Among the first records of the human race are frequent intimations of an appreciation of the brilliant hues displayed by natural objects, and means were early found of appropriating them for the adornment of personal apparel. To the fine linen were transferred the brilliant blue, scarlet, and purple hues extracted from vegetable or animal substances, the last named color reserved exclusively for the vestments of kings and high priests. The skins of the ram and the badger used by Moses for the tabernacle were dyed red, and in his time the art of coloring woollen purple was already known. The Tyrians early attained a high perfection in the art, and their king sent to Solomon a man skilful to work " in purple and blue, and in fine linen and in crimson." Along the coast of Phoenicia they found the two kinds of shellfish called by Pliny the buccinum and purpura, and from them they extracted a juice which caused their name to be ever associated with the rich purple dye. In such estimation was this held in the time of the Roman emperors, that a pound weight of the cloth which had been twice dipped in it was sold, as Pliny states, for a sum equal to about $150. But its use being restricted to the emperors, the art of preparing it was at last lost.

It was revived in the 17th and 18th centuries in England and France, but better colors and cheaper processes were then in use. The discoverers and early conquerors of the countries of North and South America were astonished by the skill exhibited by the Peruvians and Mexicans in the application of numerous beautiful dyes extracted from forest trees. According to Pliny, the methods of dyeing black, blue, yellow, and green were brought into Greece on the return of the expedition of Alexander the Great from India, where it appears that the art of coloring cotton cloths with rich and permanent dyes had long been known and practised. The Venetians and Genoese in the height of their prosperity, in the time of the crusades, transferred the art to Italy; and Florence in the early part of the 14th century, it is said, contained 200 dyeing establishments. The important dyestuff archil was discovered about the year 1300 by a merchant of Florence. In the 15th century a work upon dyeing was published in Venice, of which subsequent editions were issued down to 1548, containing full details of the processes employed. From this work it appears that the use of indigo was unknown in Europe at the latter date, though in India it was probably an important article in dyeing at the remotest periods.

It was afterward introduced from America together with cochineal, logwood, annotto, quercitron, Brazil wood, and other dyes; but its use in England and Saxony, as of logwood also, met with the most determined opposition. The cultivators of the woad then in use for dyeing blue caused decrees to be issued against indigo as a most dangerous product. By the German diet in 1577 it was declared to be "a pernicious, deceitful, eating, and corrosive dye;" and the name was given it of food for the devil. An act of parliament in the reign of Elizabeth forbade its use, and authorized the destruction of it and of logwood wherever found, and this continued in force for nearly a century. About the year 1630 it was discovered that the crimson color obtained from cochineal might be converted into a brilliant scarlet by the application of a salt of tin. The introduction of this metal as an occasional substitute for alum as a mordant is attributed to a dyer named Cornelius Drebbel. The use of pure mordants marks the great improvement of the art in modern times, as also the introduction of a great variety of new dyes obtained from mineral substances.

The Flemings during the 17th century carried the skill to which they had attained in this art into Germany, France, and England. After them the French directed particular attention to it, and men of eminence in chemical science, as Du Fay, Hellot, Macquer, and Berthollet, were appointed by the government to investigate and perfect the processes. The method practised in the East of giving to cotton the beautiful and permanent Turkey red dye was made known in their publications, and the art was about the same time introduced into France by some Greek dyers. The business was afterward permanently established at Glasgow by a Frenchman named Papillon. - The art of dyeing consists in the application of colors, principally organic, to animal or vegetable fibre or fabrics, such as silk, woollen, linen, or cotton. Some colors possess the property of uniting with the fibre without the intervention of any other body, the coloring matter being immediately taken up and retained in an insoluble state; such are called substantive colors. Others require the presence of another substance called a mordant, which furnishes a base for the coloring matter to unite with, and which also acts upon the fibre in such a way as to cause the insoluble dye to adhere more closely; these are called adjective colors.

