Practical Magazine 14, 1876 48
(Chemistry applied to the Arts, Manufactures, &c.
Dyeing, Calico Printing, Bleaching, Tanning, and Allied Subjects.)
If an electric current is passed through a solution of tannin in a reservoir, the bottom of which is one pole, while the other is at the surface of the liquid, and skins are interposed during the passage of the current, a molecular transmission of tannin from one pole to the other is produced. This tannin thus passes through the skins, which are penetrated with it much more quickly than by the ordinary process. The stoutest leather is thus tanned in thirty or thirty-five days instead of twelve or fifteen months. The skins nearest the positive pole are always penetrated first.
The bottom of the vessel is formed of a plate, or collection of plates, in retort charcoal. A copper wire, surrounded with gutta percha, is fastened to this bottom, and rises along the vertical side. The upper surface is covered with a sheet of zinc, to which the negative pole is fitted. The two poles are in connection with a pile or a magneto-electric machine. The skins are arranged in the reservoir alternately with layers of bark in the usual way.
- Bulletin de la Société Chimique, Nov. 20th, 1875.
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