Octane rating scale n-Heptane is defined as the zero point of the octane rating scale. It is a lighter component in gasoline and burns more explosively, causing engine pre-ignition (knocking) in its pure form, as opposed to octane isomers, which burn more slowly and give less knocking. It was originally chosen as the zero point of the scale because of the availability of very high purity n-heptane, unmixed with other isomers of heptane or other alkanes, distilled from the resin of Jeffrey pine and from the fruit of Pittosporum resiniferum. Other sources of heptane and octane, produced from crude oil, contain a mixture of different isomers with greatly differing ratings, and do not give as precise a zero point.
Octane rating scale n-Heptane is defined as the zero point of the octane rating scale. It is a lighter component in gasoline and burns more explosively, causing engine pre-ignition (knocking) in its pure form as opposed to octane isomers, which burn more slowly and give less knocking. It was ori,ginally chosen as the zero point of the scale because of the availability of very high purity n-heptane, unmixed with other isomers of heptane or other alkanes, distilled from the resin of Jeffrey pine and from the fruit of Pittosporum resiniferum. Other sources of heptane and octane, produced from crude oil, contain a mixture of different isomers with greatly differing ratings, and do not give as precise a zero point.