ASTM D974-22 PDF
Standard Test Method for Acid and Base Number by Color-Indicator Titration
Standard Test Method for Acid and Base Number by Color-Indicator Titration
- Статус документа:
- Действующий
- Формат:
- Электронный (PDF)
- Количество страниц:
- 7
- Дата публикации:
- 1 ноября 2022 г.
- Издание:
- D974
- ICS:
- 75.080
SIGNIFICANCE AND USE 5.1 New and used petroleum products can contain basic or acidic constituents that are present as additives or as degradation products formed during service, such as oxidation products. The relative amount of these materials can be determined by titrating with acids or bases. This number, whether expressed as acid number or base number, is a measure of this amount of acidic or basic substances, respectively, in the oil—always under the conditions of the test. This number is used as a guide in the quality control of lubricating oil formulations. It is also sometimes used as a measure of lubricant degradation in service; however, any condemning limits must be empirically established. 5.2 Since a variety of oxidation products contribute to the acid number and the organic acids vary widely in corrosive properties, the test cannot be used to predict corrosiveness of an oil under service conditions. No general correlation is known between acid number and the corrosive tendency of oils toward metals. Compounded engine oils can and usually do have both acid and base numbers in this test method. SCOPE 1.1 This test method covers the determination of acidic or basic constituents (Note 1) in petroleum products3 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 do not interfere. Salts react if their hydrolysis constants are larger than 10−9. Note 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 polyacidic bases, salts of heavy metals, and addition agents such as inhibitors and detergents. Note 2: This test method is not suitable for measuring the basic constituents of many basic additive-type lubricating oils. Test Method D4739 can be used for this purpose. 1.2 This test method can be used to indicate relative changes that occur in an oil during use under oxidizing conditions. Although the titration is made under definite equilibrium conditions, the method does not measure an absolute acidic or basic property that can be used to predict performance of an oil under service conditions. No general relationship between bearing corrosion and acid or base numbers is known. Note 3: Oils, such as many cutting oils, rustproofing oils, and similar compounded oils, or excessively dark-colored oils, that cannot be analyzed for acid number by this test method due to obscurity of the color-indicator end point, can be analyzed by Test Method D664. The acid numbers obtained by this color-indicator test method need not be numerically the same as those obtained by Test Method D664, the base numbers obtained by this color indicator test method need not be numerically the same as those obtained by Test Method D4739, but they are generally of the same order of magnitude. 1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard. 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.5 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations...
Abstract
Overview
ASTM D974-22 is the internationally recognized Standard Test Method for Acid and Base Number by Color-Indicator Titration, published by ASTM International. This method enables the determination of acidic or basic constituents in petroleum products and lubricants that are soluble or nearly soluble in mixtures of toluene and isopropyl alcohol. The test is commonly used for both new and used oils, playing a critical role in the quality control of lubricating oil formulations and in monitoring lubricant degradation over time.
The acid number obtained via this color-indicator titration reflects the concentration of acidic or basic substances in a given oil sample under the test conditions. Although this test is fundamental in oil analysis, results do not directly predict corrosiveness or performance in service; instead, they indicate relative chemical changes that may occur during oil service life.
Key Topics
- Determination of Acid and Base Number: The method measures acidic and basic constituents, expressed as acid number and base number, based on color change using a p-naphtholbenzein indicator.
- Applicable to Petroleum Products and Lubricants: Suitable for products soluble or nearly soluble in toluene and isopropyl alcohol mixtures.
- Guidance for Quality Control: Acid and base number values support the formulation and monitoring of lubricating oils, ensuring they meet manufacturer and industry specifications.
- Assessment of Oil Degradation: The test tracks the relative increase in acidic products due to oxidation and degradation during oil use.
- Limitations: The test cannot be used to reliably predict oil corrosiveness or the performance of lubricants in service; specific condemnation limits for acid or base numbers must be empirically established.
- Sample Preparation and Accuracy: Proper sampling, homogenization, and avoidance of contamination are critical for precise results, especially when handling used or dark-colored oils.
- Safety and Compliance: Laboratories must adhere to safety, health, and environmental guidelines, and confirm compliance with local regulatory requirements.
Applications
ASTM D974-22 is utilized across a wide range of sectors including:
- Lubricating Oil Quality Control: Used by lubricant manufacturers to monitor base stock purity and the effects of additive treatments.
- In-Service Oil Monitoring: Employed by maintenance and reliability teams in industries such as automotive, marine, power generation, and manufacturing to track lubricant degradation through increased acid numbers.
- Blending and Formulation: Applied in laboratories for checking batch consistency and compliance with product specifications during oil blending.
- Petroleum Product Research: Facilitates the development and testing of new oil formulations where control of acid and base content is essential.
- Used Oil Analysis: Supports asset management and predictive maintenance by identifying oil degradation products that may indicate equipment wear or contamination.
Related Standards
Professionals working with acid and base number titration may also reference the following ASTM standards:
- ASTM D664: Test Method for Acid Number of Petroleum Products by Potentiometric Titration, suited for oils incompatible with the color-indicator detection method.
- ASTM D4739: Test Method for Base Number Determination by Potentiometric Hydrochloric Acid Titration, particularly for oils with strong basic additives.
- ASTM D4057 and D4177: Practices for manual and automatic sampling of petroleum and petroleum products, essential for representative sample preparation.
- ASTM D1193: Specification for Reagent Water, which defines water quality requirements for laboratory analyses.
- ASTM D4175: Terminology relating to petroleum products, liquid fuels, and lubricants, for standardized definitions.
By adhering to ASTM D974-22, organizations can ensure accurate determination of acid and base numbers in petroleum products, supporting quality assurance, regulatory compliance, and extended service life of equipment through effective lubricant management.
Keywords: ASTM D974, acid number, base number, color-indicator titration, petroleum products, lubricants, oil quality control, lubricant degradation, oil analysis.
Технические детали
- Технический комитет
- D02 - Petroleum Products, Liquid Fuels, and Lubricants
- SKU
- ASTM D974-22
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