ISO INTERNATIONAL STANDARD 6619 First edition 1988-12-01 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEXKAYHAPOAHAAOPTAHM3ALMANO CTAHAAPTW3ALMM Petroleum products and lubricants - Neutralization number -- Potentiometric titration method potentiometrique Referencenumber ISO 6619: 1988 (E) orking permitted without license from IHS Not for Resale ISO 6619 : 1988 (E) Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (Iso member bodies). The work of preparing International Standards is normally carried out through iso technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, govern- mental and non-governmental, in liaison with Iso, also take part in the work. IsO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. Draft International Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by least 75 % approval by the member bodies voting International Standard ISO 6619 was prepared by Technical Committee ISO/TC 28, Petroleum products and lubricants. Annex A of this International Standard is for information only. International Organization for Standardization, 1988 Printed in Switzerland ted without license from IHS Not for Resale INTERNATIONAL STANDARD ISO 6619 : 1988 (E) Petroleum products and lubricants - Neutralization number - Potentiometric titration method 1 Scope amount of acidic substances in the oil under the conditions of the test. The acid number is used as a guide in the quality con- trol of lubricating oil formulations. It is also sometimes used as 1.1 This International Standard specifies a method for the a measure of lubricant degradation in service. Any condemning determination of acidic constituents in petroleum products and limits must be empirically established. lubricants soluble or nearly soluble in mixtures of toluene and propan-2-ol. It is applicable for the determination of acids As a variety of oxidation products contribute to the acid whose dissociation constants in water are larger than 10 -9; ex- number and the organic acids vary widely in corrosion proper- tremely weak acids whose dissociation constants are smaller ties, the test cannot be used to predict corrosiveness of an oil than 10-9 do not interfere. Salts react if their hydrolysis con- under service conditions. No general correlation is known be- stants are larger than 10-9. tween acid number and the corrosive tendency of oils toward metals. Compounded engine oils can, and usually do, have an NOTE -- In new and used oils, the constituents that may be considered acid number in this test. to have acidic characteristics include organic and inorganic acids, esters, phenolic compounds, lactones, resins, salts of heavy metals, salts of ammonia and other weak base constituents, acid salts of polybasic acids, and additives such as inhibitors and detergents. 2 Definitions 1.2 This method may be used to indicate relative changes that occur in an oil during use under oxidizing conditions For the purposes of this International Standard, the following regardless of the colour or other properties of the resulting oil. definitions apply. Although the titration is made under definite equilibrium condi- tions, the method does not measure an absolute acidic or basic acid number: The quantity of base, expressed in 2.1 property that can be used to predict performance of an oil 'milligrams of potassium hydroxide per gram of sample, re- under service conditions. No general relationship between quired to titrate potentiometrically a test portion in a specified bearing corrosion and acid or base number is known. solvent from its initial meter readin