The Natural Organic Colouring Matters
By
Arthur George Perkin, F.R.S., F.R.S.E., F.I.C., professor of colour chemistry and dyeing in the University of Leeds
and
Arthur Ernest Everest, D.Sc., Ph.D., F.I.C., of the Wilton Research Laboratories; Late head of the Department of Coal-tar Colour Chemistry; Technical College, Huddersfield
Longmans, Green and Co.
39 Paternoster Row, London
Fourth Avenue & 30th Street, New York
Bombay, Calcutta, and Madras
1918
Kaikki kuvat (kemialliset kaavat) puuttuvat // None of the illustrations (of chemical formulas) included.
The Lonchocarpus cyanescens (Benth.), a leguminous plant of the sub-order Paplionaceae, is a woody-climber from 10 to 14 feet long. The young leaves contain an indigo-yielding principle, and on this account the plant is employed by the tribes of Sierra Leone and the interior and those of Western Soudan as the source of a blue dye. In the former country the young leaves are collected along with some more matured ones, roughly pounded, and dried in the sun. In this state it is sent into the market as "Gara," and sold to the dyers. The natives of Western Soudan employ the young and tender buds, which are collected, pounded when quite raw, made into balls, and dried in the sun. For dyeing purposes the "Gara" is covered with water, treated with potash and the bark of the Morinda citrifolia (Linn.) and allowed to ferment for some days. The cloth to be dyed is thrown into the vat, left there for some time, and dried in the sun. An examination of "Gara" by Perkin indicated the presence of approximately 0,62 per cent, of indigotin (J. Soc. Chem. Ind., 1907, 389). Apparently also this plant is utilised in Northern Nigeria as a dyestuff in the form of a similar preparation to that described above, and for the manufacture of a crude indigo. A sample of this Nigerian leaf product contained approximately 0,65 per cent, of indigotin, whereas in the indigo the presence of 21,47 Per cent, of indigotin and 1,33 per cent, of indirubin was detected (Perkin, J. Soc. Chem. Ind., 1909, 353). The botanical examination of the former, and also of plant debris contained in the latter, by V. H. Blackman, indicated that they were derived from the L. cyanescens, or some closely related form. Rawson and Knecht (J. Soc. Dyers, 1888, 66) have described similar leaf and crude indigo products, which had been sent to this country by Sir T. Goldie, Governor of the Royal Niger Co., and these respectively contained 0,52 per cent, of indigotin and 39,12 per cent, of indigotin, together with 4,75 per cent, of indirubin. A more recent examination of the leaf fragments in Rawson and Knecht's samples has shown that these possess the same structure as those of the L. cyanescens (Perkin, loc. cit.), and it thus appears evident that in Western Africa this plant is extensively employed for dyeing and the preparation of indigo. There is reason to presume that the indigo yielding principle present in the young leaves of the L. cyanescens gradually disappears when these reach maturity, as samples of the latter examined in this country were devoid of indigo-producing property. The L. cyanescens is probably identical with the "Taroom akkar" described by Bancroft ("Philosophy of Permanent Colours," 1813, i., 189 and 191).
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