Red DuraCHAPTER XVIII. Colouring Matters of Unknown Constitution.

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 "Red Dura" or "Durra" of the Soudan, also known as "Shikytan," consists of the deep reddish-brown sheaths of a grass, apparently the Andropogon sorghum (Brot), var. vulgaris, also known as the Sorghum vulgare (Pers.) or "Great millet," the grain of which provides so important a foodstuff. According to E. P. Brown, Inspector of the Blue Nile Province, the "Shikytan" is used for producing a red dye, practically utilised for staining a grass called "lanzura," employed in the manufacture of coloured "bursh" mats, but occasionally for the leather of "markubs" (Sudanese shoes). It is specially grown for dyeing purposes. A full account of the S. vulgare is given by Watt ("Dictionary of Economic Products of India," 6, [iii.], 289). The grain occasionally possesses a brick-red colour, and that at Harihar is used for preparing a red morocco from goat skin. The canes of S. saccharatum also, when pressed and allowed to ferment, develop a red or reddish-brown colour, and the dye thus produced can be extracted by means of dilute alkali. The Indian, Persian, Abyssinian, and Egyptian forms would seem to be derived from the A. sorghum, var. durrha; but the fact that this plant is so extensively cultivated in Egypt as a foodstuff and the "Shikytan" is grown entirely for dyeing purposes, seems to indicate that this latter is again a special variety.

The colouring matter, durasantalin, to which the formula C₁₆H₁₂O₅ has been provisionally assigned (Perkin, Chem. Soc. Trans., 1910, 97, 220), consists of a bright red or scarlet powder, possessing an ill-defined crystalline structure. It is soluble in alkalis with a redviolet colour, passing rapidly to brown on air oxidation, gives with alcoholic ferric chloride a brown liquid, and when fused with alkali, p-hydroxybenzoic acid and phloroglucinol, together with a trace of a third substance, probably p-hydroxyacetophenone, are produced. Durasantalin does not dye mordanted calico, but behaves as a substantive dyestuff towards wool upon which it produces a dull-red shade. A very permanent and slightly fuller colour can be produced by previously mordanting the wool with chromium. In some respects this dye resembles the santalin of sanderswood, but there can be no doubt that these substances are chemically distinct.