GB/T 4945-2002 English PDF (GBT4945-2002)

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GB/T 4945-2002: Standard test method for acid and base number of petroleum products and lubricants by colour-indicator titration
GB/T 4945-2002
GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 75.080
E 30
Standard Test Method for Acid and Base Number
of Petroleum Products and Lubricants by
Colour-indicator Titration
ISSUED ON. JANUARY 14, 2002
IMPLEMENTED ON. AUGUST 01, 2002
Issued by. General Administration of Quality Supervision, Inspection
and Quarantine of the People’s Republic of China
Table of Contents
Foreword ... 3 
1 Scope ... 4 
2 Normative References ... 4 
3 Definitions ... 5 
4 Summary of Test Method ... 5 
5 Significance and Use ... 6 
6 Apparatus ... 6 
7 Reagents ... 6 
8 Test Preparation ... 7 
9 Procedure for Determining Acid Number ... 9 
10 Procedure for Base Number ... 10 
11 Procedure for Determining Strong Acid Number ... 10 
12 Quality Control Checks ... 11 
13 Calculation ... 11 
14 Precision and Deviation ... 13 
15 Report ... 14 
Annex A (Normative) Specifications for P-naphtholbenzein ... 15 
Foreword
This Standard equivalently adopts American Society for Testing and Materials ASTM
D974-1997 "Standard Test Method for Acid and Base Number by Color-Indicator
Titration". It is a revision to GB/T 4945-1985 (1991) "Petroleum Products and
Lubricants-Neutralization Number-Colour Indicator Titration Method".
The differences between this Standard and ASTM D 974-1997 are as follows.
1. The standard names are different. The name of ASTM D974-1997 is "Standard
Test Method for Acid and Base Number by Color-Indicator Titration"; while the
name of this Standard is "Standard Test Method for Acid and Base Number of
Petroleum Products and Lubricants by Colour-indicator Titration".
The main revision in this Standard to GB/T 4945-1985 (1991).
1. The standard name was revised from "Petroleum Products and Lubricants -
Neutralization Number - Colour Indicator Titration Method" to "Standard Test
Method for Acid and Base Number of Petroleum Products and Lubricants by
Colour-indicator Titration".
2. The total acid number was revised to acid number.
3. For the preparation of standard solution of potassium hydroxide-isopropanol,
the sample weight of potassium hydroxide was revised from 5.6g to 6g;
preparation process has some difference.
Annex A in this Standard is normative.
This Standard was proposed by the State Bureau of Petroleum and Chemical
Industry.
This Standard shall be under the jurisdiction of Sinopec Research Institute of
Petroleum Processing.
Drafting organization of this Standard. Lanzhou Lubricating Oil Research and
Development Institute of Petro China.
Chief drafting staffs of this Standard. Li Suping, Zhou Yabin, and Gao Jun.
This Standard was issued in 1985 for the first time.
Standard Test Method for Acid and Base Number of
Petroleum Products and Lubricants by
Colour-indicator Titration
1 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.
2 Normative References
The following standards contain provisions which, through reference in this text,
constitute provisions of this Standard. Unless otherwise specified in the standard, the
standards below shall be valid and current.
GB/T 6682 Water for Analytical Laboratory Use - Specification and Test Methods
GB/T 7304 Petroleum Products and Lubricants - Determination of Neutralization
Number - Potentiometric Titration Method
SH/T 0688 Petroleum Products and Lubricants - Determination of Base Number -
Potentiometric Titration Method
3 Definitions
This Standard adopts the definitions as follows.
3.1 Acid number
It refers to the quantity of base of sample that is required to titrate a sample of 1g to a
specified end point, expressed in mgKOH/g.
3.2 Base number
It refers to the quantity of acid of sample that is required to titrate a sample of 1g to a
specified end point, expressed in mgKOH/g.
3.3 Strong acid number
It refers to the quantity of base of sample that is required to titrate a hot water extract
of 1g sample to a yellow end point using methyl orange solution, expressed in
mgKOH/g.
3.4 Used oil
It refers to any oil that has been in a part of equipment (for example, an engine,
gearbox, transformer, or turbine) whether operated or not.
4 Summary of Test Method
4.1 To determine the acid or base number, the sample shall be dissolved in a
mixture of toluene and isopropyl alcohol containing a small amount of water, and the
resulting single-phase solution shall be titrated at room temperature with standard
alcoholic base or alcoholic acid solution, respectively, to the end point indicated by the
color change of the added p-naphtholbenzein solution (orange in acid and dark green
in base). To determine the strong acid number, a separate portion of the sample is
extracted with hot water and the aqueous extract shall be titrated with potassium
7.4 Distilled water. it shall be adopted in accordance with the specification of Type III
in GB/T 6682.
7.5 Potassium hydrogen phthalate solution. standard reagent.
7.6 Barium hydroxide solution. analytical reagent.
7.7 Methylbenzene solution. analytical reagent.
8 Test Preparation
8.1 Preparation of solution and solvent
8.1.1 Hydrochloric acid and isopropanol standard solution (0.1mol/L)
Mix 9mL of hydrochloric acid solution (note 1) with 1000mL of isopropyl alcohol,
accurately take 8mL of 0.1mol/L potassium hydroxide - isopropanol standard soluti...