and the
upper part of which is protected against the action of the acid vapors
disengaged during distillation by a lining of refractory clay. The stone
cover, B, is provided with an aperture, b, through which the boiler is
filled. The steam pipe, k, is inclosed in a second pipe, f, provided
with radii. This tube serves as a stirrer; and is set in motion by means
of a pulley, g. The tube, c, is connected with a worm, h, and the tube,
d, which is provided with a valve, leads to the second boiler, C. The
head, D, which acts, by reason of its internal arrangement, as a
dephlegmator, is of enameled iron, and is provided with a thermometer,
f, and an aperture, p. Above the spirals of the worm, e, are placed
strips of glass, the free intervals between which are filled in with
pieces of glass, porcelain, or any other material not attackable by
acids. The arrangement is such that the rising vapors can regularly and
without obstruction traverse these materials of wide surface. The
condensed liquid falls back into the lower part of the boiler. The worm,
e, debouches into a cooler, F, fed with water through the cock, n.

At the bottom of the boiler, A, there is fixed a tubulure, r, closed by
a lever, s, and having a fastening device, o. This tubulure permits of
emptying the boiler into the reservoir, L.

A like arrangement is found in the boiler, C. The valves, V, serve to
introduce steam for heating into the double bottoms of the two boilers.
The water of condensation flows out through the tubes, u. The water for
cooling enters the coolers, F, J, and Z, through the cocks, n, and flows
out through the tubes, v.

The acetate, previously crushed, is placed in the boiler, A, and the
quantity of acid necessary to decompose it is added. The mass is
afterward mixed with care by means of the stirrer, and the distillation
may then proceed at once.

The vapors of acetic acid that are disengaged enter the boiler, C,
through the tube, d, and are kept hot by the steam. In the head, D, they
are separated into two portions, viz., into concentrated acetic acid,
which condenses by reason of its high boiling point, and into steam,
which distills and carries along but a very small amount of acetic acid.
This steam passes through the pipe, G, into the worm, H, condenses, and
afterward flows into the vessel, N.

[Illustration: APPARATUS FOR THE MANUFACTURE OF VINEGAR.]

The acetic acid that accumulates in the boiler, C, must be again
vaporized