8 BURNING QUALITIES OF TOBACCO. 



As applied to tobacco, the term " burning qualities " is a compre- 

 hensive one, including several different elements, chief of which are 

 the fire-holding capacity, the evenness and completeness of the burn, 

 and the character of the ash. The fire-holding capacity refers sim- 

 ply to the length of time the tobacco will continue to burn. Fre- 

 quently samples of tobacco which possess a satisfactory fire-holding 

 capacity show a tendency to carbonize, or " coal," in advance of the 

 burning area and will not burn evenly. In some cases these defects 

 appear to be due to injudicious combinations of the three component 

 parts of the cigar, namely, the filler, the binder, and the wrapper; 

 in other cases the cause lies in the chemical composition of the leaf. 

 As to the quality of the ash, the important characteristics are the 

 color and the firmness or cohesiveness. There is an essential differ- 

 ence between the combustion of most substances and the burning of 

 tobacco. In the first case, the substance when ignited burns with a 

 flame, and as soon as the flame is extinguished the combustion ceases. 

 On the other hand, tobacco of good quality will not burn with a 

 flame, but will continue to glow almost indefinitely. 



It may be said in general that those substances which show the 

 greatest tendency to burn with a flame have the least capacity for 

 glowing, and vice versa, and this rule is applicable to different kinds 

 of tobacco, for in cases of very rank growth where the leaf is thick 

 and coarse or in any tobacco markedly deficient in mineral constitu- 

 ents there is a decided tendency to burn with a flame, whereas the 

 capacity for glowing is lacking. The differences in the two kinds 

 of combustion are well illustrated by the case of coal and its decom- 

 position products when subjected to dry distillation. The volatile 

 products, the larger portion of which goes to make up the illuminat- 

 ing gas, are inflammable, while the residual coke, consisting essen- 

 tially of carbon, yields no flame when burned, but under favorable 

 conditions will continue to glow until consumed. Now, in the burn- 

 ing cigar these two processes are both going on simultaneously and 

 more or less independently of one another. The organic constituents 

 of the leaf in the region immediately in advance of the burning area 

 are undergoing the process of dry distillation, in which the volatile 

 products for the most part escape and appear in the smoke. More- 

 over, it is this process which gives rise to the aroma. As the fire 

 advances, the residue from the distillation, which consists of the 

 mineral constituents of the tobacco, together with more or less car- 

 bon and stable organic condensation products, becomes incandescent, 

 and the glow continues until practically all of the combustible matter 

 is consumed, leaving as the final residue the ash. If certain of the 

 mineral constituents of the tobacco which interfere with the com- 

 bustion predominate, the resulting ash will be dark in color, while if 



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