m 
a change in the principles of saccharine matter, in 
a process called vinous fermentation. 
The expressed juice of the grape contains sugar, 
mucilage, gluten, and some saline matter, princi- 
pally composed of tartaric acid : when this juice, 
or must , as it is commonly called, is exposed to the 
temperature of about 70°, the fermentation begins; 
it becomes thick and turbid ; its temperature in- 
creases, and carbonic acid gas is disengaged in 
abundance. In a few days the fermentation ceases; 
the solid matter that rendered the juice turbid falls 
to the bottom, and it clears ; the sweet taste of 
the fluid is in great measure destroyed, and it is 
become spirituous. 
Fabroni has shown that the gluten in must is 
essential to fermentation ; and that chemist has 
made saccharine matter ferment, by adding to its 
solution in water, common vegetable gluten and 
tartaric acid. Gay Lussac has demonstrated that 
must will not ferment when freed from air by 
boiling, and placed out of the contact of oxygene ; 
but that fermentation begins as soon as it is 
exposed to the oxygene of air, a little of that 
principle being absorbed ; and that it then 
continues independent of the presence of the 
atmosphere. 
In the manufacture of ale and porter, the sugar 
formed during the germination of barley is 
made to ferment by dissolving it in water with a 
little yeast, which contains gluten in the state pro- 
per for producing fermentation, and exposing it 
to the requisite temperature ; carbonic acid gas is 
given off as in the fermentation of must, and the 
liquor gradually becomes spirituous. 
