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 and treated until it no longer gives off any steam at all through the pipe, G. The amount of cooling water admitted into the worm, e, that traverses the head, D, is regulated according to the degree of concentration it is desired to give the acid.  As soon as the steam can no longer be separated in the boiler, C, and temperature has reached 118 degrees, the anhydrous acetic acid is distilled through the tube, g, and received in the cooler, K, wherein it condenses.  When the contents of the boiler, A, have been distilled to dryness, the tube, d, is closed and the cock of the tube, c, is opened.  After this, steam is injected directly through the tube, k, in order to distill the acetic acid that still remains in the residuum, and which passes thus through the tube, e, into the worm, h, and flows into the two-necked bottle, S.