1.1 通过成分分析，本规程涵盖了商用丙烷、特殊用途丙烷、商用丙烷/丁烷混合物和商用丁烷（规范涵盖）的以下物理特性的近似测定 D1835 ):蒸汽压、相对密度和发动机辛烷值（MON）。 1.1.1 本规程不适用于任何超过非挥发性残留物规范的产品。（见试验方法 D2158 .) 1.1.2 对于计算发动机辛烷值，本规程仅适用于含有20的混合物 % 或更少的丙烯。 1.1.3 对于计算的发动机辛烷值，本规程基于仅包含表1所示成分的混合物 表1 . 1.2 以国际单位制表示的数值应视为标准值。 1.2.1 例外情况: 1.2.1.1 括号中的非国际单位仅供参考。 1.2.1.2 马达辛烷值和相对密度分别以MON数和无量纲单位表示。 1.3 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《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 4.1 蒸汽压是商用丙烷、特殊用途丙烷、丙烷/丁烷混合物和商用丁烷的重要规格特性，可确保充分汽化、安全并与商用设备兼容。相对密度虽然不是规范标准，但对于确定填充密度和保管转移是必要的。发动机辛烷值（MON）有助于确定产品作为内燃机燃料的适用性。

1.1 This practice covers, by compositional analysis, the approximate determination of the following physical characteristics of commercial propane, special-duty propane, commercial propane/butane mixtures, and commercial butane (covered by Specification D1835 ): vapor pressure, relative density, and motor octane number (MON). 1.1.1 This practice is not applicable to any product exceeding specifications for nonvolatile residues. (See Test Method D2158 .) 1.1.2 For calculating motor octane number, this practice is applicable only to mixtures containing 20 % or less of propene. 1.1.3 For calculated motor octane number, this practice is based on mixtures containing only components shown in Table 1 . 1.2 The values stated in SI units are to be regarded as standard. 1.2.1 Exceptions: 1.2.1.1 Non-SI units in parentheses are given for information only. 1.2.1.2 Motor octane number and relative density are given in MON numbers and dimensionless units, respectively. 1.3 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 ====== 4.1 Vapor pressure is an important specification property of commercial propane, special duty propane, propane/butane mixtures, and commercial butane that assures adequate vaporization, safety, and compatibility with commercial appliances. Relative density, while not a specification criterion, is necessary for determination of filling densities and custody transfer. The motor octane number (MON) is useful in determining the products' suitability as a fuel for internal combustion engines.