270 TOBACCO PRODUCTION IN THE UNITED STATES. 



every one knows that a porous coal remains longer incandescent than a compact one. On the other hand, if we examine the combustion 

 of tobacco, c. #., a cigar, we will observe that the action of heat produces two classes of effects. Volatile substances (smoke) and coal 

 are formed, which latter chiefly sustains the combustion, as it burns out as it forms. If a cigar contains enough of those salts which, 

 when ignited, swell up while decomposing, it will leave a porous coal, throughout which the other substances of the tobacco are finely 

 distributed, and will consequently " hold fire" for a long time. If, on the other hand, the cigar contains little or no organic potash salt, 

 but only sulphate or chloride, neither of which plays any role in the combustion, and if the malic, citric, etc., acids are combined with 

 lime, the constituents of the tobacco do not swell up in burning, but leave a compact coal which does not loug remain incandescent. 

 In the latter case the cigar carbonizes, and the resulting coal still shows the structure of the leaf. 



I will not say that in a difficultly combustible tobacco there are no organic potash salts, that all the potash is in the form of sulphate 

 and chloride, but only that the combustibility of tobacco is independent of its thickness, porosity, ripeness, and composition. A tobacco, 

 therefore, burns well it' it contains enough organic potash salts; it burns badly or not at all if it contains too little, and the pnwence of 

 earbomiti- of potash in the ash is a sign of the good combustibility of tobacco, as its absence is a sign of incombustibility. 



The connection between the presence of carbonate cf potassium in the ash and the combustibility of tobacco 

 was also observed by Ncssler (op. cit., p. 32, et seq.) almost simultaneously with Schloesing. While the results 

 obtained by him tend in general to show, in accordance with those of Schloesing, that the ash of " combustible " 

 tobacco always contains a notable proportion of potassium carbonate, he has found, by quantitative determinations, 

 that the combustibility is not so strictly proportional to the amount of potassium carbonate in the ash as Schloesing 

 has assumed, at least not when comparison is instituted between tobaccos of different origin. Among the conditions 

 that influence combustibility he mentions that tobacco containing larger quantities of albuminoids and fat may 

 leave a difficultly combustible coal that will only then burn when much potash is present; and, on the other hand, 

 that those *x>baecos burn best that contain the most woody fiber. 



Concern! UK the explanations of Schloesing in regard to the nature of the effect exerted by potassium carbonate 

 in the ash, or rather by the substances that leave potassium carbonate on incineration, on the combustibility of 

 the tobacco, Xessler mentions the following objections, based in part on his own observations and experiments: 



First. In the case of slips of paper, as well as those of tobacco, the combustibility is essentially promoted by 

 saturating them with carbonate or sulphate of potassium. A formation of organic potassium salts is in this case 

 only possible when tobacco is impregnated with potassium carbonate, but not when the paper is so treated, and not 

 when tobacco is treated with potassium sulphate. 



Second. A swelling up of the coal behind the incandescent part, such as Schloesing assumes, is a sign of a bad 

 and not of a good tobacco. 



Third. Acetates of the alkalies do not swell up, or at least hardly do so, and nevertheless promote combustibility 

 like the carbonates. 



Jt will be observed that the authorities just cited admit two conditions as conducive to the perfect combustibility 

 of tobacco, namely: 



1. The presence of a notable proportion of potassium carbonate in the ash. (Schloesiug-Nessler.) 



'2. The presence of a large proportion of woody fiber in the tobacco. , (Nessler.) 



Concerning these points it is to be observed that the presence of a larger proportion of woody fiber is equivalent 

 to the presence of a smaller proportion of the other constituents of the leaf, and on reference to the analyses on 

 Table 1 it will be seen that the seed-leaf varieties are especially rich in cellulose (crude fiber), while the chewing 

 varieties, with the sole exception of the Kentucky tobacco, No. 19, are relatively poor therein. 



Concerning the presence of potassium carbonate in the ash, it will be seen from Table Illthatgreat variations 

 exist in the amounts yielded by the different samples, but that the seed-leaf varieties yield more potassium 

 carbonate than the others, with the sole exception of No. 19. But among the seed-leaf varieties themselves the 

 amount of carbonate of potash furnished on incineration does not stand in any simple relation to the com bustibility, 

 as will be seen from the following instances in which the combustibility was determined by the method of Nessler 

 (op. cit. t p. Co): Pieces 1 to J inch wide were cut from the middle of each leaf, running from the edge to the 

 midrib and avoiding the lateral ribs. These were pressed flat by gentle pressure after slight moistening, and 

 exposed to the air for forty-eight hours. The strips were then ignited on the end, and the lapse of time noted 

 between the first ignition and the extinction of the spark or glowing edge; the burnt edge was then removed with 

 the scissors and the slip reignited, the operation being repeated until the whole slip had been burned from tho 

 edge to the midrib; the mean of the observations for the whole slip was then taken. When six slips had been 

 burned, the maximum, minimum, and mean of the series were noted. The results of these tests, while showing 

 great diversities in the combustibility of even different leaves from the same sample, were nevertheless in a measure 

 characteristically distinct for the different brands. 



Especially interesting were the results obtained with the samples of Connecticut Seed-Leaf, viz: No. 30 

 (Hartford), burned to end of strip 120-1GO seconds ; No. 35 (New Milford) maximum 1C.O, minimum 2.7, mean 7.8 

 seconds. As will be seen from Table III, these samples yielded, on incineration, the same percentage of potassium 

 carbonate. The percentage of cellulose is greater in No. 30; the percentage of citric and malic acids is greater in 

 No. 35. This latter fact would suggest that a difference in the character of the organic salts, and especially a 

 difference in I he relative proportions of acids and bases therein, might have something to do with this marked 

 difference in combustibility. As we are still ignorant of the modes <>l combination in which the mineral ingredients 



870 



