Aniline Point

Aniline point of an oil is the lowest temperature at which the oil is completely miscible with an equal volume of aniline. Aniline point gives an indication of the deterioration of an oil. When it comes into contact with rubber sealing, packing etc. Generally aromatic hydrocarbons have a tendency to dissolve natural or synthetic rubbers. A higher aniline point less solvent effect on rubber packing, sealing, etc. So a higher aniline point is therefore desirable.

Aniline point is determined by mixing mechanically equal volumes of an oil and aniline in a tube. The mixture is heated until a homogeneous solution is formed. The tube is then allowed to cool at a controlled rate. The temperature at which the two phases separate is noted as the aniline point.