Observations on Fermenlatmi. 225 



the most suitable temperature for the vinous fermentation. 

 Below this degree it languishes; above it, it becomes tumul- 

 tuous. But it is not the temperature of the place only, where 

 the fermentation is going on, which influences it ; the Abb6 

 Rozier has proved that the temperature of the grapes, at the 

 time of the vintage, has a considerable effect upon it, thai 

 the fermentation is always slow in proportion to the low 

 temperature of the grapes when they are gathered. This 

 phtenomenon was observed last year at Montpellier. The 

 vintage did not commence till the latter end of October, 

 and the weather was cool ; the mii^t fermented badly in the 

 vat, and the wine produced from it was not so strong; it 

 appeared more tart than usual when it was tunned. This 

 v/ine did not part with its bad qualities until it had under- 

 gone a new fermentation in the vessel, which continued 

 some months. 



One very singular circumstance, and which has been 

 shown by M. Chaptal, is, the difficulty of'resloring the 

 temperature of mits(, when it is very low, so as to make the 

 fermentation go on in a regular manner. " I diluted," says 

 the author, " some extract of the must of grapes, with wa- 

 ter at four degrees above the freezing point. I added some 

 yeast of beer to accelerate the fermentation. The fermen- 

 tation took place in a short time, when the temperature 

 was elevated to 16 degrees, but it very soon diminished. 

 A like quantity of extract diluted, and heated to the tem- 

 perature of 16 degrees, for two days before the yeast was 

 added to it, underwent a very regular and complete fermen- 

 tation." 



2. On the Iiifluence of Air on the Vinoits Fermentation. 



In order that fermentation may take place, and go 

 through its stages in a steady and regular manner, it is ne- 

 cessary that there be a free communication between the 

 fermenting mass and the air. Should vv-e not cenclude 

 from this fact, that the air enters as a principle into the 

 product of this operation, or as an element of decomposi7 

 tion ? The experiments of M. Chaptal contradict this con- 

 clusion, for he has never seen the air absorbed in the vi- 

 nous fermentation. Its influence is confined to the facili- 

 tating the disengagement of the carbonic acid gas produced, 

 the presence of which would check and even slop the fer- 

 mentation. The free contact of air, aliliougli so u«cful in 

 this respect, has, however, one disadvantage, that it occa- 

 sions a considerable loss of aroma and alcohol. Thus it is 

 well known that wine fermeiutd in vessels nearly close, is 



Vol. 38. No. 161. Sept. 1811. P often 



