Combustible mixtures in air

Revised material in Section 5 includes an extensive tabulation of binary and ternary azeotropes comprising approximately 850 entries. Over 975 compounds have values listed for viscosity, dielectric constant, dipole moment, and surface tension. Whenever possible, data for viscosity and dielectric constant are provided at two temperatures to permit interpolation for intermediate temperatures and also to permit limited extrapolation of the data. The dipole moments are often listed for different physical states. Values for surface tension can be calculated over a range of temperatures from two constants that can be fitted into a linear equation. Also extensively revised and expanded are the properties of combustible mixtures in air. A table of triple points has been added. 

These ai e, of course, the limits for the air-free mixture. But remember, the original mixture, before we removed the air, had 2% O2. So the lower limit for the original mixture (with the air added back) is 25.4% + 2/0.209 = 35.0 (the increased lower limit means greater percentage of the combustible mixture in air or lower percentage of air required with the combustible mixture to cause combustion). It is logical that less air is needed since the original mixture (with the air added back) has a head start on combustion (with the contained 2% O2). 

Flash Point is given in degrees Celsius, usually using a closed cup. When the method is known, the acronym appears in parentheses after the value closed cup (CC), Cleveland closed cup (CCC), open cup (OC), Tag closed cup (TCC), and Tag open cup (TOC). Because values will vary with the specific procedure employed, and many times the method was not stated, the values listed for the flash point should be considered only as indicative. See also Table 5.23, Properties of Combustible Mixtures in Air. 

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