DYE I N G purplish brown with iron. Their chief employment is in wooldyeing, for the production of various shades of brown, being best applied by the “stuffing and saddening” method above described ; but since the colours are fugitive to light, they are now very largely replaced by Alizarin. A brown on wool is obtained by first boiling for one to two hours in a decoction of the ground wood (50 per cent.), and then boiling in a separate bath in solution of bichromate of potash (2 per cent.) for half an hour. These dyewoods are also employed by the indigo-dyer, in order to give a brownish ground colour to the wool previous to dyeing in the indigo vat, and thus obtain a deeper, fuller blue. The colouring matters contained in these dyewoods have not been exhaustively examined. Old Fustic is a yellow dyestuff, and consists of the wood of the dyer’s mulberry tree, Morus tinctoria, which grows in Cuba, Jamaica, &c. It is still an important and largely used dyestuff, being cheap, and the colours obtained from it being satisfactorily fast to light and other influences. With chromium mordant it yields an olive-yellow or “old-gold” shade; with aluminium, yellow ; with tin, a brighter yellow ; with iron, an olivegreen. It is chiefly employed in wool-dyeing along with other dyestuffs, and furnishes the yellow in compound shades. Two colouring principles exist in Old Fustic, namely, morin and maclurin, the former being the most important, and generally regarded as the true colouring matter. Young Fustic consists of the wood of the sumach tree, Rhus cotinus, which grows in Italy and Southern Europe. Its general dyeing properties are similar to those of Old Fustic, although the various mordants give somewhat different colours, notably the tin mordant, which gives a brilliant orange-yellow. All the colours obtained are very fugitive to light, hence this dyestuff is now of little importance. The colouring matter of Young Fustic is called fisetin. Quercitron Bark consists of the inner bark of an oak-tree, Quercus tinctoria, which grows in the North American States. It dyes somewhat like Old Fustic, but gives with aluminium and tin mordants brighter yellows, for which colours it is chiefly used. The colouring principle of Quercitron Bark is called quercitrin, which by the action of boiling mineral acid solutions is decomposed, with the production of the true colouring matter termed quercetin. So-called Flavine is a commercial preparation of Quercitron Bark consisting of quercitrin or of quercetin ; it is much used by wool-dyers for the production of bright yellow and orange colours. Wool is dyed in single bath by boiling with a mixture of Flavine (8 per cent.), stannous chloride (4 per cent.), and oxalic acid (2 per cent.). Flavine is used in small quantity along with cochineal for dyeing scarlet on wool. Persian Berries are the dried unripe fruit of various species of Rhammis growing in the Levant. The general dyeing properties are similar to those of Quercitron Bark, the orange colour given with tin mordant being particularly brilliant. The high price of this dyestuff causes its employment to be somewhat limited. The colouring matter of Persian Berries is called xanthorhamnin, which by the action of fermentation and acids yields the true dyestuff rhamnetin. Weld is the dried plant Reseda luteola, a species of wild mignonette, formerly largely cultivated in Europe. Its dyeing properties resemble those of Quercitron Bark, but the yellows with aluminium and tin mordants are much brighter and purer, and also faster to light. It is still used to a limited extent for dyeing a bright yellow on woollen cloth and braid for the decoration of military uniforms. Quite recently the colouring matter of Weld, namely, luteolin, has been prepared artificially, but the process is too expensive to be of practical use. Logwood is the heart-wood of Hcematoxylon campechianum, a tree growing in Central America. It is the most important natural dyewood at present employed, being largely used for dyeing dark blues and black on silk, wool, and cotton. With chromium and aluminium mordants logwood dyes a dark blue, and even black ; with tin, a dark purple; and with iron, black. The colours are only moderately fast to light. On wool the mordant is bichromate of potash, on cotton and silk an iron mordant is employed. Before use by the dyer the logwood is ground and aged or oxidized, by allowing moistened heaps of the ground wood to ferment slightly, and by frequently turning it over to expose it freely to the air. By this means the colouring principle hasmatoxylin which logwood contains is changed into the true colouring matter hsemateiin. The constitution of this colouring matter has been recently discovered ; it is very closely allied to the brazilin of Peachwood, Sapanwood, and Limawood, and is also a member of the 7-pyrone group of colouring matters. The importance of the above-mentioned natural dyestuffs is gradually diminishing in favour of mordant dyestuffs and others derived from coal-tar. Old Fustic and Logwood are perhaps the most largely used, and may continue to be employed for many years, owing to their comparatively low price.
