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 dyestuffwas received from the authorities of the Imperial Institute, underthe name of the “ red dura” of the Soudan, the dyeing propertiesof which proved to be specially interesting in that good shadesupon wool could be obtained from it without the aid of a mordant.The material consisted of the leaf sheaths of a, grass, smoothexternally, possessing a deep reddish-brown tint, and approximatelynine inches in length, together with cylindrical fragments of thestem (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 thPERKIN : A NATURAL SUBSTANTlVE DYESTUFF. 221manufacture of coloured ‘ bursh ’ (mats), but occasionally for theleather of ‘ markubs ’ (Sudanese shoes).This durra is speciallygrown for the purpose and not for eating. It occurs in this district,but comes mainly from Rahad, Dinder, and the south.” Theresults of the examination of this product a t the Royal BotanicGardens, 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 theSorghum wulgare, constitutes the “ Great Millet,” the grain ofwhich is so important a foodstuff.An elaborate account of theSorghum vulgare is given by Watt (“Dictionary of the EconomicProducts of India,” Vol. 6, Part 111, p. 289), and it is worthyof note that in certain cases the grain is described as possessing abrick-red colour, and that a t Harihar this is used for preparing ared morocco from goat skin. Again, it is stated in connexion withthe Sorghum saccharaturn that when the pressed canes are allowedto ferment, their colour changes to a red or reddish-brown, andthat the dye thus produced can bs extracted by means ofdilute alkali, and is precipitated from this solution by means ofacid in the form of red flakes. The Indian, Persian, Abyssinian,and Egyptian forms would seem to be derived from the Andropogonsorghum, var.‘ I durrha” (ibid., p. 278)) but the fact that thisplant is so extensively cultivated in Egypt as a foodstuff, whereas,according to Browne (Zoc. cit.), the ‘‘ Sikhytan ” is grown entirelyon account of its dyeing properties, leaves one t o infer that thislatter is again a special variety. Unfortunately, but a few ouncesof this material were available for examination, and this did notpermit of any extended investigation of the colouring matter whichis present, but should it be possible to obtain a large quantity ofthis dyestuff, a more exhaustive study of the subject will then becarried out.Ex P ER IMENTAL.The leaf sheaths and stems (pith) were examined separately,but as experiment showed that the same products were presentin both cases, this was evidently not necessary.The material wasextracted in a Soxhlet apparatus with boiling acetone until nothingfurther dissolved, and by evaporating the deep brownish-colouredextract there was obtained from the sheaths 16-27 per cent., andfrom the pith 14.7 per cent., of a dark brittle resin. On agitatingthis residue with cold acetone, a small quantity of substance didnot. pass into solution, and the operation was repeated until thefinal product was entirely soluble under this treatment. Theamorphous substance thus removed, and which, when dry, possesseda Slight beetle-green lustre, on incineration yielded Some quantit222 PERKIN : A NATURAL SUBSTANTIVE DYESTUFF.of ash, and appeared to consist of a calcium salt of the colouringmatter.The partly evaporated acetone extract, on treatment witha little boiling benzene, deposited a dull ochre-coloured precipitatealmost devoid of tinctorial property, which was removed and thefiltrate fractionally evaporated. By this means a gradual separa-tion of the colouring matter was effected, the earlier fractionspossessing a deep maroon colour, and those obtained later having abeautiful scarlet tint. The final mother liquid contained, togetherwith some quantity of plant wax, a trace of a yellow, resinouscompound.The crude colouring matter redissolved in a mixture of acetoneand benzene was again fractionally crystallised as before, the firstand final deposits being rejected, and this appeared to be the onlymethod 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 possessingfine, saw-like edges, and thus possessed an ill-defined crystallinestructure. The quantity of colouring matter thus isolated wasapproximately 3 grams, and of this four distinct preparations, driedat 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 boilingwater, and dissolves in alkaline solutions with a violetrred colour,which rapidly becomes brown owing to oxidation.It is only partlyprecipitated by excess of alcoholic lead acetate, forming a dullreddish-violet lake soluble in water, but is completely deposited bymeans of the basic acetate with formation of an insoluble lead salt.With alcoholic ferric chloride it gives a brown coloration, and itssolution in both sulphuric and nitric acid is yellow, the latter acidreacting to form a nitro-compound precipitated by water. It doesnot contain me thoxy-gr oups.The colouring matter was fused with potassium hydroxide and alittle water to 200-220° for twenty minutes, the brownish-colouredmass dissolved in water, and the solution acidified and extractedwith ether. The crystalline residue obtained by evaporating theether, when examined in the usual way, gave phloroglucinol (m.p.210O) and an acid, melting at 210°, which had all the propertiesof p-hydroxybenzoic acid, and could be admixed with it withoutalteration of melting point. A second experiment gave also a traceof 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 ww sufficient to indicate that the tinctoriaEDMINSON AND HILDITCH: OPTICAL ACTIVITY. PART IV. 223properties 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 boilingaqueous extract of the plant itself, a dull red shade was obtainedwith woollen cloth, and this became rather weaker when it wastreated with warm dilute soap solution. A very permanent andslightly fuller colour was produced by previously mordanting thewool with chromium or copper: and a similar result could beobtained by an application of the mordant after the dyeingoperation. In comparison with the better-known substantivenatural dyestuffs, the ‘( red dura ” very closely resembles in thisbehaviour the ‘‘ insoluble red woods,” which contain as the chiefcolouring matter santalin, and of which sanderswood (Pterocarpussantalinus) is a typical example. The shades given by the latter,although of a faintly yellower character, closely resemble thoseproduced by the “red dura,” and although the sanderswoodpossessed somewhat the stronger dyeing power, there was but atrifling distinction to be observed in this respect. Again, it wasascertained that by submitting sanderswood to a similar process tothat described above, the colouring matter thus isolated was verysimilar in appearance and general properties to that obtained fromthe ‘(red dura.” It therefore seems appropriate to term thislatter 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 existenceof a simple chemical relationship between these colouring matters,but it seems likely that they may possess in common a specialgrouping which will account for their close resemblance.CLOTHWORKERS’ RESEARCH LABOEATOI1Y,THE UNIVERSITY,LEEDS