166 MADDER 



inferred that the insoluble red colouring-matter was simply a product of oxidation of 

 the soluble yellow one, and that, consequently, the more complete the exposure of the 

 triturated root to the atmosphere, the greater would be its tinctorial power ; and he 

 even went so far as to assert that all the proximate principles obtained from the root 

 were derived ultimately from one single substance contained in the whole plant. That 

 the fresh roots, before being dried, do indeed contain no colouring-matter capable of 

 imparting to mordants colours of the usual appearance and intensity, may be proved 

 by the following experiment : If the roots, as soon as they are taken out of the 

 ground, are cut into small pieces as quickly as possible, and then extracted with 

 boiling spirits of wine, a yellow extract is obtained, which, after being filtered and 

 evaporated, leaves a brownish-yellow residue. Now this residue, on being redissolved 

 in water, is found incapable of imparting to mordants any but the slightest shades 

 of colour ; and, on the other hand, the portion of the root left after extraction with 

 spirits of wine, on being subjected to the same test as the extract, is found to possess 

 as little tinctorial power as the latter. If, however, the roots, instead of being treated 

 with spirits of wine, are macerated in water, the liquor, on being gradually heated, 

 dyes the usual colour as well as ordinary madder. Hence it may be inferred that by 

 means of alcohol the colour-producing body of the root may be separated from the 

 agent which, under ordinary circumstances, is destined to effect its transformation 

 into colouring-matter, the one being soluble and the other insoluble in that menstruum. 

 It was by this and other similar facts that Schunck was led to an examination of this 

 part of the subject. He infers from his experiments that the colour-producing body 

 of maddder is identical with its so-called bitter principle, to which he has given the 

 name of Rubian. This body, when pure, has the following properties : It is an 

 amorphous, shining, brittle substance like gum, dark brown and opaque in mass, but 

 yellow and transparent in thin layers. Its solutions are of a deep-yellow colour, and 

 have an intensely-bitter taste. It is easily soluble in water and alcohol. The watery 

 solution turns of a blood-red colour on the addition of caustic and carbonated alkalis, 

 and gives dark-red precipitate with lime and baryta-water. The solution gives a 

 copious light-red precipitate with basic acetate of load, but yields no precipitate with 

 any other metallic salt. On trying to dye with rubian in the usual manner, the mor- 

 dants assume only the faintest shades of colour. If, however, the watery solution be 

 mixed with sulphuric or muriatic acid and boiled, it gradually deposits a quantity of 

 insoluble yellow flocks, which, after being separated by filtration and well washed, 

 are found to dye the same colour as those obtained by means of madder. In fact, 

 these flocks contain alizarine, to which they owe their tinctorial power, but they also 

 contain a crystallised yellow colouring-matter, similar to, but not identical with, 

 rubiacine, as well as two resinous colouring-matters, which Schunck has named 

 Verantine and Rubiretine, and which are probably identical with the resinous 

 colouring-matters before referred to as being obtained from ordinary madder. The 

 liquid filtered from the flocks contains an uncrystallisable sugar, similar to that which 

 is obtained from the madder itself. Rubian is not decomposed by ordinary ferments, 

 such as yeast and decomposing-casein ; but by extracting madder with cold water, 

 and adding alcohol to the extract, a substance is precipitated in pale-red flocks, which 

 possesses in an eminent degree the power of effecting the decomposition of rubian. If 

 a watery solution of the latter be mixed with some of the flocculent precipitate 

 (after having been collected on a filter, and washed with alcohol), and then left to 

 stand in a warm place for some hours, the mixture is converted into a light-brown 

 jelly, which is so thick that the vessel may be reversed without its falling out. This 

 jelly, when agitated with cold water, communicates to the latter very little colour or 

 taste, proving that the rubian has undergone complete decomposition by the action of 

 the flocculent substance or ferment added to its solution. The cold water, however, 

 extracts from the gelatinous mass a quantity of sugar, while the portion left undis- 

 solved contains alizarine, verantine, rubiretine, and a crystalline yellow colouring- 

 matter, besides a portion of undecomposed ferment. Rubian, therefore, by the action 

 of strong mineral-acids and of the peculiar ferment of madder, is decomposed, yielding 

 sugar and a variety of colouring-matters, the principal of which is alizarine. It appears, 

 therefore, that these colouring-matters are not originally contained as such in the root, 

 but are formed by the decomposition of one parent substance, which alone is produced 

 by the vital energies of the plant. In addition to this substance, the plant also con- 

 tains another, which possesses the property of rapidly effecting the decomposition of 

 the first. The two are, however, during the living state of the plant, prevented from 

 acting on one another, either in consequence of their being contained in different cells, 

 or because the vital energies of the plant resist the process of decomposition. During 

 the drying and grinding of the root the decomposition of the colour-producing body 

 commences and continues slowly during the period that the powder is kept before 

 being used. It is finally completed during the process of dyeing itself, and hence no 



