A Process for the Treatment of Tannin-containing Extracts from Vegetable Matter, more particularly Extracts of Mangrove Bark.

摘要

24,899. Damk÷hler, H., and Schwindt, H. Oct. 29. Processes and materials for treati n g hides and skins. - Vegetable tanning - extracts, and particularly mangrove-bark extract, are decolorized by generating in them nascent hydroxides of metals by chemical or electrolytic means. The Figure shows a decomposition cell having a cathode comprising a zinc vessel a metallically connected to a perforated aluminium cylinder c, and an anode comprising metallically connected zinc and aluminium plates f, g, within a porous pot e. The pot contains a solution of aluminium and zinc sulphates; and the tanning- liquor under treatment is placed in the outer vessel, together with a proportion of aluminium and zinc sulphates depending on the intensity of the colouring. Other metals may be used for the electrodes, provided that their salts be used to form the electrolyte. The extracts may also be decolorized by purely chemical treatment with the aluminates of the alkaline earths. Barium aluminate is especially suitable, and gives a copious aluminium lake, which may be precipitated by the addition of sulphuric acid or a sulphate. The chemical and electrolytic treatments may be carried out simultaneously, as by adding barium aluminate and sulphuric acid to the tanning-liquor in the cell.