1.1 本试验方法包括测定原油和石油产品中的酸性成分，包括可溶于二甲苯和丙-2-醇混合物的蜡、沥青、基础油和沥青。适用于水中离解常数大于10的酸的测定 –9 ; 离解常数小于10的极弱酸 –9 不要干涉。通过该试验方法获得的值在数值上可能与其他酸值测量值不相等。精密度声明中包含的KOH酸值范围为0.1 mg/g至16 毫克/克。 1.2 以国际单位制表示的数值应视为标准。本标准不包括其他计量单位。 1.3 本标准并非旨在解决与其使用相关的所有安全问题（如有）。 本标准的使用者有责任在使用前制定适当的安全、健康和环境实践，并确定监管限制的适用性。 第节中给出了一些具体的危险说明 7. 关于安全预防措施。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认的标准化原则制定的。 ====意义和用途====== 5.1 原油和油砂沥青含有天然存在的酸性物质。原油的酸性与分配系统和工艺系统的腐蚀有关。这些物质的相对量可以通过用碱滴定来确定。 酸值是在测试条件下测量油中酸性物质的量。 5.2 通过试验方法测量了原油和蒸馏石油馏分的酸值 D664型 .试验方法 D664型 用于分析润滑剂和生物柴油。试验方法中使用的滴定溶剂 D664型 未能正确处理本试验方法中涉及的溶解困难样品，如原油、沥青和高蜡样品。提到 附录X1 . 5.3 试验方法 第974页 也不适用于测量原油和高颜色样品的酸度，因为指示剂不可见或难以辨别颜色变化以检测滴定终点。

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, health, and environmental 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. ====== 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.