The materials also which are to be dyed have different powers of absorbing and retaining coloring matters; wool and silk possessing a greater facility in this respect than cotton or linen. Wool requires much less preparation than cotton to fit it to receive dyes, either with or without the use of mordants, it being only necessary to cleanse it from a fatty substance called the yolk, which is done by scouring it in a weak alkaline solution. The natural varnish which covers the fibre of silk does not prevent it from absorbing the dye, it being only necessary to rinse it in soap lye at a moderate temperature; but to remove the varnish boiling in an alkaline solution is usually practised. The dyeing substance must be applied in a state of solution, that the fibres of the material to be dyed may imbibe it. If, however, it remains in the fibre in a soluble state, it does not constitute a true dye, this term being only applied to a color which is retained as an insoluble precipitate. A color that may be washed out with warm soap suds or a weak alkaline solution is called a fugitive color; and one which will resist the action of these agents is called a fast color.

Coloring matter may be fixed within a fabric by three methods: 1. By dissolving the dye in some material which being afterward abstracted will leave it in an insoluble state as regards ordinary solvents, such as soap suds and weak alkaline or acid solutions. If a cloth is stained with a solution of oxide of copper in aqua ammonia, the evaporation of the ammonia will leave the oxide of copper deposited in an insoluble state in and upon the fibre. The deposition in an insoluble condition of several coal-tar colors from alcoholic solutions is another instance of this mode of dyeing. 2. The coloring matter may be rendered insoluble by subjecting the material stained with it to the action of warm air, a process called ageing. Such is the case with indigo, quercitron, sumach, and fustic. The oxidizing process may also be accomplished by adding some oxidizing material, as when cloth is dyed black with logwood and chromate of potash, the haematoxyline of the wood being oxidized and chromic acid reduced to chromic oxide; or when aniline black is produced by the action of chlorate of potash, ferrocyanide of potassium, or chromate of copper upon aniline oil. 3. The coloring matter may be precipitated by the use of a mordant, and this is the most important as well as the most common method.

A mordant, strictly speaking, is a solution of some substance which, not being itself a dye, has an affinity for the material to be dyed as well as for the coloring matter of the dyestuff, so that by its means the precipitate will be more firmly fixed upon and within the fibre. Organic coloring matters are generally more firmly fixed than inorganic by the use of mordants. A color is often produced upon a fabric by using two metallic salts whose double decomposition produces an insoluble compound, as for instance the formation of Prussian blue by the action of hydro-ferrocyanic acid upon a salt of iron, or the production of chromate of lead by using chromate of potash and a soluble lead salt. These latter substances when used in this way are considered by some as not being strictly mordants, but they can hardly be placed in any other category with convenience. The following are the more important mordants: alum; sulphate, acetate, and hyposulphite of alumina; aluminate and stannate of soda; chloride of tin; acetate of iron; fatty substances, as Gal-lipoli oil in Turkey red dyeing; albumen, gluten, and caseine. Tannin is used in some cases as a mordant for madder and aniline colors, and for some metallic salts.

Most dyes of organic origin can only be fixed by the use of mordants, but the original color may be much modified by these agents. With alumina compounds madder yields red, pink, and scarlet; with salts of iron, according to the degree of concentration, lilac, purple, and black. Dyed goods are often brightened by passing them through weak acid or alkaline solutions, soap suds, bran bath, or some other dye material. If a piece of cotton stuff is simply stained with a decoction of logwood, the color may be readily washed out with pure water. If, however, it is first dipped in a solution of proto-sulphate of iron and afterward washed, it will be found stained, a portion of the iron having been converted, either by the action of the air or of the fibre, into insoluble oxide. If the cotton is now dipped into a decoction of logwood, the coloring matter of the latter will combine with the oxide of iron within and upon the fibre, and form a color which cannot be removed by washing in water. If the cotton is dipped in the sulphate of iron solution and not washed, but passed through an alkaline solution, so that the alkaline base may abstract the acid from the iron salt, a much greater quantity of oxide of iron will be formed within and upon the fibre, and a greater depth of color will be given to it by subsequent immersion in the decoction of logwood.

