Petroleum ether is a highly flammable liquid distillate of petroleum heavier than naphtha and lighter than kerosene. Known variously as benzine, varnish makers & painters naphtha (VM&P), petroleum naphtha, naphtha ASTM, and petroleum spirits, it is a lightweight hydrocarbon used chiefly as a nonpolar solvent. Pether, X4, and ligroin (used by the first motor car, the Benz Patent-Motorwagen, as fuel) are related hydrocarbon mixtures.
Petroleum ether is a mixture of alkanes, e.g., pentane, hexane, and heptane, whereas benzene is a cyclic, aromatic hydrocarbon, C6H6. Likewise, petroleum ether should not be confused with the class of organic compounds called ethers, which contain the R-O-R' functional group.
Petroleum ether refined from petroleum as the intermediate distillate between the lighter naphtha and the heavier kerosene. It has a specific gravity of between 0.6 and 0.8 depending on its composition. Distillation fractions of petroleum ether are commonly available as: 30 to 40 °C, 40 to 60 °C, 60 to 80 °C, 80 to 100 °C, 80 to 120 °C, and sometimes 100 to 120 °C. The 60 to 80 °C fraction is often used as a replacement for hexane. Petroleum ether is mostly used by pharmaceutical companies and in the manufacturing process. Petroleum ether consists mainly of pentane, and is sometimes used instead of pentane due to its lower cost.
- Petroleum ether is the main ingredient of some 'label removers'.
- Ligroin, a refined saturated hydrocarbon petroleum fraction similar to petroleum ether, is used mainly as a laboratory solvent. It also served as fuel for the first motor car, the Benz Patent-Motorwagen.
- Ligroin predominantly consists of C7 to C11 in the form of about 55% paraffins, 30% monocycloparaffins, 12% alkylbenzenes, and 2% dicycloparaffins. It is nonpolar. Generally laboratory grade ligroin boils at 60 to 90 °C.
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