In summary, nuclear radiation has been widely used to elucidate many aspects of the mechanisms of tobacco being converted to smoke. In addition, the mechanisms of smoke transfer, tobacco inorganic chemistry and smoke filtration have been clarified by many authors worldwide. The newer techniques now being developed, using radiation detection coupled with the enhanced use of electronic-data reduction and interpretation, promise to continue the important role these techniques have played in understanding smoke-formation mechanisms.
The relative positions of the thermal convection column and the smoke plume from a variety of smoldering cigarettes were measured using a combination of schlieren and visual optical systems. The schlieren technique is an optical method used to observe refractive index gradients in gases and other clear media. The refractive index gradients can be caused by variations in pressure, composition or temperature. The convection column of heated air and combustion gases rising from a cigarette coal was observed with a two mirror schlieren system. A video camera was used as the observing device rather than the usual photographic camera. A second video camera was arranged to view the smoke plume rising from the coal region. The two video images were combined with a video special effects generator and were viewed on a single monitor. The behaviour and relative positions of both columns were thus observed in real time with two non-invasive optical methods. The schlieren images of the convection column were compared to those of model systems such as a heated cylinder and a small flame. Results for experimental cigarettes with paper porosities of 12 cm/min to 48 cm/min (Coresta) during smolder showed that the thermal convection column was centered 2 mm to 3 mm in front of the paper char line directly over the hottest part of the coal as determined by infra-red imaging. The smoke plume was centered 2 mm behind the paper char line and the position did not change with paper porosity. Results for experimental cigarettes made with a commercially available low sidestream paper showed that the position of the convection column did not change. However, the position of the smoke plume changed considerably. In addition to being markedly decreased in visibility, the plume now appeared to be centered directly over the paper char line. This change in position provides a valuable insight into the mechanism of smoke reduction. The low sidestream papers seem to work by preventing the escape of smoke forming condensibles through the paper behind the paper char line. The condensibles are therefore forced to escape at the paper char line and undergo increased combustion and pyrolysis. As a result, some are converted to lower molecular weight materials and are unable to condense as readily to form the smoke. In addition, the remaining condensibles are released into a hotter and faster rising gas stream. This serves to reduce smoke formation by suppressing condensation and increasing dilution.
Presented are the results from the use of neutron activation analyses to determine some of the inorganic components of the complete 2R1 reference cigarette, the tobacco filler, the cigarette paper, the dropped ash and the mainstream particulate smoke. Transference values are given for Na, K, Br, Cl, Co, Rb, Al, Sc and Mn. Neutron activation analyses were used to determine butt filtration of selected inorganics in the tobacco rod and in cellulose acetate filters. Butt filtration curves for each 5 mm section behind the cigarette coal were constructed from the data. Na, K, Br and Cl appeared to be removed by normal filtration mechanisms (direct impaction, interception, or diffusion) of entrained particles of inorganic residue coming from the cigarette coal. Vapour condensation of the inorganics studied was not considered a major filtration mechanism because a uniform filtration was observed at distances far enough behind the coal that the smoke would have been at room temperature with essentially all condensation completed. Calcium and magnesium were shown to be removed in such a manner as to indicate a removal mechanism dependent on very large particles enriched in these elements. A proposed mechanism is given to account for the lack of any detectable transference of these elements to mainstream smoke.
The distribution of 14C-menthol (U) and its combustion and pyrolytic products in cigarette smoke is described. The mainstream smoke contains 28.9 percent of the total activity with 44.3 percent in the sidestream smoke and 26.9 percent in the butt. The major 14C-menthol smoke product in the mainstream smoke is unchanged menthol (98.9%). A puff-by-puff plot of menthol delivery is presented. The results obtained are explained hypothetically
JS Brenizer, RW Jenkins, HV Lanzillotti, DD McRae and CA Mora
Neutron radioscopic images of burning cigarettes under both static and dynamic smoking conditions were analysed with a video image processor to measure the changes occurring in the images. These changes were related to the actual mass changes occurring in the cigarette rod during the burning process. The neutron images were used to determine the deposition, movement and evaporation of pyrolysis products in the cigarette rod. In addition, the experimental data were used to calculate the mass burn rates of cigarettes. While the instantaneous mass burn rate of a smouldering cigarette can be measured with a balance, neutron radioscopy can be used to determine it under both static and dynamic smoking conditions. The results of this study, along with background information on neutron radioscopy, calibration methods and the image processing procedures, are presented.
