GB/T 4945-2002: Standard test method for acid and base number of petroleum products and lubricants by colour-indicator titration

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Scope

1.1 This Standard is applicable to the determination of acid or basic constituents in
petroleum products and lubricants soluble or nearly-soluble in mixtures of toluene and
isopropyl alcohol. It is applicable for the determination of acids or bases whose
dissociation constants in water are larger than 10−9; extremely weak acids or bases
whose dissociation constants are smaller than 10−9. If their hydrolysis constants are
larger than 10−9, then there is influence.
Notes.
1 In new and used oils, the constituents considered to have acidic characteristics include organic and inorganic
acids, esters, phenolic compounds, lactones, resins, salts of heavy metals, and addition agents such as
inhibitors and detergents. Similarly, constituents considered to have basic properties include organic and
inorganic bases, amino compounds, salts of weak acids (soaps), basic salts of poly acidic bases, salts of
heavy metals, and addition agents such as inhibitors and detergents.
2 This test method is not suitable for measuring the basic constituents of many basic additive-type lubricating oils.
Test method in SH/T 0688 may be used for this purpose.
1.2 This test method can be used to indicate relative changes that occur in an oil
product during use under oxidizing conditions. Although the titration is made under
specified conditions, the method is not able to measure an absolute acidic or basic
property that may be used to predict performance of an oil product under service
conditions. No general relationship between bearing corrosion and acid or base
numbers is known.
Note. Oils, such as many cutting oils, rust proofing oils, and similar compounded oils, or dark-colored oils, that are
not able to be analyzed for acid number by this test method due to obscurity of the color-indicator end point,
may be analyzed by test method in GB/T 7304. The acid numbers obtained by this color-indicator test
method need not be numerically the same as those obtained by test method in GB/T 7304, the base
numbers obtained by this color indicator test method need not be numerically the same as those obtained by
test method in SH/T 0688, but their data is in a certain relation.

Basic Data

Standard ID	GB/T 4945-2002 (GB/T4945-2002)
Description (Translated English)	Standard test method for acid and base number of petroleum products and lubricants by colour-indicator titration
Sector / Industry	National Standard (Recommended)
Classification of Chinese Standard	E30
Classification of International Standard	75.08
Word Count Estimation	12,170
Date of Issue	1/14/2002
Date of Implementation	8/1/2002
Older Standard (superseded by this standard)	GB/T 4945-1985 (1991)
Quoted Standard	GB/T 6682; GB/T 7304; SH/T 0688
Adopted Standard	ASTM D974-1997, MOD
Issuing agency(ies)	General Administration of Quality Supervision, Inspection and Quarantine of the People Republic of China
Summary	This Standard is applicable to the determination can be dissolved in a mixed solvent full or almost full dissolution of acidic or alkaline components of petroleum products and lubricants in toluene and isopropanol. It is suitable for measuring the water dissociation constant greater than 10-9 acid or very weak acid or base dissociation constant of less than 10-9 does not affect the determination, if the salt hydrolysis constant is greater than 10-9, the influential.