20 BURNING QUALITIES OF TOBACCO. 



necessary to impart the property of glowing to tobacco no doubt is 

 influenced to some extent by variations in the other organic constitu- 

 ents of the leaf, but our experiments have shown that excessive 

 quantities of these salts tend to injure the burn by causing a too 

 rapid combustion. It may happen, therefore, that a sample of 

 tobacco contains more organic potash than is necessary to produce 

 the best burn, and in such cases a portion of it could be replaced to 

 advantage by lime. Since magnesia compounds as a whole tend to 

 injure the burn it seems certain that the replacement of potash to any 

 considerable extent by this element would seriously injure the burning 

 properties. 



For purposes of experimentation looking to the production of 

 tobaccos possessing superior burning qualities, either by means of 

 fertilizers and improved methods of curing and fermentation or by 

 breeding and selection, it is very desirable to have at hand some 

 method of testing the results by chemical examination. This is 

 especially true because of the complexity of conditions which influ- 

 ence the qualities of tobacco. For example, if the attempt is made to 

 improve the burning qualities by the use of certain potash salts, with 

 a view to increasing the amount of potash in organic form in the 

 tobacco, the result of the experiment may be entirely obscured by 

 extraneous factors, such as improper curing and fermentation, if the 

 fire-holding capacity alone were determined. Of course, in this 

 particular case chemical analysis would reveal whether the object 

 sought had really been attained, but there are other questions of 

 chemical composition pertaining to this problem which can only be 

 measured with difficulty by the methods at present available. This 

 is especially true of the manner in which the bases are distributed 

 among the acids in tobacco and whether this distribution is essentially 

 different in different samples. 



All of the important organic acids, and also nitric acid, when com- 

 bined with potash seem to be about equally efficient in promoting 

 the fire-holding capacity. Oxalic acid, however, is probably always 

 combined with lime and so it is of little value in this connection. 

 Since a portion at least of the potash combined with organic acids, 

 as well as that present in the form of nitrate, will appear in the ash 

 of the tobacco as carbonate, the determination of this latter quantity 

 gives a rough measure of the amount of these salts originally present 

 and is therefore by far the most important single criterion for judg- 

 ing the burning qualities in a chemical way. 



We have tested a number of samples of tobacco grown in Con- 

 necticut in this way, in each case using one half of the leaf for test- 

 ing the alkalinity of the ash and the second half for finding the fire- 



105 