Neutron radiography was used to study the density of tobacco rods. Density variations in individual rods caused by local packing variations and the presence of more dense materials in the blend were easily discernible in both static and real-time radiographs. A density resolution of 0.35 mm was observed in the real-time system. By averaging center line density scans for several rods with the aid of an image processor, large scale variations in the density such as the increased packing at the rod ends could be measured. Comparison of the results from neutron radiography with those obtained by cutting rods into sections and weighing the sections showed good agreement. Both methods indicated the lighting end was approximately 9 % more dense than the middle of the rod. This work has demonstrated that neutron radiography can be used to provide accurate density information about cigarette rods with considerably greater resolution and in much less time than sectioning and the commercial beta ray gauging technique.
The mass balance for chlorine and bromine in the burning 1R1 Kentucky reference cigarette has been determined using neutron activation analyses. Gas radiochromatography has been used to measure dynamically the amounts of gamma-emitting isotopes as they elute from a gas chromatograph. The sidestream and mainstream gas phases which elute from a gas chromatograph appear to be qualitatively identical in their organohalogens, differing only in their quantitative values. The results show that a substantial conversion of ionic halides to organohalogens takes place during smoke formation and this transformation has a threshold temperature below that established during either the puffing or static burn modes of the cigarette. The chemical nature of the halogens present in the mainstream particulate smoke was 10.8 % organochlorine, 88.6 % ionic chloride, 13.3 % organobromine and 86.0 % ionic bromide
R.W. Jenkins, A.F. Frisch, J.G. MacKinnon and T.G. Williamson
Much research has gone into establishing the temperature gradients that exist inside a burning cigarette. These temperature gradients should correspond to changes in the density of the tobacco column due to the condensation and subsequent re-evaporation of volatiles resulting from pyrolysis, combustion, and final ash formation. These dynamic measurements on the burning cigarette were made using a modified beta thickness gauge. A beam of collimated beta particles from a 32P-source is projected through the side of a cigarette at a fixed position. The cigarette is allowed to burn past the focused beta beam. The number of transmitted particles is dependent upon the density of the mass penetrated by the incident particles, and is reflected as a change in the number of counts detected per unit time. A density profile of the burning cigarette has been established for both the puffing and static modes. These density changes are correlated with published temperature profiles. The buildup of the volatile materials (mostly water) on the tobacco rod behind the pyrolytic region is presented. The rate of evaporative losses of these condensables is shown to be dependent on puff count (cigarette length). A detailed density profile of the condensing materials from a single puff has been established. The relationships of these density changes to current smoke formation theories are discussed
R.W. Jr. Jenkins, R.H. Newman, R.D. Carpenter and T.S. Osdene
The distribution of 14C-dotriacontane-16,17 and its combustion and pyrolytic products in cigarette smoke is described. Twenty-one percent of the activity is found in the mainstream smoke, 49 % is found in the sidestream smoke, and 30 % is found in the butt. Of the mainstream activity, 95 % is in unchanged dotriacontane. The transfer of 14C-dotriacontane to mainstream smoke is linear throughout the smoking of the cigarette, as shown by puff-by-puff data. Hypotheses to explain the results are presented
R.W. Jenkins, R.T. Bass, R.H. Newman and M.K. Chavis
The effects of the cigarette periphery on smoke formation have been experimentally studied. A series of cigarettes was prepared with carbon-14 labelled materials placed in different radial positions within the rods. These cigarettes were smoked and the distribution of the radioactivities into total smoke was measured. These data lead to the following conclusions: [1 ] The periphery plays a large contributing role (though not the sole role) in the formation of a) the mainstream particulate phase, b) sidestream particulate phase (derived from non-distillable/non-sublimable materials), and c) mainstream gas phase (derived from non-distillable/non-sublimable materials) ;  The central portion of the cigarette rod plays a large contributing role in a) sidestream gas phase and b) sidestream particulate phase (derived from distillable/sublimable compounds); and [ 3 ] The mainstream gas phase yields from the distillable/sublimable compounds are due in large part to the pyrolysis/combustion products formed during the static burn period. These products are carried into mainstream smoke by the incoming air at the beginning of the puff and by diffusion due to the pressure gradient existing in the cigarette during static burn. These experiments have demonstrated the significant effects that the central portion of the cigarette rod has on sidestream smoke formation and, conversely, the effects of the periphery on mainstream smoke.