1.1本实施规程包括通过成分分析近似测定商用丙烷、特殊用途丙烷、商用丙烷/丁烷混合物和商用丁烷（由规范涵盖）的以下物理特性 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为了计算发动机辛烷值，本规程仅适用于含有20 % 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2所示成分的混合物 表1 . 表1确定液化石油气物理特性的因素 A. 组成部分 蒸汽压混合系数，kPa表压 （PSIG）37.8°C（100°F） 15.6°C（60°F）下的相对密度 MON混合值 甲烷 17547 (2545) 0.3 . . . 乙烷 4213 (611) 0.3563 100.7 乙烯（乙烯） 8720 (1265) 0.37 75.6 丙烷 1200 (174) 0.5072 97.1 丙烯（丙烯） 1466 (213) 0.5226 84.9 甲基丙烷（异丁烷） 400 (58) 0.5629 97.6 n -丁烷 255 (37) 0.5842 89.6 t-2-丁烯 242 (35) 0.6099 … 1-丁烯 328 (48) 0.6004 80.8 2-甲基丙烯（异丁烯） 340 (49) 0.6004 … c-2-丁烯 216 (31) 0.6275 83.5 2,2-二甲基丙烷（新戊烷） 152 (22) 0.5961 80.2 环戊烷 -33 (-4.7) 0.7503 84.9 2-甲基丁烷（异戊烷） 40 (5.8) 0.6251 90.3 正戊烷 6.4 (0.9) 0.6307 62.6 正己烷 -67 (-9.7) 0.6641 26 A. 一些 蒸汽压和发动机辛烷值的常数是经验值，仅在本规程所述的计算程序中使用。参考文献位于 附录X1 . 1.2以国际单位制表示的数值应视为标准值。 括号中给出的值仅供参考。 1.2.1 例外情况- 马达辛烷值和相对密度分别以MON数和无量纲单位表示。 ====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 . TABLE 1 Factors for Determining the Physical Characteristics of LP-Gases A Component Vapor Pressure Blend Factor, kPa-gage (PSIG) at 37.8°C (100°F) Relative Density at 15.6°C (60°F) MON Blend Value Methane 17547 (2545) 0.3 . . . Ethane 4213 (611) 0.3563 100.7 Ethene (Ethylene) 8720 (1265) 0.37 75.6 Propane 1200 (174) 0.5072 97.1 Propene (Propylene) 1466 (213) 0.5226 84.9 Methylpropane (Isobutane) 400 (58) 0.5629 97.6 n -Butane 255 (37) 0.5842 89.6 t-2-Butene 242 (35) 0.6099 … 1-Butene 328 (48) 0.6004 80.8 2-Methylpropene (Isobutylene) 340 (49) 0.6004 … c-2-Butene 216 (31) 0.6275 83.5 2,2-Dimethylpropane (Neopentane) 152 (22) 0.5961 80.2 Cyclopentane -33 (-4.7) 0.7503 84.9 2-Methylbutane (Isopentane) 40 (5.8) 0.6251 90.3 n-Pentane 6.4 (0.9) 0.6307 62.6 n-Hexane -67 (-9.7) 0.6641 26.0 A Some  constants for vapor pressure and motor octanes are empirical values to be used only in the calculation procedures described in this practice. References are located in Appendix X1 . 1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only. 1.2.1 Exception— Motor octane number and relative density are given in MON numbers and dimensionless units, respectively. ====== 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.