CORINNE DECELLES Bureau of Standards, Washington, D. C.
EVIDENCE of man's love of color reaches back almost to prehistoric times, yet it is not actually until the modem era that the full range of the rainbow has been accessible to the majority of people in their clothes and other textile surroundings. We are apt to picture ancient or medieval times as being quite splendid with their "Tyrian Purple" and medieval scarlet, but closer examination will show that our present epoch is the first to be literally "bathed in color."
No notable improvements were added to the natural dye sources after the European "discovery" of cochineal, and an estimate of the paucity of available dyes may be made by referring to an Act of Parliament passed in 1552, which limited the number of colored cloths to twenty-one.' MODERN HISTORY
Early Synthetic Period. The great discovery which signaled the end of the old era came in 1856, when William Henry Perkin, a youth of only seventeen, and The history of dyeing may be sharply divided into two great periods, the "pre-aniline," extending to 185% a student of the famous German chemist Hofmann, by and the "post-aniline" period. The former was char- a happy instance of serendipity discovered the acterized by a rather limited range of colors, hut it dye, mauve, while trying to synthesize quinine by the oxidation of crnde aniline. It is interesting to note nevertheless saw the rise of a considerable economic that had he.used pure aniline, which was very difficult system based on the culture of the dye-producing auito he would not have made his dism a l ~and plants. covery. This was not the first synthesis of a dye from The principal vegetable dyes available in the earlier coal-tar period were: madder, a root producing a brilliant red; In 1771 Woulfe obtained a yellow dyestuff from indigo by the indigo; and woad, an inferior blue dye eventually replaced by indigo, ~h~ cultivation of the madder root action of strong nitric acid , . . (picric acid). In 1834 another or spiriholuble dye, aurine, was m& by Rnnge from in both ~~i~ and E~~~~~for ten- yellow was practiced phenol.' tunes, and indigo was grown chiefly in India and the Far East. Other less important vegetable dyes were But Perkin was the fint to realize the industrial possi~ immediately formed a saffron. Brazilwood., auercitron. orseille. and loewood. bilities of such a ~ r o c e s s ,and * the dye. the latter being the only remaining natural dye of any company to This well-publicized discovery stimulated research importance, giving tones from purple to black. Among the most ancient dyes are those of animal into further possible syntheses. Magenta was the next origin. The "lac" dyes, produced from a certain type dye to be synthesized when Perkin's teacher, Hofmann, oi insect, were used in very early times in India, but produced i t from aniline and carbon tetrachloride. During this early period, the English made a serious suffered from the defect of leaving the cloth resinous and gummy. The famous, expensive, and romance- mistake in policy, one which had been paralleled cenentangled "Tyrian Purple" was obtained from the turies before when the government, to protect the growsmall shellfish nurez. We have the ancients' word that e n of woad, forbid the use of the superior dye, indigo. this dye was unbelievably beautiful, but evidence taken Now, instead of aiding the new synthetic dye industry, from ancient samples (it is an extremely fast color) and thereby introducing a new and prolific source of revemodern preparations of i t prove that it ranges through nue to the country, they effectively suppressed it by a rather uninspiring series of reds and purples. After their overstringent and unfavorable patent laws, to the seeing it, we wish that Homer had written about some benefit of their own natural dye products, but also to the great benefit of the incipient German coal-tar inof today's inexpensive coal-tar purples and reds. A far more beautiful natural color was introduced to dustry which advanced by leaps and bounds under the Europe from Mexico in 1518, the brilliant scarlet dye double stimuli of government favor, in the form of loose cochineal, which had been produced on this continent patent laws, and lively research. for some time from the tiny lice which infest certain Up to that time there were very stringent patent laws in Engtypes of cactus. A slightly inferior red had been ob- land and France. The laws of the latter country not only protained from another variety of tree louse by the Per- tected the patents from exploitation by others in that country sians, even in Roman times. This dye, called kermes, was soon supplanted by the superior cochineal. H E ~ N E RJ.,, "Early history of dyeing," J . Soc. Dyers EARLY HISTORY
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*
Written ss a. senior student at T7init.y College, Washington, D. C.
