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The straight-chain isomer n-heptane is the zero point of the octane rating scale. It is undesirable in petrol, as it burns explosively, causing engine knocking, as opposed to branched-chain octane isomers, which burn more slowly and give better performance. Its choice for the zero point of the scale was due to the availability of very high purity n-heptane, unmixed with other isomers of heptane or other alkanes, distilled from the resin of Jeffrey Pine. Other sources of heptane and octane, produced from crude oil, contain a mixture of different isomers with greatly differing ratings, so do not give a precise zero point.
Heptane, as well as its many isomers, are widely applied in laboratories as a totally non-polar solvent. Being a liquid, it is ideal for transport and storage. In the grease spot test, heptane is used to dissolve the oil spot to show the previous presence of organic compounds on a stained paper. This is done by shaking the stained paper in a heptane solution for about half a minute.
Heptane is also used as a medium to distinguish bromine from iodine from aqueous mixtures. While both bromine and iodine appear brown in aqueous media, bromine remains brown when dissolved in heptane, while iodine turns purple when mixed with heptane.
Heptane is commercially available as the rubber cement solvent Bestine.
|This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Heptane". A list of authors is available in Wikipedia.|