When a solution of sulphate of iron and a decoction of logwood are added to each other, the same insoluble coloring matter will be precipitated in the mixture that was formed by bringing the two solutions together in the fabric. If cotton be now immersed in the mixture, it may be feebly stained, but can hardly be said to be dyed. If, however, a piece of woollen be placed in it, it will become strongly dyed. The precipitates which are formed by the combination of the decoctions of dyestuffs, or the pure coloring matters obtained from them with the bases of certain salts, are called lakes. The salts which are principally used for this purpose are those of aluminum and tin, because, their oxides being colorless, the lakes take the tints of the coloring matters. The lakes obtained with the use of iron salts have a different hue from the original coloring matters, being generally duller. In the salts of aluminum, tin, and iron, the base and acid are not held together by a very strong affinity, and consequently their separation by the attraction of the coloring matter for the base is easily effected; but the acetates are more readily decomposed than the corresponding sulphates, and therefore a mixture of alum with acetate of lead is often used as a mordant.

Heat is employed in many cases to facilitate chemical action in dyeing, the solution of salt and coloring matter sometimes remaining together in the cold state without producing a precipitate, where boiling will at once cause it to appear. Sometimes the precipitation is effected by the addition of another substance; thus when a mixture of a solution of alum with certain coloring matters remains clear, a precipitate is formed by the addition of an alkali, which, taking the sulphuric acid from the alum, leaves the alumina to combine with the coloring matter. The principal use of mordants is therefore to form insoluble lakes; but the number of substances that can be used as mordants is much less than of those which may be used for making lakes, on account of the action which some of them have upon the fibre, as well as the influence of the fibre upon their action. The tendency of aluminum, tin, and iron salts to become basic, and of their bases to unite with coloring matters, is what renders them so well adapted to the dyer's art. A cloth to which a mordant has been applied requires before it is dyed to have a certain amount of the mordant fixed within its fibre, and the remainder removed.

Fixing the mordant (ageing) is principally accomplished by heat, which promotes the separation of the base from the acid. It was formerly effected with cotton goods by hanging them up after mordant-ingin a warm room; but now it is more quickly performed by combining the action of moisture with that of heat. An excessive consumption of coloring matter is avoided by the removal of superfluous mordant; and in the case of printed goods this is necessary to prevent the spreading of the color over the unprinted portions of the surface. - Wool may be dyed in the fleece, in the yarn, or in the cloth. It is usual, for fast colors, to mordant the goods with a solution of alum and cream of tartar; or the latter salt may be used with chloride of tin or with sulphate of iron, the selection depending upon the color which may be desired. For dyeing wool blue the best material is indigo, as it yields the finest and fastest color. This substance is not ready formed in the plants from which it is obtained, but is generated by exposing the juice to the action of the air. It is technically called indigotine, and sometimes oxidized indigo, and is precisely the same substance which exists in the dyed cloth and gives it its color.

That it may be deposited in the fibre it is, however, necessary to reduce it to a soluble condition. This is effected by what has been termed deoxida-tion, but which is more strictly the absorption of hydrogen, as will presently be explained. Soluble indigo, called indigogene, is white, and soluble in alkaline liquors; but upon exposure to the air it parts with the hydrogen which had been absorbed, and again becomes indigotine or blue indigo. It was thought by Che-vreul that the juice of the living plant contained indigo white, but this idea cannot be maintained in the light of the fact that white indigo is only soluble in alkaline liquids, whereas the juices of plants are acid. Moreover, the investigations of Schunck show that the organic substance in the living plant which is converted into indigo by fermentation is different from indigo white; he has named it indi-can. (See Indigo.) The process of dyeing wool with indigo is accomplished in what are called blue vats, the formation of which differs somewhat in different countries.

The German vat, which is very manageable, and may be used for two years by merely replenishing, is composed as follows: To 2,000 gallons of water, heated to 130° F., are added 20 lbs. of crystals of common carbonate of soda, 2 1/2 pecks of bran, and 12 lbs. of ground indigo. The mixture being well stirred, fermentation commences in about 12 hours, the liquid assuming a green color. There are then added 2 lbs. of slaked lime, and the vat is again heated and covered for 12 hours longer, when about the same quantities of soda, bran, and indigo, with some lime, are again added. The vat is ready to be worked in about 48 hours after the commencement. It is usual also to add five or six pints of molasses to promote fermentation. ♦ Should this become too active, it is repressed by the addition of more lime; and if it is not active enough, more bran and molasses are added. The bran and molasses are called reducing agents, because the fermentation which they undergo decomposes a portion of the water, abstracting the oxygen, while the hydrogen is taken up by the insoluble indigotine, or blue indigo, C16H10N2O2, which is thus converted into white indigo, or indigogene, C16H12N2O2, which is soluble in alkaline solutions, but not in pure water.

