significance And Use:

scope:

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.

(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.

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.