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The Artificial Mordant Colours are well represented by Alizarin, the colouring matter of the Madder root, which was the first natural dyestuff prepared artificially in 1868 from the coaltar product anthracene. For this reason many of these colours are frequently referred to as the Alizarin Colours. At the present time, however, there are numerous Mordant Colours which are prepared from other initial materials than anthracene ; they are not chemically related to Alizarin, and for these the term Alizarin Colours is therefore inappropriate. The property, which Mordant Colours possess in common, of combining with metals and producing lakes, which readily adhere to the fibre, depends upon their chemical constitution, more particularly upon the general and relative position in the molecule of certain side atomic groups. In Alizarin there are, for example, two characteristic hydroxyl groups (OH) occupying a special (ortho) position in the molecule —i.e., they are next to each other, and also next to one of the so-called ketone groups (C : 0). In other Mordant Colours there are carboxyl (COOH) as well as hydroxyl groups, which are allimportant in this respect. In addition to this, the general dyeing property is influenced by the constitution of the molecule itself, and by the presence of other side-groups, e.g., NH2, HSO:i, &c., which modify the colour as to solubility or hue. Hence it is that the members of this group, while possessing the mordant-dyeing property in common, differ materially in other points. Some, like Alizarin, are not in themselves to be regarded as colouring matters, but rather as colouring principles, because they only yield useful dyes in combination with metallic oxides.. According to their constitution, these may yield one or many colours with the various metallic oxides employed, and they are used for cotton as well as for wool and silk. Other Mordant Colours, e.g., many of the Direct Colours and others, are capable of dyeing either the vegetable or animal fibres without the aid of a mordant; they are fully developed colouring matters in themselves, and possess the mordant dyeing property as an additional feature, in consequence of the details of their chemical constitution, to which reference has been made in the foregoing paragraphs. As a rule these yield, at most, various shades of one colour with the different oxides, and are only suitable for the animal fibres, particularly wool. In the following list, the most important artificial Mordant Colours are arranged according to the colour they give in conjunction with the aluminium mordant, unless otherwise indicated. Those which dye the animal fibres, even without mordants, are given in italics ; some are Direct Colours possessing mordant-dyeing properties, others are sulphonic acid derivatives of Alizarin Colours, suitable for wool but not for cotton. Red. —Alizarin, Anthrapurpurin, Flavopurpurin, Purpurin, Alizarin Bordeaux, Alizarin Garnet R, Alizarin Maroon, Alizarin S, Cloth Red, Diamine, Fast Red, Anthracene Red. Orange and Yellow.—Alizarin Orange, Alizarin Orange G, Alizarin Yellow paste, Alizarin Yellow A, Alizarin Yellow C, Anthracene Yellow, Galloflavin, Fustin, Alizarin Yellow GG, Alizarin Yellow R, Diamond Flavin G, Chrome Yellow D, Crumpsall Yellow, Fast Yellow, Diamond Yellow, Renzo Orange R, Cloth Orange, Carhazol Yellow, Chrysamine. Green.—Ccerulein, Coerulein S, Alizarin Green S, Fast Green (Fe), Naphthol Green (Fe), Dioxin (Fe), Gambine (Fe), Azo Green, Gallanil Green, Alizarin Green G and B, Acid Alizarin Green, Alizarin Cyanine Green, Diamond Green. Blue.—Alizarin Blue, Alizarin Blue S, Alizarin Cyanine, Anthracene Blue, Brilliant Alizarin Blue, Alizarin Indigo Blue S, Acid Alizarin Blue, Brilliant Alizarin Cyanine, Alizarin Saphirole, Gallanilide Blue, Delphine Blue, Gallamine Blue, Celestine Blue, Chrome Blue, GoMazine A, Phenocyanine, Coreine. Purple and Violet.—Gallein, Gallocyanine, Chrome Violet. Brown.—Anthracene Brown, Chromogen, Cloth Brown, Diamond Brown, Alizarin Brown, Fast Brown. Black.—Alizarin Black, Diamond Black, Alizarin Blue Black, Alizarin Cyanine Black, Alizarin Fast Grey, Chromotrope. A brief description of the application of a few of the more important of the above colouring matters will suffice. Alizarin, Anthrapurpurin, and Flavopurpurin give somewhat similar shades with the different mordants, namely, brown with chromium, red with aluminium, orange with tin, and purple with iron mordant. « In wool-Ayemg they are applied along with other Mordant Colours on chromium mordant for the production of a large variety of compound shades, browns, drabs, greys, &c., the presence of acetic acid in the dyebath being advantageous. When alum, and tartar mordant is employed, for the production of reds, it is necessary to add a small amount (4 per cent.) of calcium acetate to the dyebath, in order to neutralize the strong acidity of the mordanted wool, and to furnish the calcium of the colour-lake fixed upon the fibre, which is regarded as an aluminium-calciuni compound of the colouring matter. S. III.— 71
