Observations on Fermentation. 24Q 



aroma and a portion of alcohol, which the disengaged c^.r- 

 bonic acid gas holds in solution. The ingenious idea of 

 making vinegar with the gas taken from the top of ferment- 

 ing vessels, proves this solution of alcohol ; it is confirmed 

 besides by M. Humboldt. Moreover, the impression which 

 the substance in question makes upon our organs, leaves no 

 room to doubt lliat it contains more than carbonic acid gas; 

 it therefore never happens ihat we can exactly imitate it by 

 a simple condensation of this gaseous body. 



-2. Of the Formation of Alcohol. 



In proportion as the sugar of the must, when acted on 

 by the ferment, loses its carbon and oxygen, to form car- 

 bonic acid gas, it loses also some of its hydrogen, which 

 combining anew with oxygen, separated from the sugar, 

 forms water. These continual subtractions change the 

 sugar into a particular product called alcohol ; a word, 

 M. Chaptal thinks, employed in a sense far too general. 

 The quantity of alcohol produced is always in proportion 

 to the quantity of sugar decomposed. A set of phasnomena 

 take place during its decomposition, which I shall not now 

 notice. The result is an intoxicating liquor called wine, in 

 which are found alcohol, water, mucilage, tartar, a colour- 

 ing matter, 8cc. M. Chaptal says, the source of the co- 

 louring matter is in the pellicle of the grape, and thai there 

 is an analogy between it and resin : he observes, that it is 

 only dissolved in the must during fermentation, in propor- 

 tion as the alcohol is developed. It is an incontestable fact, 

 that the colour of wine is always in proportion to the quan- 

 tity of alcohol produced. But I do not know that we are 

 to attribute the colouring of the wine solely to the solvent 

 power of the alcohol. Our author notices a colour almost 

 as black as ink, in the very weak wines of the banks of the 

 Cher and the Loire ; and it is not uncommon at Montpellier 

 to eat very ripe grapes, whose juice is of a very red colour. 

 In the year 1809 tlie i7iust here was remarkably high-co- 

 loured at the lime the grapes were pressed, and yet the wine 

 made from it was of a paler colour, and not 50 strong as 

 usual. Are not these positive facts conclusive against the 

 colour of wine solely depending upon the alqohol acting 

 on the pellicle of the grape ? 



3. Of the Acetous Fermentation. 



This fermentation differs from the preceding, in that the 

 product is constantly acetic acid. Owing to the great fa- 

 cility of furnishing this acid by a slight alteration, which 



various 



