Apparatus for use in the determination of volatile acids in wines and vinegars

Issued August 18, I'JOO.

United States Department of Agriculture,

BUREAU OF CHEMISTRY— Circular No. 44.
H. W. WILEY, Chief of Bureau.

APPARATUS FOR USE IN THE DETERMINATION OF YOLATILE ACIDS
IN WINES AND VINEGARS.

By H. C. GOKE,
Assistant Chemist, Division of Foods,

lu tliis modification of tlie Hortvet-Sellier apparatus « a copper flask is sub-
stituted for tlie outer glass flaslv and a constant feed device for the flask has
been added ; there are also two changes of a minor nature consisting in a small
ridge blown in the inner flask to form a shoulder for the rubber gasket and the
elimination, as unnecessary, of the dropping funnel. The constant water feed
is operated by running the supply water through tube a (fig. 1), which passes
through tube &. The overflow passes through h and rises through tube c to the
small basin d, which is connected with the drain. Tube a is placed within tube
?', because steam is so prevented from passing out through 1). Distilled water
should be used which has been largely freed from carbon dioxid by washing it
from twenty to thirty minutes with a rapid stream of air. The water should
be admitted somewhat more rapidly than it is used. The rate of flow is con-
veniently regulated by comparing the rate of drip in the small sight tube e with
that from the condenser. Experiments with the. apparatus showed that when
tap water was supplied to the generator there was an error due to the presence
of carbon dioxid in the distillate, equal to about 0.3 cc of tenth-normal alkali in
100 cc, phenolphthalein being used as indicator. When ordinary distilled water
was used, the error was about 0.15 cc. When distilled water was employed from
which the greater portion of carbon dioxid had been removed by aerating, the
error was but 0.05 cc. The error is constant and may be subtracted from each
determination.

The apparatus is operated as follows:

Place 10 cc of the sample in the inner flask, which should have been removed
from the outer flask and be entirely cool. If the sample is noticeably charged
with carbon dioxid, pass through it a current of air for a few minutes by attach-
ing to the flask a stopper bearing a glass tube wjiich is connected with suction.

« J. Ind. Eng. Chem., 1909, 1 : 31.

XMr. 44]
2711—09 *

The air passes in through the side tube in the flaslv and washes out practically
all of the carbon dioxid in the sample without removing appreciable quantities
of volatile acid. Connect the flask with the distilling bulb and place in the
outer flask, tube / of the outer flask being open. Make all connections tight and
close tube /, In the case of wines, collect about 100 cc of the distillate. In the
case of vinegars, from 200 to 300 cc are required. Titrate distillate with stand-

ard alkali free from carHlwiates using phenolphthalein as indicator and subtract
0.05 cc for each 300 cc (i^^ distil late. About fifteen minutes are required for a
determination of volatile |icid in win^ and from thirty to forty-five minutes in
the case of vinegar. The volume of* liquid in the inner flask increases but very
slowly during a determination. The apparatus should find a wide use in the
determination of volatile constituents.
ICir. 44]

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