Octane number - Characteristics of hydrocarbons
It is utilized for measuring the knocking character of fuel utilized in petrol engine. The octane quantity of an offered sample can be defined as the percentage by volume of iso-octane present in a mixture of iso-octane and n-heptane that has similar knocking performance as the fuel itself.
CH3 - CH2 - CH2 - CH2 - CH2 - CH2 - CH3
n-heptane; octane no. = 0