ASTM D8045 - 17

    Standard Test Method for Acid Number of Crude Oils and Petroleum Products by Catalytic Thermometric Titration

    Active Standard ASTM D8045 | Developed by Subcommittee: D02.06

    Book of Standards Volume: 05.05

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    Significance and Use

    5.1 Crude oils and oil sands bitumen contain naturally occurring acidic species. Acidity of crude oil has been implicated in corrosion of distribution and process systems. The relative amount of these materials can be determined by titrating with bases. The acid number is a measure of this amount of acidic substance in the oil under the conditions of the test.

    5.2 Acid number of crude and distilled petroleum fractions has been measured by Test Method D664. Test Method D664 was developed for the analysis of lubricants and biodiesel. The titration solvent used in Test Method D664 does not properly address dissolving difficult samples such as crude oil, bitumen, and high wax samples addressed in this test method. Refer to Appendix X1.

    5.3 Test Method D974 is also not applicable to measuring acidity of crudes and highly colored samples because the indicator is not visible or it is difficult to discern a color change to detect the end point of the titration.

    1. Scope

    1.1 This test method covers the determination of acidic components in crude oil and petroleum products including waxes, bitumen, base stocks, and asphalts that are soluble in mixtures of xylenes and propan-2-ol. It is applicable for the determination of acids whose dissociation constants in water are larger than 10–9; extremely weak acids whose dissociation constants are smaller than 10–9 do not interfere. The values obtained by this test method may not be numerically equivalent to other acid value measurements. The range of KOH acid numbers included in the precision statement is 0.1 mg/g to 16 mg/g.

    1.2 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

    1.3 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. Some specific hazards statements are given in Section 7 on Safety Precautions.

    1.4 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 (purchase separately) The documents listed below are referenced within the subject standard but are not provided as part of the standard.

    ASTM Standards

    D664 Test Method for Acid Number of Petroleum Products by Potentiometric Titration

    D974 Test Method for Acid and Base Number by Color-Indicator Titration

    D1193 Specification for Reagent Water

    D4057 Practice for Manual Sampling of Petroleum and Petroleum Products

    D4175 Terminology Relating to Petroleum Products, Liquid Fuels, and Lubricants

    D4177 Practice for Automatic Sampling of Petroleum and Petroleum Products

    D5854 Practice for Mixing and Handling of Liquid Samples of Petroleum and Petroleum Products

    D6299 Practice for Applying Statistical Quality Assurance and Control Charting Techniques to Evaluate Analytical Measurement System Performance

    ICS Code

    ICS Number Code 75.040 (Crude petroleum); 75.080 (Petroleum products in general)

    UNSPSC Code

    UNSPSC Code 15101500(Petroleum and distillates)

    Referencing This Standard
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    DOI: 10.1520/D8045-17

    Citation Format

    ASTM D8045-17, Standard Test Method for Acid Number of Crude Oils and Petroleum Products by Catalytic Thermometric Titration, ASTM International, West Conshohocken, PA, 2017,

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