1.1 Four methods are prescribed for the determination of acidity of used and unused lubricating oils, liquid fuel oils and petrolatum. Of these, two are for total acidity and one each for inorganic and organic acidities. Oils containing additives may give erroneous results with these methods.
1.2 Methods A and B are suitable for the determination of total acidity. Method A is more suitable than Method B for dark-coloured oils and oils of viscosity higher than 120 cS at 37.8°C and petrolatums. Method B is often preferred for pale-coloured, low viscosity oils. If there is elemental sulphur, only Method A shall be used as Method B may give rise to erroneous results due to interference with the indicator. In any case, Method A shall be used in case of dispute.
1.3 Methods C and D are suitable for the determination of inorganic and 'organic acidities respectively.