ODORIFEROUS PRODUCTS. 345 



the Herha centaurium minorius, a plant which pos- 

 sesses no smell. When it is exposed in water to a 

 slightly elevated temperature it ferments, and emits 

 an agreeable penetrating odor. By the distillation 

 of the liquid, an ethereal oily substance of great vola- 

 tility is obtained, which excites a pricking sensation 

 in the eyes, and a flow of tears. (Biichner.) 



The leaves of the tobacco plant present the same 

 phenomena; when fresh they possess very little or 

 no smell. When they are subjected to distillation 

 with water, a weak ammoniacal liquid is obtained, 

 upon which a fatty crystallizable substance swims, 

 w^hich does not contain nitrogen, and is quite desti- 

 tute of smell. But w^hen the same plant, after being 

 dried, is moistened with water, tied together in small 

 bundles, and placed in heaps, a peculiar process of 

 decomposition takes place. Fermentation com- 

 mences, and is accompanied by the absorption of 

 oxygen ; the leaves now become w^arm and emit the 

 characteristic smell of prepared tobacco and snufF. 

 When the fermentation is carefully promoted and 

 too high a heat avoided, this smell increases and be- 

 comes more delicate; and after the fermentation is 

 completed, an oily azotized volatile matter called 

 nicotine is found in the leaves. This substance, 

 — nicotine, which possesses all. the properties of a 

 base, was not present before the fermentation. The 

 different kinds of tobacco are distinguished from one 

 another, like wines, by having very different odori- 

 ferous substances, which are generated along with 

 the nicotine. 



We know, that most of the blossoms and vegetable 

 substances which possess a smell owe this property 

 to a volatile oil existing in them; but it is not less 

 certain, that others emit a smell only when they 

 undergo change or decomposition. 



Arsenic and arsenious acid are both quite inodor- 

 ous. It is only during their oxidation that they emit 

 their characteristic odor of garlic. The oil of the 

 berries of the elder-tree, many kinds of oil of turpen- 



