The Portland daily press. [volume] (Portland, Me.) 1862-1921, 1875-11-03
THE FARM AND HOUSEHOLD.
The Chemistry of the Crane.

The Chemstry OF the Grape.
BY very much the larger part of the juice OF
the fully-ripened grape is natures own arch
solvent, pure water; but this water contains
mingled with IL certain proportion of other
principles that have been elaborated in the
grape during the life of the plant, and are
held dissolved in the water to communicate
to it its sweetness and other delicious quail
ties. OF these principles the chief part is SUI
gar, mingled with a relatively small percent
age of tartaric acid, and with yet more mi
mute trace of various other more or less Or
ganized and complex substances that are
mixed cunningly together by the vegetable
alchemy. to give the various charming attri-
butes of color, favor, and fragrance to the
fruit. In the most essential products of this
vital elaboration the acid is preponderant
during the the early stage OF the formation CT
the berry; but with the advance of matura-
ton the sugar accumulateS more and more,
and the acid falls back into obscurIty for the
most part on account OF being overborne
and masked by the increase of the saccharine
ingredient, but in s"me instances also, it ap-
pears, from the actual conversion of the tar
taric acid into sugar. The sugar produced in
the rpening of the grape is mainly OF pecu-
liar kind spoken of as glucose or grape,
sugar." which is characterized by its pro0e-
ness to undergo the chemical change that
constitutes fermentation. It is chen ically
distiug lished from the sugar OF thescane by
being trifle more rich in hydrogen aud oxy-
gen, and, therefore, somewhat less highly
carbonized. Grape sugar IS capable OF pre-
senting itself in two distinct forms, mainly
distinguished by the odd peculiarly that one
has the power of diverting the plane OF ray
of poarized light passing through it toward
the right, ard the other of diverting the
same ray toward the left. When the grape
sugar has been matured by the oxygenation
and Encouragement of the atoms of the sac
cbarine moecule, and the rich juice, or eX-
pressed must, has been poured into watts.
and left for time in a moderately warm
temperature to its own uncontrolled impuls-
es, further change begins among the lightly
balanced atoms of the sugar molecules. A
further removal OF carbon takes place, and a
new torEl of molecule IS formed out of the ell
ements that remain. The ntw moleCale is
alcohol, or spirit of wine, instead of sugar.
The sweetness is gone from it, and an ardent
favor has taken It's place. The exact chemi
cal character of the new and most remarka-
BILE agent which has been generated by this
piece of molecular legerdemain may perhaps
be better understood if the resulting spirit is
described as liquid in some sense of the ma
ture of water, but in which portion of the
hydrogen of the water molecule has been
withdrawn, and its place supplied by more
complex hydro-carbon molecule. The water
chemical condensation into itself of hydro
carbon, very energetic form of combustible
substance. In order that grape,juice may be
successfully converted into wine OF good quail
ity by the natural process of fermentation, it
is found that it must not have, in its rIpened
state, more than five parts in each 1000, of
tartaric acid and that it must have 200 parts
in each 1000, or twenty per cent, of sugar.
In dry, warm years this proportion is readily
and commonly secured; but in less genial
seasons the ripening is less perfect, and the
grape.juice contains more acid and less sugar.
The wine that is then made from the must Is
of very inferior and unsatisfactory quality.
The first attempt to rectify this evil consisted
in the removal by chemical means of the SUI
perfuous portion of the acid, and of the addi-
ton OF what was conceived to be the deficient
amount of grape-sugar derived from other
sources. This expedient, however, did not
answer, and better process was afterward
secured by diluting the must until the acid
was lowered to the requisite amount, and
then adding cane-sugar until due sweetness
was secured. By this process very excellent
wines are now made in the less favorable sea-
sons. When the must of the grape contains
the appropriate twenty per cent. Of sugar the
result of the fermentation is wine which
has at the most some eleven per cent. of alb
solute alcohol, or nineteen per cent by vol
ume, of proof spirit. This is as high pro-
portion of alcohol as can be produced by the
natural fermentation of the grape juice, ane
therefore it becomes the standard of the high
est strength of natural wines. All alcohol
contained in wines beyond this proportion
must have been produced by distillation as
spirit. and have then been added - the wine
ia that state. The reason for this is that in
presence of fourteen or fifteen per cent. of al
cohol all further conversion of sugar into al
cohol by fermentation is arrested. 1t rich
juice containing more than twenty per cent.
OF sugar is fermented there always remains
considerable amount of unconverted sweet
ness IN the wine after the fermentation has
been carried on as far as it can, and this re-
mainder is protected from further change
by the presence of the spirit. The natural
wines which have a strength of eleven or
twelve per cent. OF absolute alcohol, rarely
retain more than half of one per cent. of mn
converted overwhelmingly Reuiew.