Fig. 59.—Babool (Acacia arabica).
MIMOSEÆ, a Tribe of Leguminosæ.
Acacia arabica, “Babool,” “Babul,” India, Egypt. [Fig. 59]. Bark contains about 12-20 per cent. of catechol tannin; one of the principal Indian tanning materials, used for kips and heavier leathers. Pods, used in India for bating, contain about same amount of tannin as bark, but of a different kind, that of the bark being a catechol-tannin, with a good deal of red colouring matter, while the pods contain a paler tannin allied to divi, which is not precipitated by lime-water. In Egypt the pods are called bablah, a name which is also applied to pods of A. cineraria and A. vera, and others. They are used for dyeing glove-leathers.
A. nilotica, Egypt. Pods called neb-neb or bablah.
Fig. 60.—Cutch Tree (Acacia catechu).
A. catechu, India. The wood yields cutch or “dark catechu.” A lighter coloured variety called kath, containing much crystallised catechin, is also made in India, and principally used for chewing with betel. A. catechu is a tree 30-40 feet high, common in India and Burma, and also in tropical East Africa, where, however, it is not utilised. In Southern India, A. suma is also used for the same purpose.
Trees of about 1 foot diameter are cut down, and the wood (some state the heart-wood only) is reduced to chips, and boiled with water in earthen jars over a mud-fireplace. As the liquor becomes thick and strong, it is decanted into another vessel, and the evaporation continued till the extract will set on cooling, when it is poured into moulds made of leaves or clay, the drying being completed by exposure to the sun and air. “Kath,” or pale cutch, is made in Northern India, by stopping the evaporation at an earlier point, and allowing the liquor to cool, and crystallise over twigs and leaves thrown into pots for the purpose. It contains a large proportion of catechin, apparently identical with that of gambier, but its tannin is much redder. Good cutch contains about 60 per cent. tanning matter, but is principally used for dyeing browns and blacks with chrome and iron mordants. It contains quercetin, a yellow colouring matter ([p. 263]).
A. leucophlea, India and Java “Pilang.” Pods and bark equal to A. arabica.
Australia abounds in acacias (mimosas), many of which are used in tanning, but vary greatly in strength, not only according to species, but probably also by situation and growth. Probably the best information is to be found in a pamphlet on ‘Wattles and Wattle-Bark,’ by J. H. Maiden, F.L.S., published by the Department of Public Instruction at Sydney, 1890. His analyses were made by the Löwenthal process, and can only be roughly compared with those by the hide-powder method. The analyses given are by the I.A.L.T.C. method, and mostly on samples furnished by Mr. Maiden.