Colowists, p. 3 (1934). ROSE,R E., J. CEEM.EOUC.,3,973 (1926). ROSE,R. E., ibid., 3,975 (1926).
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but in addition protected thenew product from infringement by any type of process. In contrast to this, there was no patent protection for chemical invention in Germany prior to 1876 or in Switzerland prior to 1896. It was due to this unusual advantage, as well as other legal handicaps existing in France and England, that factories were set up in Germany and Switzerland to exploit the discoveries made by English, French, and German chemists in the employ of the Enghsh and French manufacturing concerns.'
cene. Alizarin is the primary coloring matter in madder root, and since its production from anthracene is considerably cheaper than from the natural product, it soon replaced the latter. An indication of the economic significance of this discovery may be gained from the fact that the yearly value of the European madder crop was $17,000,000.6 Within a few years after the discovery by the German chemists, this branch of agriculHowever, England had the initial advantage of greater ture and commerce was totally destroyed. availability of raw materials, so that from the t i e of The next year, 1869, the numerous German chemists Perkin's initial discovery to the year 1869, the great residing in England, undoubtedly feeling the pressure German chemists such as Hofmann and Caro did their of restrictive patent laws, effected a mass exodus to research in England, in close cooperation with the Germany, and with their advent in that country came manufacturers. the phenomenal rise of the German dye industry. The next important event in the industry occurred Even before this date, four of the great German comin 1858, when a brewery chemist, the German, Peter panies had been founded: Hoechster Farhwerken, est. Griess, discovered the diazo reactions, while working 1863; Farbenfabriken vorm, Friedrich Bayer & Co., in his spare time. est. 1863; Badishe Aniline und Soda Fabrik, est. 1865; Fortunately Griess was an astonishingly clever experimenter and Farbwerke Kalle & Co. These young plants got because the compounds he made are among the hardest to handle their needed technical boost when Hofmann and his in the whole realm of organic chemistry. Here was a man who, associates returned from England. Within ten years, for the love of his science and in his spare time, he being a chemist i. e., in 1878, Germany produced seven times as many in a brewery during his working day, developed one of the most dyestuffs as England, eight times as many as Switzerfundamental of all scientific methods! land, and twelve times as many as France. By means of this class of reactions, primary aromatic Germany produced dyes to the value of 50,000,000 to 60,000,amines may be transformed into "diazonium salts," 000 francs, England to the value of 11,000,000francs, Switzerland which although not themselves dyes, may be easily about 7,030,000 francs, and France in the neighborhood of 4,000 "coupled" with a great variety of aromatic amino or 000 to 5,000,000 francs.' hydroxy compounds to produce a great number of The United States had become one of the primary dyeshades. The discovery of this latter fact did not come consumers, but had practically no production of synuntil later, however, when preeminence in the industry thetic dyes. had shifted to Germany. The year 1873 marked the end of a "lull" in French The next year, 1859, Verguin, in France, again pro- research activities when Croissant and Bretonniere disduced magenta, this time from crude aniline and stannic covered that hy heating sawdust with sodium polysulchloride. This gave impetus to the development of the fide, a browndye called Cachou de Lava1 was produced. French branch of the industry, and one more method of Further research on the possibjlity of other "sulfur" synthesis for magenta followed, again in France, this dyes was not resumed for twenty years, when their time by Giraud and de Laire. This discovery was fol- amazing usefulness finally came to light. lowed by the synthesis of the azine dye, thionine, better The next few years saw the introduction of the known as Lauth's Violet after the discoverer. phthalein dyes, e. g., the eosine and erythrosines, disThe following seven years were marked by the covered by the German Caro, who also discovered angradual discoveries of additional dyes, among which other azo dye, chrysoidine. Other German discoveries may be named the Nicholson blues, which were the included methylene blue (1876), the first water-soluble first soluble acid dyes for wool, and especially the brown basic blue color, and malachite green. The latter was and yellow azo dyes. These were formed by the above- the first green of real