Whatever the process used, crude oil must be refined. The complete refining of oil consists of the following operations: • separation of solid impurities that is impurities not soluble in oil, • separation of free water, • partial separation of dissolved moisture that is dehydration or drying, • de-gumming, • separation of free fatty acids or neutralization,  • separation, reduction or destruction of pigments, that is bleaching, and • separation, reduction of destruction of volatile compounds affecting odour or taste that is deodorization.