10 BUBNING QUALITIES OF TOBACCO. 



tant still, with so many acids and bases present in the leaf, there is the 

 possibility of very considerable differences in the distribution of the 

 latter among the former, and in some cases these differences would 

 certainly exert a very important influence on the burning qualities. 

 It is quite impossible, however, to obtain any information as to the 

 way in which the bases are distributed between the acids in different 

 tobaccos by any available methods for the analysis of the ash. A 

 very large number of analyses have been made of the ash of various 

 sorts of tobacco grown in different parts of the world, but no one has 

 been able to point out any constant relation between the varying 

 quantities of the constituents of the ash and the differences in 

 burning qualities. 



It is to be regretted that in all these analyses no attempt has been 

 made to distinguish between the sulphur existing in the plant as 

 sulphate and that combined with organic compounds, although it 

 has long been recognized that both forms are actually present, and in 

 the case of some plants it has been found that the content of organic 

 sulphur is much greater than that of sulphates. By the methods 

 commonly used in the preparation of the ash for analysis, varying 

 proportions of this organic sulphur are oxidized to sulphuric acid, 

 while the remainder is lost; hence such analyses are valueless as a 

 measure of the quantity of sulphate originally contained in the 

 sample. 



As opposed to the method of directly analyzing samples of tobacco 

 with good and bad burning qualities, what may be called the " syn- 

 thetical method " consists in determining the effect on the burn of 

 adding to tobacco or some other suitable substance those compounds 

 normally occurring in the leaf. It is difficult to get quantitative 

 results in this way, but, on the other hand, positive results in a quali- 

 tative way can be obtained, which in the case of any one constituent 

 added are largely independent of the effects of the other constituents. 

 In this way conclusions are based on direct experiment and do not 

 depend on the differentiation of several factors operating simultane- 

 ously and perhaps in opposite directions. 



Schlosing a was the first investigator to study the problem by this 

 method. He showed that the fire-holding capacity is not propor- 

 tional to the amount of potassium nitrate, and concluded that potash 

 in combination with organic acids is the principal factor favoring 

 this property. If the potash is combined with sulphuric acid and 

 chlorin and the organic acids are in combination with lime, a poor 

 burn results; hence a tobacco with good burning qualities contains 

 potash in excess of that equivalent to the sulphuric and hydrochloric 

 ncids. Schlosing attributed the beneficial action of the potash salts 



" Landw. Vers. Stat, 3, 98. 

 105 



