The specific gravity of crude petroleum appears to range from 771 to 1.06, and the flash point from below o° to 370°F.
To illuminating oil or kerosene a series of tests is applied in order that the colour, odour, specific gravity and flash-point or fire-test may be recorded.
In the testing of mineral lubricating oils the viscosity, flash-point, cold-test," and specific gravity are the characters of chief importance.
The first temperature is known as the flash-point, the second as the " fire-test."
It has been found that variations in barometric pressure affect the flash-point and accordingly corrections have to be made in obtaining strictly comparative results at different pressures.