Manufacture of Wines in the South, Part II [pp. 251-279]

MANUFACTURE OF WINES IN TIIE SOUTH.
iinportance, for it wvill iniform him whether the error was coimmitted in thle vinta(re or in the fermentation, and the like error
my be avoided on anothler occasion. Knowing thalt I would
lhave manyii wines and juices to examine in order to accomplish
the enid I had in view, I commened(l operations by devisillg the
simplest plans for accoml)lislling the fewest objects. I decided
tlhat tlhe determination of but two actids would answer my purpose. I concluded to unite all the acids of' the girape into one,
unlder the eommoi-i namne of the tartaric; and wlletlicir they be
tartaric, raceinie, nialic or citric, the practical result would be
the si mae, my reagent would act upllon one or all, and if always
applied in the same manner, the same results indicating quantity- would lways flow from juices containing the same quantities. A little practice settled tis point. Comlparative, not
absoltute quantity, was what 1 desired, and that I obtained.
Unldei the impression that the tartaric acid was the most
abundant in tlhe grape, my thoughts turned upon a reagent
best suited to its detection, and the neutral tartrate of potash
was s;elected for triail.
3[- reasons for this choice were that neutral tartrate of potash was soluble in water, and had a strong disposition to unite
with more tartaric acid, and form another compound, bi-tart-rate of p)otash, which was insoluble in water; hence, on the
ad(lition of a solution of neutral tartrate of potash to g(rape
juice, I had the satisfaction of seeing a white precipitate, indicating' the presence of tartaric acid, which white precipitate
was bi-tartrate of potash. It should hlere be remarked, th,t
any- other free acid besides the tartaric will produce the same
prccil-)itate; b)ut we know that there are no other fiee acids in
grape juice than those enumnerated above; and, althlough they
do not uinite to produce the same insoluble salt, their action is
precisely analo(ous. If we form our rea(gent upon citric acid,
bi-tairtrate of potash is formed: not by converting citric acid
into tartaric, but by the union of the citric acid withl a portion
of tlle potash, and thus liberating a portion of the tartaric,
wlhichl immediately uniites withl another portion of the remainin,g neutral tartrate, and converts it into bi-tartrate. Thus it
is ipparent that our reagent exhibits the presence of all the
fiee acids that may be in the juice, and that is precisely what
we desire that it slhould do. The quantity of bi-tartrate precipitated indicates the quantity of all the fiee acids present in
thle juice, without reference to what they may be; and if this
precipitate is carefully separated, diried, and weighled, we can
certainly learn how much lacidity was in the juice, and thus
compare any nunber of juices, or the same juice any number
of times. The same reagent is equally applicable to wihe,
with a certain modification, which enables us to discriminate
between the acid formed during fermentation, and those preexisting in the grape juice. Tlhe only acid which it is import
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