220 YERKIN : A NATURAL SUBSTANTIVE DYESTUFF.

XXIV. -A Natural Substantive Dyestuff. By ARTHUR GEORGE PERKIN.

SOME time ago a small sample of an Egyptian natural dyestuff was received from the authorities of the Imperial Institute, under the name of the “ red dura” of the Soudan, the dyeing properties of which proved to be specially interesting in that good shades upon wool could be obtained from it without the aid of a mordant. The material consisted of the leaf sheaths of a, grass, smooth externally, possessing a deep reddish-brown tint, and approximately nine inches in length, together with cylindrical fragments of the stem (or pith) of a brighter, although feebler, colour. The follow- ing account of this plant was furnished by Mr. C. P. Browne, Inspector of the Blue Nile Province: ‘ I I attach a specimen of ‘ Sikhytan,’ the species of durra used for producing a, red dye, practically utilised for staining a grass called ‘ lanzura,’ used in the

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PERKIN : A NATURAL SUBSTANTlVE DYESTUFF. 221

manufacture of coloured ‘ bursh ’ (mats), but occasionally for the leather of ‘ markubs ’ (Sudanese shoes). This durra is specially grown for the purpose and not for eating. It occurs in this district, but comes mainly from Rahad, Dinder, and the south.” The results of the examination of this product a t the Royal Botanic Gardens, Eew, indicated that it was apparently part of the stem, including the leaf sheaths, of the A ndropogon sorghum, var. wdgaris, and this was int.eresting because this plant, also known as the Sorghum wulgare, constitutes the “ Great Millet,” the grain of which is so important a foodstuff. An elaborate account of the Sorghum vulgare is given by Watt (“Dictionary of the Economic Products of India,” Vol. 6, Par t 111, p. 289), and it is worthy of note that in certain cases the grain is described as possessing a brick-red colour, and that a t Harihar this is used for preparing a red morocco from goat skin. Again, it is stated in connexion with the Sorghum saccharaturn that when the pressed canes are allowed to ferment, their colour changes to a red or reddish-brown, and that the dye thus produced can bs extracted by means of dilute alkali, and is precipitated from this solution by means of acid in the form of red flakes. The Indian, Persian, Abyssinian, and Egyptian forms would seem to be derived from the Andropogon sorghum, var. ‘ I durrha” (ibid., p. 278)) but the fact that this plant is so extensively cultivated in Egypt as a foodstuff, whereas, according to Browne (Zoc. c i t . ) , the ‘‘ Sikhytan ” is grown entirely on account of its dyeing properties, leaves one t o infer that this latter is again a special variety. Unfortunately, but a few ounces of this material were available for examination, and this did not permit of any extended investigation of the colouring matter which is present, but should it be possible to obtain a large quantity of this dyestuff, a more exhaustive study of the subject will then be carried out.

Ex P ER IMENTAL.

The leaf sheaths and stems (pith) were examined separately, but as experiment showed that the same products were present in both cases, this was evidently not necessary. The material was extracted in a Soxhlet apparatus with boiling acetone until nothing further dissolved, and by evaporating the deep brownish-coloured extract there was obtained from the sheaths 16-27 per cent., and from the pith 14.7 per cent., of a dark brittle resin. On agitating this residue with cold acetone, a small quantity of substance did not. pass into solution, and the operation was repeated until the final product was entirely soluble under this treatment. The amorphous substance thus removed, and which, when dry, possessed a Slight beetle-green lustre, on incineration yielded Some quantity

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222 PERKIN : A NATURAL SUBSTANTIVE DYESTUFF.

of ash, and appeared to consist of a calcium salt of the colouring matter. The partly evaporated acetone extract, on treatment with a little boiling benzene, deposited a dull ochre-coloured precipitate almost devoid of tinctorial property, which was removed and the filtrate fractionally evaporated. By this means a gradual separa- tion of the colouring matter was effected, the earlier fractions possessing a deep maroon colour, and those obtained later having a beautiful scarlet tint. The final mother liquid contained, together with some quantity of plant wax, a trace of a yellow, resinous compound.

The crude colouring matter redissolved in a mixture of acetone and benzene was again fractionally crystallised as before, the first and final deposits being rejected, and this appeared to be the only method available in dealing with so small a quantity of the sub- stance. The product consisted of a bright red, almost scarlet, powder, which under the microscope appeared as nodules possessing fine, saw-like edges, and thus possessed an ill-defined crystalline structure. The quantity of colouring matter thus isolated was approximately 3 grams, and of this four distinct preparations, dried at 160°, were analysed :

Found, C = 67-27 ; 67.53 ; 67.66 ; 67.40; H = 4-40 ; 4.61 ; 4-73 ; 4.33. CI6Hl2O6 requires C = 67.60 ; H = 4.23 per cent.

It is very readily soluble in alcohol, very sparingly so in boiling water, and dissolves in alkaline solutions with a violetrred colour, which rapidly becomes brown owing to oxidation. It is only partly precipitated by excess of alcoholic lead acetate, forming a dull reddish-violet lake soluble in water, but is completely deposited by means of the basic acetate with formation of an insoluble lead salt. With alcoholic ferric chloride it gives a brown coloration, and its solution in both sulphuric and nitric acid is yellow, the latter acid reacting to form a nitro-compound precipitated by water. It does not contain me thoxy-gr oups.

The colouring matter was fused with potassium hydroxide and a little water to 200-220° for twenty minutes, the brownish-coloured mass dissolved in water, and the solution acidified and extracted with ether. The crystalline residue obtained by evaporating the ether, when examined in the usual way, gave phloroglucinol (m. p. 210O) and an acid, melting at 210°, which had all the properties of p-hydroxybenzoic acid, and could be admixed with it without alteration of melting point. A second experiment gave also a trace of a compound of lower melting point resembling p-hydroxy- acetophenone, but this point requires further corroboration,

Merely a trace of the substance was available for dyeing experi- ments, but this w w sufficient to indicate that the tinctorial

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EDMINSON AND HILDITCH: OPTICAL ACTIVITY. PART IV. 223

properties of the plant were entirely due to this colouring matter. As was to be expected from its behaviour with lead acetate solution, it does not dye mordanted calico, although, as previously indicated, it is a substantive dyestuff towards wool. By the use of a boiling aqueous extract of the plant itself, a dull red shade was obtained with woollen cloth, and this became rather weaker when it was treated with warm dilute soap solution. A very permanent and slightly fuller colour was produced by previously mordanting the wool with chromium or copper: and a similar result could be obtained by an application of the mordant after the dyeing operation. In comparison with the better-known substantive natural dyestuffs, the ‘( red dura ” very closely resembles in this behaviour the ‘‘ insoluble red woods,” which contain as the chief colouring matter santalin, and of which sanderswood (Pterocarpus santalinus) is a typical example. The shades given by the latter, although of a faintly yellower character, closely resemble those produced by the “ red dura,” and although the sanderswood possessed somewhat the stronger dyeing power, there was but a trifling distinction to be observed in this respect. Again, it was ascertained that by submitting sanderswood to a similar process to that described above, the colouring matter thus isolated was very similar in appearance and general properties to that obtained from the ‘(red dura.” It therefore seems appropriate to term this latter dura-santalin.

The formula of santalin, C,,H,,O,(O=CH,) (Cain and May, J. SOC. Chem. Znd., 1909, 28, 697), does not suggest the existence of a simple chemical relationship between these colouring matters, but it seems likely that they may possess in common a special grouping which will account for their close resemblance.

CLOTHWORKERS’ RESEARCH LABOEATOI1Y,

THE UNIVERSITY,

LEEDS.

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