ISO 3771:2011规定了在冰醋酸中用高氯酸电位滴定法测定石油产品中碱性成分的方法。 可以认为具有碱性特征的组分包括有机和无机碱、氨基化合物、弱酸盐(例如皂)、多元酸碱的碱性盐和重金属盐。 已建立该方法精密度值的基数值范围为: 未使用的油:碱值从3到45； 添加剂浓缩物:碱值为5至45； 废油:基数从3到30。

ISO 3771:2011 specifies a method for the determination of basic constituents in petroleum products by potentiometric titration with perchloric acid in glacial acetic acid. The constituents that can be considered to have basic characteristics include organic and inorganic bases, amino compounds, salts of weak acids (e.g. soaps), basic salts of polyacid bases, and salts of heavy metals. The ranges of base number values for which precision values for the method have been established are:

• unused oils: base numbers from 3 to 45;
• additive concentrates: base numbers from 5 to 45;
• used oils: base numbers from 3 to 30.