The dyeing is performed by suspending the fabric on frames and moving it about in the vat for about two hours. It is then washed with water and treated with very dilute hydrochloric or sulphuric acid, to remove the alkali. In England blue vats for wool are made with water 500 gallons, indigo 20 lbs., carbonate of potash 30 lbs., bran 9 lbs., madder 9 lbs. The water is heated to just below the boiling point, and the potash, bran, and madder are put in first, and then the indigo, which in all cases should be previously very finely ground. Cold water is added to reduce the temperature to 90° F., which is maintained constantly by a steam pipe. The ingredients are well stirred every 12 hours, and the vat is ready to be worked in 48 hours. It cannot, however, be used for more than a month, and is also more expensive than the German vat, on account of the potash. For dyeing cotton goods, especially if they are heavy, the German vat is used with advantage; but most calicoes are dyed with the cold lime and copperas vat, which is made with 900 gallons of water, 60 lbs. of green copperas, 36 lbs. of ground indigo, and 90 lbs. of slaked lime, stirred every half hour for three or four hours, then left 12 hours to settle and stirred again, when it is ready for dyeing.

The reactions are the formation of sulphate of lime and protoxide of iron, which latter body, by reason of its affinity for oxygen, removes this from a portion of the water, leaving the hydrogen to unite with the blue and form white indigo, which is soluble in the excess of lime. For dyeing Saxony blue sulphindigotic acid is employed, a substance formed by the action of concentrated sulphuric acid on indigo. It is made by treating one part of indigo with about five parts of fuming sulphuric acid. The solution is then poured into a vessel containing water, and in this the wool is immersed for 24 hours, when there will be formed upon it insoluble sulphindigotate of alumina. Wool is dyed with Prussian blue by immersing it in a solution of persulphate or pernitrate of iron and then passing it through a solution of ferro-cyanide of potassium acidulated with sulphuric acid, by which brilliant, blue, insoluble ferro-cyanide of iron, or Prussian blue, is formed. Wool is generally dyed yellow with weld, fustic, or quercitron bark. The yellow coloring matter of weld, luteoline, is extracted by boiling water, to which sometimes caustic lime or alkalies are added to increase the solvent power. Luteoline dissolves with a deep yellow color in caustic alkalies and alkaline carbonates.

Its aqueous extract yields beautiful yellow precipitates with alum, chloride of tin, and acetate of lead. Alum and cream of tartar are generally used together as the mordant for this color. The use of weld for wool dyeing has been abandoned in England, but is retained on the continent, and is also largely used there in silk dyeing. It has only about one fourth the tinctorial power of quercitron, which has so greatly superseded it. Fustic or yellow wood is generally considered the most suitable material for working with other colors, and is therefore extensively used. Quercitron bark has, however, more tinctorial power, and is largely used. Either dyestuff is made into a decoction with boiling water, and the goods are mordanted with alum, to which there is sometimes added chloride of tin, which increases the brilliancy of the color. Wool is dyed red with cochineal, with madder, and with coal-tar colors. Madder is used for the more common goods, but for the finer, on account of their superior brilliancy, cochineal colors, and for their peculiar hues the coal-tar colors, are used.

The process with madder consists in mordanting the goods with a warm solution of alum and cream of tartar, and afterward immersing them in a madder bath, containing two parts of madder, by weight, to one of the goods, which after dyeing are thoroughly washed. The preparations of madder, such as flowers of madder and garancine, may be used in place of the pulverized root. The dried and ground root, besides containing the two chief coloring principles, alizarine and purpurine, also contains some resinous fawn-colored dyes, which exert an injurious effect when dissolved in the dye; but as they require a higher heat than the two named, it is usual in making a decoction of madder root not to raise it to the boiling point. Flowers of madder and garancine contain scarcely any other coloring matters than alizarine and purpurine. Instead of using the ground root which has undergone a slow fermentation by which the alizarine and purpurine are produced, E. Kopp has invented a process entirely different, and which consists in dissolving the unaltered coloring principle of the living plant, rubian, in sulphurous acid, and subsequently changing it into alizarine and purpurine by the action of sulphuric acid and heat.

