IP 449: Petroleum products and lubricants - Determination of acid number - Non-aqueous potentiometric titration method

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  • Method adopted/last revised: 2000
  • Method reapproved: None
  • REF/ISBN: IP449-2934869
  • Status: Current
  • First printed in STM books: January 2000


This European Standard specifies a method for determination of acid number by potentiometric titration, of lubricating oils and additives soluble in mixtures of propan-2-01, dimethylsulfoxide and toluene. It is applicable in the range 0,1 mg KOH/g to 250 mg KOH/g, and to unused and used lubricating oils and additives.
In the case of engine oils, used engine oils and oils with a high polymer content, e.g. viscosity index improvers, precision will be poor as the electrode performance will be impaired, and the application of this method is not recommended. Precision data are only valid for industrial oils and related products.

NOTE No direct conclusions can be drawn from the content of the acidic constituents on the suitability of lubricants for specific applications, and it is not possible to rate comparatively the quality of lubricants and additives on the basis of the quantity of acidic components.

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