364 MOBINDA CITBIFOLIA 



operation is by no means complete ; nay, what remains to be done is not the least 

 important to success, nor the least delicate of execution. Let us bear in mind that 

 the mordant is intended to combine not only with the organic fibre, but afterwards 

 also with the colouring-matter, and that, consequently, it must be laid entirely bare, 

 or scraped clean, so to speak, that is, completely disengaged from all foreign sub- 

 stances which might invest it, and obstruct its intimate contact with the colouring- 

 matters. This is the principle and the object of two operations, to which the names 

 of dunging and clearing have been given. See CALICO-PRINTING. 



If the mordant applied to the surface of the cloth were completely decomposed, and 

 the whole of its base brought into chemical union with it, a mere rinsing or scouring 

 in water would suffice for removing the viscid substances added to it but this never 

 happens, whatsoever precautions may be taken ; one portion of the mordant remains 

 untouched, and besides, one part of the base of the portion decomposed does not enter 

 into combination with the stuff, but continues loose and superfluous. All these par- 

 ticles, therefore, must be removed without causing any injury to the dyes. If in this 

 predicament the stuff were merely immersed in water, the free portion of the mordant 

 would dissolve, and would combine indiscriminately with all the parts of the cloth not 

 mordanted, and which should be carefully protected from such combination, as well as 

 the action of the dye. We must therefore add to the scouring-water some substance 

 that is capable of seizing the mordant as soon as it is separated from the cloth, and of 

 forming with it an insoluble compound ; by which means we shall withdraw it from 

 the sphere of action, and prevent its affecting the rest of the stuff, or interfering with 

 the other dyes. This result is obtained by the addition of cow-dung to the scouring- 

 bath : a substance which contains a sufficiently large proportion of soluble animal 

 matters, and of colouring particles, for absorbing the aluminous and ferruginous salts. 

 The heat given to the dung-bath accelerates this combination, and determines an in- 

 soluble and perfectly inert coagulum. 



Thus the dung-bath produces at once the solution of the thickening paste ; a more 

 intimate nnion between the' alumina or iron and the stuff, in proportion to its eleva- 

 tion of temperature, which promotes that union ; an effectual subtraction of the unde- 

 composed and superfluous part of the mordant, and perhaps a commencement of 

 mechanical separation of the particles of alumina, which are merely dispersed among 

 the fibres ; a separation, however, which can be completed only by the proper scour- 

 ing, which is done by the dash-wheel with such agitation and pressure (see BLEACHING) 

 as vastly facilitate the expulsion of foreign particles. 



Before concluding this article, we may say a word or two about astringents, and 

 especially gall-nuts, which have been ranked by some writers among mordants. It is 

 rather difficult to account for the part which they play. Of course we do not allude 

 to their operation in the black dye, where they give the well-known purple-black 

 colour with salts of iron ; but to the circumstance of their employment for a variety 

 of dyes, and also of dye-drugs, as sapan and Brazil-wood, madder, and logwood, and 

 especially in the dye Adrianople or Turkey red. All that seems to be clearly estab- 

 lished is, that the astringent principle or tannin, whose peculiar nature in this 

 respect is unknown, combines like mordants with the stuffs, and fixes a greater 

 quantity of the base upon it, and thus adds depth to the colour, as well as certain 

 peculiarities of tint ; but as this tannin has itself a brown tint, it will not suit 

 for white grounds, though it answers quite well for pink grounds. When white 

 spots are desired upon a cloth prepared with oil and galls, they are produced by an 

 oxygenous discharge, effected either through chlorine or chromic acid. See CALICO- 

 PHINTING, and the various MOHDANTS there particularised under their respective 

 heads. J. N. 



MOREEN. A stout woollen stuff, which is chiefly employed for curtains. 



1WORINDA CITRXFOXiXA. This was first imported into Glasgow, from 

 India, some years ago. It occurs in pieces of from 2 to 8 centimeters in length, and 

 from 5 to 10 millimeters thick. Externally it is brown, internally yellow : the pig- 

 ment, or colouring-matter, is exclusively concentrated in the bark ; its colour is 

 orange-yellow, and it has been named morindin. 



The morindin is extracted from the root by exhausting with boiling alcohol: mi 

 cooling, the colouring-matter is deposited as an impure flocculent material, mixed 

 with a red substance. This crude material is purified by repeated re-crystallisation, 

 first from alcohol at 50 per cent., and finally from stronger alcohol acidulated with 

 hydrochloric acid. Thus obtained, the substance forms satin-like, needle-shaped, 

 yellow crystals. Morindin is sparingly soluble in cold water, more readily in boiling, 

 but is deposited, on cooling, as a gelatinous mass. It is sparingly soluble in alcohol 

 when cold, but readily when boiling, and best in a weaker spirit ; it is insoluble in 

 ether. The aqueous solutions are coloured orange by alkalis ; lime- and baryta-water 

 yield red precipitates ; while acetate of lead forms a crimson precipitate ; a mixture of 