The process is extensively employed by MM. Schaff and Lauth of Strasburg. (See Madder.) Woollen may be dyed a scarlet or a crimson by the use of cochineal. In dyeing scarlet, cream of tartar, chloride of tin, and cochineal are used together as a mordant, the dyeing liquor being composed of cochineal and tin salt. If a crimson color is desired, it may be communicated by a single process, or the material may be first dyed scarlet. If by one process, a solution of 2 1/2 oz. of alum and 1 1/2 of cream of tartar for every pound of stuff is used as a mordant, the dyeing being done with an ounce of cochineal and a smaller quantity of tin salt than is used for dyeing scarlet. Scarlet may be turned to crimson by using a bath containing an alkaline solution or alum, the latter being generally used. Wool is usually dyed green by first dyeing it blue, mordanting with cream of tartar and alum, and dyeing again with fustic or weld. Sometimes, as in dyeing the woollen fabric for covering billiard tables, alum, cream of tartar, Saxony blue, and fustic are all put together and the cloth immersed in the mixture and boiled two hours, then thoroughly washed and brightened in a second bath of fustic and Saxony blue.

Woollen goods may be dyed black with aniline black or with a salt of iron and tannic or gallic acid. To obtain the finest and fastest colors, they are first dyed with madder or indigo. The goods are then mordanted with sulphate of iron and put in a bath made of a decoction of logwood, sumach, or galls. The celebrated Sedan black is produced by first dyeing blue with woad, washing, again dyeing with sumach and logwood, boiling three hours, and then adding a solution of sulphate of iron. Wool, by reason of its great affinity for tar colors, may be dyed with them of almost any hue or shade by simple immersion, subsequent exposure to the air, and washing. - Silk, after treatment in the hot soap bath to remove the varnish, may be dyed without bleaching (sulphuring); but when bright colors are required the goods should be bleached. It may be dyed black by means of logwood with an iron mordant; with logwood and bichromate of potash; with gallic or tannic acid in any form, with iron mordant; or, according to a recent method of Jules Per-soz, by mordanting with bichromate of potash and sulphate of copper and immersing in a solution of aniline. Silk may be dyed blue with indigo, Prussian blue, or aniline blue. When indigo is used, it is commonly in the form of sulphindigotic acid, or indigo carmine.

It is dyed with Prussian blue by using a mordant of nitrate of iron. Napoleon blue is produced by using a mordant of nitrate of iron and chloride of tin, passing through a boiling soap solution, and dyeing with a solution of ferrocy-anide of potassium to which has been added hydrochloric acid. The brilliancy is increased by subsequent treatment with solution of ammonia. Silk is dyed with aniline blue by simple immersion for a sufficient time in a solution of the dye in wood spirit or alcohol. Coal-tar colors are now used extensively in dyeing silk, especially the various shades of red, and have largely taken the place of cochineal, although the latter continues to hold its superiority for producing scarlet and crimson. In cochineal dyeing the silk is mordanted with alum, washed, and then immersed in a dye bath made by boiling 2 oz. of white galls for every pound of silk, adding 3 oz. of powdered cochineal, and afterward one fourth of an ounce of cream of tartar, and when it is dissolved, the same quantity of chloride of tin. Silk is more often dyed with fuchsine, coralline, or naphthaline red, the process being the same as for blue, simple immersion and subsequent washing and exposure.

