DYE-STUFFS (FR., Matieres tinctoriales ; GEE., Fiirbematerialien), The term " dye-stuffs " is commercially employed to designate collectively the plants, flowers, licbens, woods, roots, exudations, and other products yielded by the vegetable kingdom, which are used in dyeing, printing, staining, and colouring.
Until within very recent times, these substances formed one of the most considerable items of our import trade, and were essential to the existence of our textile industries ; but the modern introduction of compounds derived from coal-tar—containing the same colouring principles in an artificial form, or replacing them by others, equally, and often more, brilliant and permanent,—and the cheapness and abundant supply of these manufactured substitutes, have had a meet disastrous and lasting effect upon a once flourishing and important branch of commerce. The deleterious nature of some of the coal-tar colours is at present confining their use within comparatively narrow limits, and this may yet continue for a few years ; but it seems impossible to doubt that the old fashioned dye-stuffs will, in the near future, be almost entirely replaced by the cheaper chemical preparations, at least in those countries where the latter are largely produced.
Alkanet (Fs., Orcanite ; GER., Orkanet).—The root of Anchusa (Alkanna) tinctork contains a dark blood-red resinous principle termed "Anchusin," or "Alkanna red," obtained by exhausting the root with alcohol, evaporating, and shaking up with ether. The resin is insoluble in water, but readily soluble in alcohol, and better still in ether, oils, and bisulphide of carbon, to all of which it communicates a purple-red colour; in concentrated sulphuric acid, it gives amethyst ; in alkalies, blue ; from the last, it is precipitated by acids, in brown-red flocks. It is used chiefly in pharmacy, to colour medicines ; in perfumery, to colour oils and greases ; to colour lime-wash, for application to walls; and with oils, to stain woods in imitation of rosewood. In China, it is used chiefly for colouring candles, and medicinally. The plant grows in sandy places in the Mediterra nean basin, and is occasionally cultivated in Languedoc, and the Levant. Small quantities are met with in commerce, and valued at about 30s. a cwt.
Aloes (see Drugs).—From aloes, has been produced a yellow dye, termed " cbrysammic sold." It is prepared by heating in a water-bath 8 parts nitric acid with 1 part aloes ; when violent action has ceased; a second part of the latter is added ; heating is continued till no more hypouitric fumes are evolved. The mass is then poured slowly into abundance of water ; chrysammic acid flakes settle at the bottom of the vessel ; they are washed with water, till the latter assumes a fine colour. The acid occurs as small golden-yellow scales, soluble in alcohol and ether, sparingly in cold water, readily in boiling water. The acid is a pure polychrome, changing its colour according
to circumstances. It has long been known as giving a beautiful purple to silk, black to wool, and pink to linen. A French firm have recently used it to produce a fine brown, named " vegetable brown," which consists in applying the acid in conjunction with sulphuric acid—say 45 parts of the former to 6-8 parts of the latter. The dye is bright; it resists the strongest alkaline milling ; it combines with most of the aniline and other dyes, economizing them, and rendering them thoroughly fast ; and it is not expensive.
Annatto, or Arnotto (Fn., Arnotto, Rocou ; GER., Arnotto, Orlean). — The seeds of Bixa orcllana are enveloped by a soft resinous pulp, of vermilion colour, and unpleasant odour, known in the French Colonies as rocou, and in other parts of S. America as achiote. The plant grows in Africa, the E. and W. Indies, and S. America; it is cultivated chiefly in Guadaloupe, Cayenne, and Martinique, sparingly in Mexico and Brazil. There are several ways of preparing the dye : (1) The pulp and seeds are treated with hot water, left to macerate in the presence of an antiseptic, and separated by pounding with a wooden pestle ; the seeds are strained off, the pulp is left to settle, the water is decanted, and the colouring matter, in a pasty condition, is exposed in shallow vessels to dry gradually in the shade. When sufficiently consistent, it is made into rolls or balls of 2-3 oz., and dried in an airy place. (2) The entire ripe fruit is coarsely crushed, treated with hot water, and soaked for several days ; the seeds are then strained off, and the pulp is left to ferment for about a week ; the water is poured off, and the dye-stuff is dried in the shade till it can be made up in cakes of 3-20 lb., and covered with banana leaves. This is known as " flag annatto " ; it is inferior to (3), owing to the fermentation. The fresh article contains about 5} per cent. of colouring matter and over 70 per cent. of water. (3) The Indians adopt a laborious process :—they rub the fruit with oiled hands, till the pulp is separated, and reduced to a clear paste ; this is scraped off the hands, and laid on leaves to dry in the shade. The product is very superior. The three French Colonies of Cayenne, Guadalonpe, and Martinique have about 6000 acres of land under culture with annatto, and produce yearly about 3 million lb. The supply now exceeds the demand. In dyeing and printing, it is now largely superseded by rosolic acid (see p. 680), though still retained for low-class cotton yarns, and for modifying the shades of ether dyes. The tablets prepared by the first process are used in Dutch, American, and English dairies, for colouring butter and cheese. Our annual imports of "roll " annatto are about 1000 cwt. ; and of " flag," 3000 cwt. The former is worth about 21.-9d. a lb.; the latter, 5d.-18. 6d.