dyeing value to be used. mentioned "diazo reactions," which had still not The final downfall of the natural dye industry was reached full importance since the dyes they formed heralded by two discoveries made in 1880. The first were rather fugitive and required the use of a mordant of these was the discovery of para red, an azo dye and when used on cotton. the first ingrain dye, that is, one which is formed in the cloth, by &st im&gnating the material with a colorOF THE NATURAL DYE less compound which combines with the fabric and then THE GRADUAL INDUSTRY dipping it into another compound which will react with In the next two years, two events of great importance the fint to form a dye. Para red is a brilliant scarlet to the dye industry in general occurred. In 1868, color, fast to washing (although not to light), and quite Graebe and Liebermann discovered the synthesis of inexpensive. Since the fint two qualities correspond the red dye alizarin from the coal-tar product anthra- roughly to those of cochineal, and since para red is con4 D ~ uT . W., ~ Dept. ~ ~of Cmnmerce ~ ~ , Bulletin, No. 126, 3 (1924). "OSE, R. E., J. CHEM.EDUC., 3.980 (1926).
SACHS, A. P., Textile Colorist,50,245 (1928). of Commmce Bull., No. 126, 4, (1926). 8
' ~ELAHANTP, T.W., Dept.
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siderably l a expensive than the natural dye, the cultiThe synthesis of these indigoid vat dyes and indigo vation of the tiny insects which produce the latter had had the same effect on the indigo-raising business to be abandoned, with the exception of a small amount which the discovery of synthetic alizarin had had on the madder industry. The vast indigo-producing areas used locally in Mexico by the natives. The second discovery is an interesting example of of India began to convert their lands to other crops, intelligent, organized, and directed research. The great and a large commercial activity of the British Empire chemist, Adolph von Baeyer, had been working a t the was sharply curtailed. After these two discoveries, synthesis of indigo since 1865. He and Knop, in 1870, Caro and Kern, in Germany, added another dye to the triphenylmethane group with the synthesis of the beauhad succeeded in preparing it by heating isatin tiful crystal violet, and produced a diphenylmethane H dye, the yellow auramine 0, which also acts as a powerful disinfectant. SYNTHETIC DYES COME OF AGE
with phosphorus pentachloride, acetyl chloride, and phosphorus. They did this after discovering that indigo,
upon oxidation, yields isatin. However, the raw material, isatin, used in the process was costly and rare, and Baeyer found, or rather tracked down, another synthesis in 1880. The new method consisted in heab ing caustic soda and a reducing agent with ortho-nitrophenylpropriolic acid,
In 1884, the wide value of azo dyes was realized when Bottiger discovered the first direct cotton dyecongo red. This was a direct result of Peter Griess's studies on the "diazo reactions" and laid the foundation for the direct cotton dye industry when the affinity of diasotized benzidine derivatives for cotton was discovered. Although congo red itself was not a particularly good dye, being oversensitive to light and acids, it enjoyed great popularity. Other colors with structure similar to congo red were developed, many of them with superior fastness. I n the same year that Congo red was discovered came the synthesis of tartrazine, a yellow lightrfast wool dye, by Zeigler. This dye belongs to the class of dyes known as the pyrazolones. After its discovery, many other pyrazolone dyes were synthesized, and their value as "coupling agents" for direct cotton dyes became known. In 1887, the young English chemist Green obtained a new series called primuline dyes. These were notable because they were diazotized on the fabric from lighter colored undiazotized primuline. Many colon were thus produced by diazotization with different substances, although the primary shade obtained was red, and the new dyes were marked by greater ease of application than para red. The hand of Adolph von Baeyer again appears in the synthesis of rhodamine B. Baeyer, in performing some purely academic experiments on phthalic anhydride and the phenols, had discovered the highly fluorescent fluorescein, of no importance as a dye, but of considerable theoretical importance. As we have seen, Baeyer's co-worker Caro developed eosine and erythrosine dyes from fluorescein, but these dyes, although exceptionally beautiful (they are slightly fluorescent) proved to be quite fugitive, and it was not until 1887 that the substitution of substituted amino phenols for ordinary phenols produced the brilliant red-purple rhodamine B. Many other shades of red and pink may be obtained from this series.
