ASTM D5770 Test Method for Semiquantitative Micro Determination of Acid Number of Lubricating Oils During Oxidation Testing
1. Scope
1.1 This test method is a semiquantitative micro method intended for monitoring the changes in acidic constituents occurring in lubricating oils during oxidation testing, when the acid number of such oils falls within the range from 0.02 mg to 1.0 mg of potassium hydroxide per gram of sample. It is applicable to such oils as turbine oils, hydraulic oils, and other circulating oils.
NOTE 1 - This test method is a micro version of Test Method D974 and it produces results similar to that method.
1.2 This test method is designed for use where sample size is limited. It shall not be used as a replacement for higher precision methods such as Test Methods D974 or D664. It shall not be used to monitor oils in-service.
1.3 The values stated in SI units are to be regarded as the standard.
1.3.1 Exception - The values given in parentheses are for information only.
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 and health 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 issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D664 Test Method for Acid Number of Petroleum Products by Potentiometric Titration
D943 Test Method for Oxidation Characteristics ofInhibited Mineral Oils
D974 Test Method for Acid and Base Number by Color-Indicator Titration
D3339 Test Method forAcid Number of Petroleum Products by Semi-Micro Color Indicator Titration
D4871 Guide for Universal Oxidation/Thermal Stability Test Apparatus
3. Terminology
3.1 Definitions:
3.1.1 acid number, n - the quantity of a specified base, expressed in milligrams of potassium hydroxide per gram of sample, required to titrate a sample in a specified solvent to a specified endpoint using a specified detection system.
3.1.1.1 Discussion - In this test method, the acid number is calculated from the number of drops required to produce a change in solution color from blue-green to orange, compared to the number of drops required to produce an identical color change using a reference standard. Because this is a direct comparison method, the acid number value can be reported in milligrams of potassium hydroxide per gram of sample.
