Aniline point

The aniline point of an oil is defined as the minimum temperature at which equal volumes of aniline (C
6H
5NH
2) and the oil are miscible, i.e. form a single phase upon mixing.

The value gives an approximation for the content of aromatic compounds in the oil, since the miscibility of aniline, which is also an aromatic compound suggests the presence of similar (i.e. aromatic) compounds in the oil. The lower the aniline point, the greater is the content of aromatic compounds in the oil as obviously a lower temperature is needed to ensure miscibility.