a coal-tar derivative. Indigo produced by this method found some small use in calico printing, but the cost was soon found to be prohibitive, in comparison with the natural product. However, Baeyer had proved the chemical structure of indigo in his research, and thereby made possible the Heumann synthesis in 1890, in which the dye was made by melting phenyl-glycocoll-orthocarboxylic acid with caustic alkalis. Various improvements on this synthesis followed, culminating in the process of Farbwerke Meister, Lucius & Briining, which consisted of melting phenylglycine with caustic soda, caustic potash, sodamide, and water, and oxidizing the mixture with air. This process is the one still in use. In 1936, the United States alone produced over 18,000,000 pounds of synthetic in dig^.^ Baeyer's discovery of the constitution of indigo pointed the way to similar dyes, and by 1905, thioindigo red was discovered by Paul Friedlilnder. Many other of these dyes, all of them "vat" dyes, produced by a slight chemical change of a water-soluble, colorless base which adheres to the fabric, have found wide use. They THE GOLDEN AGE IN GERMANY are especially suited to the dyeing of wool.8 As may be noted, a considerable number of excellent dyes had been discovered in the ten years from 1880 to WERTHEIM, E., "Textbook of 01,ganic chemistry," Phila1890, and this period was for the Germans a golden age, delphia, Blakiston, 1948, p. 703. 0 GREEN, A,, "Fifty yearain the dyeingindustry,"J . Soc. Dyers speaking both figuratively and literally. The Germans may of course be congratulated upon their excellent C h r i s & , p. 49 (1934).
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research work, good business sense, and plant efficiency in those ten years, hut if we examine the facts closely we shall find that their success was not due to their virtues alone. The Germans patented such valuable dyes as the alizarins (red and blues), tartrazine, congo red, rhodamine, henzo purpurin, and diamine red, and sold them to the extensive European market, and to an increasingly important American market a t extremely high prices and for inexcusably high profits. In fact, 30 per cent dividends to stockholders were not uncommon, dividends taken out after a t least onethird of their profits had gone into research and sinking funds for the erection of new plant^!'^ They could easily afford a very large staff of research chemists, proportionately much larger than those of other countries. Statistics bring to light the interesting fact that new discoveries in the dye industry throughout the world are almost exactly proportional to the number of chemists employed. In America, an attempt a t establishing a dye indust,ry was made in 1880, a t Buffalo, and in the following year eight other plants were established. However, the infant industry had to he protected by high tariffs, and was entirely dependent on German dye "intermediates" which could be purchased only a t high prices. In 1883, the high specific tariff was abolished, and the industry collapsed. In France, England, and Switzerland, Germany's only other rivals, lack of government recognition and the necessity of importing intermediates curtailed production to the extent that Germany had a clear field for years. An interesting example of the way in which German fadtories aided their chemists is the story of the two Alsatian chemists R6nB Bohn and Robert Schmidt. When the two friends were both very young, they went to work in German dye factories, Bohn to the Badishe Aniline und Soda Fabrik, and Schmidt to the rival Bayer Factory. Despite their youth, their exceptional abilities were recognized in both factories, and they were supplied with u n l i i t e d aid in the form of assistant chemists and any kind of material or apparatus desired to pursue their rather comical "race" to produce new and better dyes. Bohn started offby synthesizing, for the first time, dyes other than alizarin in the anthraquinone series (to which alizarin belongs) by the use of fuming sulfuric acid. Not to he outdone, Schmidt also went to work on anthraquinone dyes, producing the first acid dyes of the series. Both Bohn's and Schmidt's anthraquinone dyes have proved to he some of the most valuahle dyes in existence, from point of color, fastness, and ease of application, although they are rather expensive. Soon after these early discoveries, the great technical advances in the manufacture of indigo which have been mentioned took place, and Bohn's interest was directed to the possibility of making a comparable compound '0
from an anthracene rather than a benzene base, by approximately the same method used to manufacture indigo. He was highly successful.in this venture, and produced the indanthrene (indigo and anthracene) vat dyes, characterized by a wide variety of beautiful colors and the greatest fastness yet obtained.