Aniline red, also known as rosaniline, fuchsine, Magenta, and Solferino, is made by combining aniline with various mineral compounds, and also acids, such as chloride of iron, tetrachloride of tin, nitrate of mercury, nitric acid, and arsenic acid, the last named substance being the one most used. The aniline may be separated from its mineral combinations by the action of alkalies, and the precipitate redissolved in acetic or hydrochloric acid, in one case forming an acetate of rosaniline or fuchsine, and in the other a hydrochlorate. Mauve, or aniline purple, was the first discovered of the aniline dyes, and consists of some salt of mauvine, as the sulphate, according to the process of Perkin, the discoverer, which consisted in oxidizing aniline with bichromate of potash and sulphuric acid. It may be prepared by using other reagents, as by the action of chloride of lime on a solution of aniline in hydrochloric acid. Silk is dyed with it by simple immersion in the alcoholic solution until the desired color is obtained. By the addition of acids a more decided purple may be formed.

Since the discovery by Grabe and Liebermann, in 1869, of the process of artificially producing alizarine from anthracene, this dye, which in chemical composition and behavior is identical with alizarine obtained from madder, has to a considerable extent taken its place, and is one of the principal coal-tar colors. It is used with mordants in a similar manner to that for the preparations of madder. (See Alizarine.) Silk is usually dyed yellow, especially on the continent of Europe, with weld, using alum as a mordant. In England, according to the plan of Mr. Bancroft, quercitron bark is frequently substituted, alum being retained as the mordant, to which sometimes a small quantity of tin salt is added. It is cheaper, and is thought to produce a color equal to that given by weld. Silk may be dyed a fast green by mordanting with persulphate of iron, dyeing blue with fer-rocyanide of potassium, and afterward adding the yellow by treatment with fustic; but of late aniline green or emeraldine has been used with as much advantage as it previously had been with cotton. It is produced by dyeing with acid hydrochlorate of aniline goods which have been mordanted with chlorate of potash.

If they are subsequently passed through a solution of ehromate of potash, they are changed to a deep indigo blue, called azurine. - Cotton and linen are more difficult to dye than wool or silk, and require stronger mordants. Cotton may be dyed blue with the cold lime and copperas vat described for dyeing wool, and also by the use of sulphindigotic acid, and linen may be dyed by the same method. Either fabric may be dyed yellow with weld, fustic, quercitron, chrome yellow, or acetate of iron (nankeen). The most brilliant and permanent red which can be imparted to cotton goods, Turkey red, is produced by first saturating them in a mixture of 100 lbs. of Gallipoli oil, 20 lbs. of pearlash, and 50 gallons of water. This mixture is sufficient for the preparation of about 2,000 yards of calico. After padding, the pieces are exposed to the air at a temperature of 90° or 100° F. for 24 hours, and the padding and ageing are repeated as many as eight times when a deep color is required. The portion of the oil which has not suffered oxidation is then removed by steeping in an alkaline solution, and the goods are well washed. To a decoction of 30 lbs. of gall nuts there are added 120 lbs. of alum and 10 lbs. of acetate of lead, and the liquor is made up to 120 gallons.

The goods are then immersed in it and aged three days, and fixed by passing through ground chalk mixture. They are then washed and dyed in madder, to which are added some sumach and blood. For deep colors the galling, aluming, and dyeing are repeated. The color is then a heavy brown red, which is brightened by soaping, or treatment with dilute nitric acid. The influence of the Gallipoli oil (a crude kind of olive oil) has long been a matter of discussion, but no settled conclusion has been reached in regard to it. It has often been attempted to shorten the process, but without success, except in the clearing and brightening, for which garancine, the product obtained by treating madder with concentrated sulphuric acid, has been used with advantage. - The fullest information in regard to the present state of the art of dyeing is given under the various related titles in Watts's " Dictionary of Chemistry" (6 vols., London, 1870-'72), and Wagner's "Chemical Technology" (New York, 1872). Among special works on the subject are those of C. L. and A. B. Berthollet, "Elements of the Art of Dyeing and Bleaching" (London, 1841); Robert McFarlane, "A practical Treatise on Dyeing and Calico Printing" (New York, 1800); M. Reimann, "Handbook of Anilines " (New York, 18G8); Charles O'Neill, " Dictionary of Dyeing and Calico Printing" (Philadelphia, 18G9); and James Napier, F. C. S., "Chemistry applied to Dyeing" (Philadelphia, 1869).