Petroleum ether, also known as benzine, VM&P naphtha (varnish makers' & painters'), petroleum naphtha, naphtha ASTM, petroleum spirits, X4 or ligroin, is a group of various volatile, highly flammable, liquid hydrocarbon mixtures used chiefly as nonpolar solvents. Chemically, it is not an ether like diethyl ether, but a light hydrocarbon.
Petroleum ether is obtained from petroleum refineries as the portion of the distillate which is intermediate between the lighter naphtha and the heavier kerosene. It has a specific gravity of between 0.6 and 0.8 depending on its composition. The following distillation fractions of petroleum ether are commonly available: 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, despite its synonym of benzine, should not be confused with benzene or benzyne, nor should it be confused with gasoline although many languages and dialects call that with a name derived from benzine, e.g. "Benzin" (German), "benzine" (Dutch), "benzina" (Italian), "bencina" (Chilean Spanish), or "benzină" (Romanian). 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 is useful for removing the gum from self-adhesive stamps. It is the main ingredient of some 'label remover' or 'sticker remover' products.
Ligroin is a refined saturated hydrocarbon petroleum fraction similar to petroleum ether used mainly as a laboratory solvent. It 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.
The first motor car, the Benz Patent-Motorwagen, used ligroin as a fuel.
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