THE SULFUR DYES From 1865 to 1893, an amazingly wide range of brilliant and heautiful colors had been developed, many of them exhibiting considerable fastness to light and acids, hut there was still one field which called for improvement, and that was the synthesis of dull, "background" colors with the added quality of cheapness. There were several blacks and browns, and other neutral colors in use, hut they were all either difficult to apply, expensive, or fugitive. In 1893, the field of d i s covery shifted to France, where Vidal, a t the works of Poirrier, decided to go into further research on the twenty-year old reaction which had produced the brown Cachou de Laval, that is, the heating of cellulose materials with sodium sulfide. Vidal soon produced a good, very cheap black, and further research in this field brought out other "sulfur" colors, as they are called, all of which are of dull, or neutral shade, cheap. fast, and easy to apply. Of the single dyes produced in the United States in 1940, sulfur black led the field with the production of 14,633,496 pounds! The chemical history of the sulfur dyes is quite different from that of the other dye classes, since research on this class of substances was preponderantly haphazard and empirical," amounting almost to fusing anything that came to the chemist's mind with sodium sulfide. This is in sharp contrast to the directed, theoretically sound research attending the other dyes, and the situation exists primarily because the chemical constitution of many of the most important sulfur dyes is *till unknown. THE "ICE COLORS"
We have seen that two good red dyes, synthetic alizarin and para red, had destroyed two of the greatest natural dyestuffs in existence. However, the first, alizarin, is rather expensive even in its synthetic form, and since it is a mordant dye, it is rather difficult to apply. Para red, an ingrain dye, is characterized by low molecular weight, and therefore is liable to evaporate off the fiber when subjected to light or heat. It has the added disadvantage that the fimt component in the diazo ingrain dye process, P-naphthol, is not a dye itself and has little real "asffinity" for the material. Green obviated the second difficulty by his discovery of primuline, in which the first component of the ingrain process was a dye, but primuline dyes are even less fast, and more fugitive than para red. The ideal red dye was still forthcoming and the chemists were confronted with somethiig of a dilemma. To increase a dye's reSTONE, I. F., "The Aniline Color, Dyestuff, and Chemical sistance to light, its molecular weight should be in-
Conditions from August 1, 1914 to April 1, 1917," The Carey Prinhg Co., New York, 1917, p. 27.
" ROBE, R. E.,
J. CHEM.EDUC., 3,994 (1926).
NOVEMBER, 1949
creased, but increasing the molecular weight of a red dye ordinarily turnsit blue, with added complex;ty of A Of adding units a t a distance from the color-producing nucleus was finally discovered in 1912 and the extremely vivid naphthol AS red was the product. The method of ingraining for this dye involves diazotization a t low temperatures, and so this dye, and others produced by the same method are called the "ice colors." They range from black to light yellow, and are fast to both washing a n d lieht,. -. n---GERMANY CONTROLS THE INDUSTRY
587
panies, and peripheral enterprises of many types was consumnmated with practised skill. From the date of its renaissance in m 1925-26, I. G. has occupied a status politically and economically which is nearly unique in the modern history of capitalism1"
However, the United States industry had become well founded, and by 1937, our concerns were producing 90 Per cent of our national consumption, an exact reversal of the condition in 1913, when we imported 90 Per cent of our dyes, and made our own few dyes from German intermediates. With the return of I. G. Farben to activitv, however. severe ovemroduction ensued, and the m&ket did noi become stabilized until about 1925.
