GB/T 7304-2014 in English

《GB/T 7304-2014石油产品酸值的测定 电位滴定法》由TC280（全国石油产品和润滑剂标准化技术委员会）归口，TC280SC1（全国石油产品和润滑剂标准化技术委员会石油燃料和润滑剂分会）执行，主管部门为国家标准化管理委员会。
本标准规定了用电位滴定法测定石油产品、润滑剂、生物柴油以及生物柴油调合燃料酸值的两种测定方法。
方法A 适用于能够溶解和基本溶解于甲苯和无水异丙醇混合溶剂中的石油产品和润滑剂的酸值的测定。方法A 可测定样品中那些在水中离解常数大于1×10-9的酸性组分,离解常数小于1×10-9的极弱酸不产生干扰,但水解常数大于1×10-9的盐类将会参与反应,方法A 的精密度是在酸值(以
KOH 计)为0.1mg/g~150mg/g的范围内建立的。
方法B适用于具有较低酸性和溶解性差异较大的生物柴油和生物柴油调合燃料的酸值的测定。
注:新油或用过油中酸性组分包括有机酸、无机酸、酯类、酚类化合物、内酯、树脂以及重金属盐类、铵盐和其他弱碱
的盐类、多元酸的酸式盐和某些抗氧剂及清净添加剂。
本标准可在不考虑颜色和其他性能变化的前提下反映油品使用过程中在氧化条件下发生的相对变
化。尽管滴定是在特定条件下进行的,但本标准不能用于测定油品的绝对酸性来预测其使用状态下的
性能,没有发现酸值和轴承腐蚀之间有必然的联系。
注1:用本标准测得的酸值结果和用GB/T4945和SH/T0163所测得的结果可能相同也可能不同。本标准中没有尝试将测定结果和其他非滴定方式得到的测定结果进行相关联。
注2:有少数实验室观察到,当在本标准中使用水性或非水性缓冲溶液时,所得到的结果之间有一定的差异。

This standard specifies two test methods for the determination of acidic constituents in petroleum products, lubricants, biodiesel and blends of biodiesel.
Test Method A is applicable to petroleum products and lubricants soluble or nearly soluble in mixtures of toluene 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. Salts react if their hydrolysis constants are larger than 10-9. The range of acid numbers included in the precision statement is 0.1 mg/g KOH to 150mg/g KOH.
Test Method B is applicable to determination of acid number of biodiesel and biodiesel blends with low acidity and greatly different solubility.
Note: In new and used oils, the constituents that may be considered to have acidic characteristics include organic and inorganic acids, esters, phenolic compounds, lactones, resins, salts of heavy metals, salts of ammonia and other weak bases, acid salts of polybasic acids, and addition agents such as inhibitors and detergents.
This standard may be used to indicate relative changes that occur in oil during use under oxidizing conditions regardless of the color or other properties of the resulting oil. Although the titration is made under definite equilibrium conditions, this standard is not intended to measure an absolute acidic property that can be used to predict performance of oil under service conditions. No general relationship between bearing corrosion and acid number is known.
Note 1: The acid number obtained by this standard may or may not be numerically the same as that obtained in accordance with GB/T 4945 and SH/T 0163. There has not been any attempt to correlate this method with other non-titration methods.
Note 2: A few laboratories have made the observation that there is a difference in the standard results when aqueous versus nonaqueous buffers are used.

1. Scope
2. Normative References
3. Terms and Definitions
4. Summary of Test Method
5. Methods and Use
6. Apparatus
7. Reagents
8. Electrode System
9. Standardization of Apparatus
10. Preparation of Sample of Used Oil
11. Test Method A
12. Test Method B
Appendix A (Informative) Check for Electrode Performance
Appendix B (Informative) Determination of Acid Number of Synthetic Oil