the solvent oil should mainly consider its solubility, volatility and safety. Of course, depending on its use, other properties cannot be ignored, and sometimes even more important.

　　Solvent oil includes two processes: cutting and refining. The process of cutting fractions usually has the following three methods: direct extraction from an atmospheric tower; cutting the corresponding light straight-run fractions into appropriate narrow fractions; and fractionating the catalytic reforming raffinate. Various solvent oil fractions generally need to be refined. In order to improve color, improve stability, remove corrosive substances and reduce toxicity. Commonly used refining methods include alkaline washing, white clay refining and hydrorefining.

　　Solvent oil is a complex mixture of hydrocarbons and is extremely flammable and explosive. Therefore, from production, storage and use, strict attention must be paid to preventing fires.

　　Solvent oil toxicity can be expressed in three ways:

　　Lethal dose (LD): Generally used to indicate the intensity of highly toxic substances on the physiological effects of animals.

　　Lethal concentration (LC): A measure of acute poisoning by concentration.

　　Large allowable concentration (MAC): The large allowable concentration is usually expressed in parts per million (ppm or 10-6) of the vapor capacity in the air. This is a rough estimate of solvent toxicity, which varies from person to person and is not an absolute limit.