WHAT IS WINE? 
37 
Let us now turn to the consideration of the chief con- 
stituents of the wine, more particularly of such as admit of 
quantitative estimation. The most important of these is 
Alcohol . — Ethylic alcohol, or spirit of wine. As before 
explained, the sugar of the must breaks up, in the course of 
fermentation, chiefly into carbonic acid and alcohol, the former 
escaping into the air, the latter remaining in the wine. 
C 6 H 12 0 6 = 2(C 2 H 6 0) + 2CO a 
sugar alcohol carbonic acid 
By submitting the wine to distillation, this alcohol can be 
separated from the rest of the constituents and estimated. 
Generally speaking, all wines which are simply the fermented 
juice of the grape (natural wines) contain from 60 to 130 parts 
by weight of alcohol in 1,000 volumes of wine (6 to 13%). 
With less than 60 parts the wine is scarcely drinkable, and 
more than 130 parts cannot, except in a very few rare cases, be 
contained in a natural wine. Firstly, because grape juice 
seldom contains the requisite amount of sugar for the produc- 
tion of more alcohol than this ; and, secondly, because such an 
amount represses, or altogether stops, fermentation, and so 
protects the rest of the sugar from decomposition. A wine of 
more than 1 3% of alcohol is almost certainly a fortified wine ; 
the great majority of natural wines contain less than 12%. 
In fortified or brandied wines the strength, of course, depends 
on the amount of spirit added, and on the original strength of 
the wane; it may, how r ever, be taken as ranging between 120 
and 220 parts per 1,000 volumes (12 to 22%), being rarely 
above and rarely below that amount. 
Besides this ethylic alcohol wine contains, as we have seen, 
small proportions of a number of other alcohols ; as, for example, 
propylic, butylic, amylic alcohol, &c. &c. These alcohols are 
closely allied, chemically, to ethylic alcohol ; indeed, they are 
termed alcohol on that account, and are, like it, produced 
during the fermentation of sugar. They have, undoubtedly, a 
great influence upon the bouquet of the wine, and perhaps also 
upon its physiological action. At present they do not admit of 
accurate quantitative estimation. 
Acids of Wine . — All wine contains a greater or less propor- 
tion of free acid, and possesses, therefore, an acid reaction and 
a sour taste ; but whilst the degree of acidity, as measured 
chemically, depends only upon the proportion of acid present, 
the acidity, as judged by the palate- — the more or less sour taste 
of the wine — is greatly influenced by the nature of the acid and 
the presence or absence of other constituents. Thus a vine of 
low alcoholic strength, and without sugar, will taste unpleasantly 
sour, with a degree of acidity w T hich, in a strong and sweet 
