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Optical properties of cigarette smoke aerosols.

Although cigarette smoke is frequently utilized as a model laboratory aerosol, its optical properties have still not been established unambiguously. Since the interpretation of many of the classical light scattering techniques are strongly de­ pendent on the optical properties, we have reexamined these for the purpose of fixing their values and clarifying the im­ plications that result. Cigarette smoke is a mixture of organic compounds and water for which reported values of the real part of the refrac­ tive index have been in the 1.43-1.54 range. The higher values, such as determined by Okada, could have occurred as a result of the loss of water and other more volatile materials from the aerosol during the collection process. We have collected cigarette smoke aerosol using an impaction trap, taking extreme care to minimize any such losses from the aerosol. A value of 1.45 was obtained for the real part of the refractive index. While the particular computations to be discussed below (total scattering and absorption cross sec­ tions) are not very sensitive to this discrepancy, the angular intensity functions at large angles do depend strongly upon the real part of the refractive index. On the other hand, this sensitivity to the refractive index can be reduced by confining observations to forward lobe scattering. In order to measure the absorption, whole smoke conden­ sate from thirty Kentucky Reference 2R1 cigarettes (1.1 g) was freshly collected in a mini-impaction trap and dissolved in acetone to a volume of 50 ml. Transmittance spectra of this stock solution were taken, using acetone as a reference, in the Beckman DK-1A spectrophotometer. Satisfactory agreement with the Beer-Lambert law is exemplified in Fig. 1, where the transmittance of the stock solution in a 1-mm cell is compared with that of a tenfold dilution in a 10-mm cell. The efficacy of this procedure for dissolving all absorbing material from the condensate has been corroborated. Figure 2 is a plot of the absorption coefficient K VS wave­ length as calculated from the data of Fig. 1 using the equa­ tion