250 Ohservations on Fermentation, 



various substances possess, the processes for making vine- 

 gar are very numerous. But to have this acid in the greatest 

 perfection, it is nccessarv to attend to certain circumstances 

 favourable to its production. These I think may be stated 

 as follows. 



1 . The Presence of Alcohol, or of Matters capable of 

 furnishing it. 



All alcoholic liquors are capable of going through the 

 acetous fermentation. The more alcohol these liquors con- 

 tain, the more acid they afford. We must observe, how- 

 ever, that pure spirit of wine cannot be changed into vine- 

 gar. Besides the vegetable fermenfatable matter, it is ne- 

 cessary that this liquid should be diluted with water, other- 

 wise but a small quantity of vcrv strong vinegar is produced. 

 And as the vinegar in this state of concentration is able to 

 dissolve the alcohol, it lays hold on the existing quantity, 

 and prevents its being acidified. Hence it is that the best 

 vinegars are obtained from the strongest wines. There is 

 generally some alcohol united with the acid, and imparts to 

 good vinegars the agreeable odour which they possess. 



2. The Presence of a vegetahle fermentable Matter. 



It is almost impossible to be ignorant of the agency of 

 this matter in the acetous fermentation. Every one knows 

 that wine deprived of this will not become sour ; therefore 

 the vinegar-makers reject wines which have been fined. It 

 is equally well known, that wine soonest becomes sour 

 when the lees are well shaken; and when the cuttings of 

 the vine, the stalks of the grapes, and the dregs from the 

 press, as well as tartar, gluten, leaven, and other vegetable 

 matters are added to the wine, all of which act upon it as a 

 ferment. 



3. The Contact of Air. 



Chemists are agreed in regarding the air as indispensable 

 to the acetous fermentation, and some correct experiments 

 have been related in support of this proposition. Becher, 

 however, pretends to have made vinegar in close vessels. 

 M. Vauquelin has a'so made some vinegar, by filling a bot- 

 tle with a solution of sugar, containing some gluten, and 

 well stopping the bottle when full. 



4. A Temperature from 18 to 22.* 

 Wine will become sour at a lower tempera ure than this; 

 but then the i'ermentation is weak, and docs not go through 

 its stages v.'ith such regularity as when the atmosphere is of 



• 72 to &2 Fahrenheit. 



the 



