1.1 本试验方法包括碳分布和环含量的计算( 注1 )根据折射率、密度和分子量（n-d-M）的测量，对不含烯烃的石油进行分析。 2. 本试验方法不适用于成分不在以下范围内的油: 1.1.1 就碳分布而言- 最多75 % 环结构中的碳原子；芳香环中的百分比不大于环烷环中百分比的1.5倍。 1.1.2 就环含量而言- 每个分子最多四个环，其中不超过一半是芳香的。必须对含有大量硫的油进行校正。 注1: 复杂石油馏分的组成通常用芳香环的比例表示( R A. )，环烷环( R N )和石蜡链( C P )其将包括假设的平均分子。或者，该组合物可以用碳分布来表示，即存在于芳香环结构中的碳原子总数的百分比（% C A. )，环烷环结构（% C N )和石蜡链（% C p ). 1.2 以国际单位制表示的数值应视为标准。 1.2.1 例外情况- 括号中的值仅供参考。 1.3 本标准并不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建立适当的安全、健康和环境实践，并确定监管限制的适用性。 1.4 本国际标准是根据世界贸易组织技术性贸易壁垒（TBT）委员会发布的《国际标准、指南和建议制定原则决定》中确立的国际公认标准化原则制定的。 =====意义和用途====== 5.1 碳分布和环含量用来表示石油较重馏分的总组成。 这些数据可作为散装性质的辅助数据，用于监测通过蒸馏、溶剂精炼或氢化或两者同时进行的润滑油基础油的生产，以及比较不同原油来源的原料组成。此外，数据通常可以与关键的产品性能特性相关联。

1.1 This test method covers the calculation of the carbon distribution and ring content ( Note 1 ) of olefin-free petroleum oils from measurements of refractive index, density, and molecular weight (n-d-M). 2 This test method should not be applied to oils whose compositions are outside the following ranges: 1.1.1 In terms of carbon distribution— up to 75 % carbon atoms in ring structure; percentage in aromatic rings not larger than 1.5 times the percentage in naphthenic rings. 1.1.2 In terms of ring content— up to four rings per molecule with not more than half of them aromatic. A correction must be applied for oils containing significant quantities of sulfur. Note 1: The composition of complex petroleum fractions is often expressed in terms of the proportions of aromatic rings ( R A ), naphthene rings ( R N ), and paraffin chains ( C P ) that would comprise a hypothetical mean molecule. Alternatively, the composition may be expressed in terms of a carbon distribution, that is, the percentage of the total number of carbon atoms that are present in aromatic ring structures (% C A ), naphthene ring structures (% C N ), and paraffin chains (% C p ). 1.2 The values stated in SI units are to be regarded as the standard. 1.2.1 Exception— The values in parentheses are for information only. 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. 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 The carbon distribution and ring content serve to express the gross composition of the heavier fractions of petroleum. These data can be used as an adjunct to the bulk properties in monitoring the manufacture of lubricating oil base stocks by distillation, solvent refining or hydrogenation, or both, and in comparing the composition of stocks from different crude sources. Furthermore, the data can often be correlated with critical product performance properties.