Cochin laboratory

API GRAVITY, Degrees

= 141.5 - 131.5

Relative density at 15.6/15.6 deg. C
DIESEL INDEX

The diesel is an indication of ignition quality of diesel fuel, higher the diesel index better is the ignition quality. The diesel index is derived from the API gravity and aniline point the lowest temperature at which the fuel is completely miscible with an equal volume of aniline:

Diesel index = aniline point (°F) x API gravity/100

The above equation is seldom used because the results can be misleading, especially when applied to blended fuels.

DISTILLATION (P 18, D 86, IP 123, ISO 3405)

Distillation characteristics of hydrocarbons have an important effect on safety and performance, especially in the case of fuels and solvents. The boiling range gives information on the composition, the properties, and the behavior of fuels during storage and use. Volatility is the major determinant of the tendency of a hydrocarbon mixture to produce potentially explosive vapors. The distillation characteristics are critically important for both aviation and automotive gasolines, affecting starting, warm-up, and tendency to vapor lock at high operating temperatures or at high altitude, or both. The presence of high boiling components in these and other fuels can significantly affect the degree of formation of solid combustion deposits. Distillation limits are often included in petroleum product specifications, in commercial contract agreements, process refinery/control applications, and for regulatory compliance.