298 The Soverane Herbe 



The ash consists of potash and ammonia salts and 

 nitrates. The smouldering action of tobacco is caused 

 by the nitrate of potash. Tobacco should burn clearly 

 and freely, but not too rapidly. If it is slow of com- 

 bustion (due to imperfect curing or poor quality), 

 objectionable products such as carbon dioxide are 

 evolved. This is the case with a badly burning cigar. 



But tobacco is never entirely burned. Carbonic 

 acid and water are produced and many other organic 

 substances, which, released or formed by the heat 

 of combustion, are distilled into gases. The con- 

 densation of these volatile substances forms the 

 smoke. The colour as well as the flavour of the 

 smoke, therefore, depends upon the quantity and 

 nature of the substances forming it. 



Among the bye -products of combustion are 

 ammonia and its compounds, an empyreumatic oil 

 found in the stale tobacco or ' dottles ' of bowls, and 

 a dark, bitter, resinous substance or oil in the pipe- 

 stems. ' These organisms,' remarks an authority, 

 ' begin to be deposited directly they are formed (by 

 the burning), so that some remain in the mouth, and 

 if the smoke is swallowed or passed through the 

 nostrils, so much more will be retained and absorbed 

 into the system.* 



The dark bitter oil which forms in the bowls and 

 stems of pipes is popularly regarded as nicotine. This 

 is totally erroneous. It is a joint product of the 

 moisture from the tobacco, produced by combustion 

 and impregnated by smoke. It is really the water 

 of tobacco in combination with the soot and tar of 

 the smoke. Nicotine is colourless, and forms an 



