ODORIFEROUS PRODUCTS. 315 



mented liquids, and distils over with alcohol when a gentle hea» 

 is applied. 



It is observed that a greater quantity of alcohol is obtained 

 when the mash is made quite neutral by ashes or by carbonate 

 of lime, and that the proportion of oil in the brandy also is in- 

 creased. 



Now, it. is known that brandy made from potatoe starch, which 

 has been converted into sugar by dilute sulphuric acid, is com- 

 pletely free from the potatoe oil, so that this substance must be 

 generated in consequence of a change suffered by the cellular 

 tissue of the potatoes during their fermentation. 



Kxperience has shown that the simultaneous fermentation or 

 putrefaction of the cellular tissue, by which this oil is gene- 

 rated, may be completely prevented in the fabrication of brandy 

 from corn. 



The same malt, which in the preparation of brandy yields a 

 fluid containing the oil of which we are speaking, affords, in the 

 formation of beer, a spirituous liquor in which no trace of that oil 

 can be. detected. The principal difference in the preparation of 

 the two liquids is, that in the fermentation of wort, an aromatic 

 substance (hops) is added, and it is certain that its presence 

 modifies the transformations which take place. Now, it is known 

 that the volatile oil of mustard, and the empyreumatic oils, arrest 

 completely the action of yeast ; and although the oil of hops does 

 not possess this property, still it diminishes, in a great degree, the 

 influence of decomposing azotized bodies upon the conversion of 

 alcohol into acetic acid. There is, therefore, reason to believe 

 that some aromatic substances, when added to fermenting mix- 

 tures, are capable of producing very various modifications in the 

 nature of the products generated. 



Whatever opinion, however, may be held regarding the origin 

 of the volatile odoriferous substances obtained in the fermenta- 

 tion of wine, it is quite certain that the characteristic smell of 



* In the manufactory of M. Dubrunfaut, so considerable a quantity of thi» 

 oil is obtained under certain circumstances from brandy made from potatoes 

 that it iirght be employed for tbe purpose of illuminating his whole manu- 

 factory. 



