TOBACCO. 213 



in the Havana tobacco, is commonly spoken of as ' fullness ' 

 of the smoke, while the relative freedom from the pungent, 

 biting quality is designated by the term ' smoothness.' 



" There are two forms of nicotine contained in tobacco, 

 one of which is easily volatile and readily soluble in petro- 

 leum ether, while the other is volatile only at elevated tem- 

 peratures, and is almost insoluble in petroleum ether. The 

 undesirable sharpness or pungency contained in the smoke 

 from certain types of tobacco, and which constitutes one of 

 the two factors included in the term ' strength ' as applied 

 to the smoke, is due almost entirely to the volatile, easily 

 soluble form of nicotine, which acts as if it were in the free 

 state. On the other hand, the true physiological effects of 

 the smoke, as embodied in the term ' fullness,' are propor- 

 tional to the total quantity of nicotine. 



"The pungent, harsh quality of the smoke is partially, but 

 not entirely, removed by protracted re-sweating and ageing 

 of the tobacco, whereby the easily volatile nicotine is largely 

 expelled." 



Burning Qualities of Tobacco. — It is well known that 

 factors such as character of soil, the climate, wet and dry 

 seasons, the fertilisers applied, and curing, modify tho burn- 

 ing quality of tobacco. 



As applied to tobacco, the term ' burning qualities ' is 

 a comprehensive one, including several different elements, 

 chief of which are fire-holding capacity, the evenness and 

 completeness of the burn, and the character of the ash. The 

 fire-holding capacity refers simply to the length of time the 

 tobacco will continue to burn. Frequently samples of tobacco 

 which possess a satisfactory fire-holding capacity show a 

 tendency to carbonise, or ' coal,' in advance of the burning 

 area, and will not burn evenly. In cigars, this may be due 

 to poor combinations of filler, binder, or wrapper, or in 

 peculiar chemical properties of the leaf. 



As to the quality of the ash, the important characters 

 are colour and the firmness or cohesiveness. If certain of the 

 mineral constituents of the tobacco which interfere with the 

 combustion predominate, the resulting ash will be dark in 

 colour, while if others which favour the complete combustion 

 predominate, the ash will be white, or nearly so. 



"Generally, those substances which show the greatest ten- 

 dency to burn with a flame have the least capacity for glow- 

 ing, and vice versa; and this rule is applicable to different 



