ISO 660:2009 specifies three methods (two titrimetric and one potentiometric) for the determination of the acidity in animal and vegetable fats and oils. The acidity is expressed preferably as acid value, or alternatively as acidity calculated conventionally. ISO 660:2009 is applicable to refined and crude vegetable or animal fats and oils, soap stock fatty acids or technical fatty acids. The methods are not applicable to waxes. Since the methods are completely non-specific, they cannot be used to differentiate between mineral acids, free fatty acids, and other organic acids. The acid value, therefore, also includes any mineral acids that may be present.