By the time that the ice colors had been discovered, THE GENERAL POSITION O f THE INDUSTRY the dyeing industry had reached its majority, and had The importance of the dyestuffs industry lies in its at its disposal a wide range of excellent dyes. Germany had full control of the international field, and in 1904, wide usefulness in both peace and war. No mention in order to prevent internal competitive troubles, three has been made of the wide variety of organic products of the largest German concerns formed a cartel. This other than dyes which are produced by the industry, was followed in 1908 by another cartel formed by three but it may be stated that the development of pharmaother large factories. Friction between the two cartels ceuticals almost parallels that of dyes. was kept a t a minimum, and the organizations were so Historically, nearly all of the dye or coal-tar medicines such as successful that in 1916, partly due to war urgency, and aspirin and salvarsan have come directly from the dye industry." partly because of the success of the smaller groups, these six firms and one other independent concern Atabrine and the sulfa drugs are dyes or dye derivaamalgamated to form the world-famous I. G. Farben- tives. The importance of dye intermediates in the manufacture of explosives has been mentioned, and is industrie combiue.12 a fairly well-known fact. Other products which can These important concerns, now eight in number, pooled their be produced from dye intermediates include "perraw-material resources, standardized operations, allocated profits, fumes, artificial flavors, anaesthetics, solvents, lubrietc., without, however, disrupting the autonomy of member concants, motor fuels, inks, lacquers, high explosives, cerns in other respects. plastics, photographic chemicals, tanning materials, INTERNATIONALIZATION Of THE DYE INDUSTRY and other diverse product^."'^ The dyestuffs industry is one primarily dependent on With the outbreak of war, panic swept through the "brain power" and as such it will always provide an dyeing factories in all countries outside Germany with the realization that Germany actually supplied the ever-expanding, fascinating field for those who are world with dyes. Frantic efforts to establish dye in- milling to enter it. dustries began in the United States, and the country REFERENCES broke out with a rash of speakers demanding to know answering BREWIN, A. H., "History of the worshipful company of Dyers, why we had to import so many dyes London," J. Soe. Dyers Colourists, p. 3 (1934). their rhetorical questions mainly by asserting, truthF.B., D ~ of commerce ~ ~ . ~ ~ l N, l ,. ~ 2% ~ (1924). i ~ , fully, that we had no research. The problem was a bit LEGGEIT,W. F.,"Ancient and Medieval Dyes," Chemical Publishing Co., Brooklyn, New York, 1944. deeper than that, but the combination of circumstances occasioned first by the lack of dyes, and secondly by "The Life and Work of Professor William H. Perkin," Chemical Society, London, 1932. the necessity for explosives, many of which are manu- LInLE, A. D,, Situation and Its I,esson,u A, D. factured from dye intermediates, brought about the rise l.ittle Inc., Boston, ~ ~ ~ ~ 1915. ~ h ~ ~ ~ t t s , of the now vigorous American dye industry. MASON,F. A,, "Literature of Chemistry,'' Library of Congress, 1925. After World War I, I. G. Farben realized their now precarious and soon regaining MELDOLA, R., "Jubilee of the Discovery of Mauve and of the Foundation of the Coal Tar Industry," Porkin Memorial siderable power. Committee, h o d o n , 1906. At this time, additional major chemical industries were included, and the integration of raw material sources, power com11 DELDHANTY, T. W., Depl. of Commerce Btzll., No. 126, 5 (1924).
'=WELSH,C. K., "The Development of the Organic Chemical Industry," Thesis: New York Universit.~,1947, p. 14. l4 WELSH,C. K., ibid., p. 9. Is Wni.sn, C. K., ibid., p. 8.
