December, 1926
INDUSTRIAL A N D ENGINEERING CHEMIXTRY
Accurate Physico-Chemical Data
Who among us is brave enough to state the accurate melting point of 0-, m-, and p-nitrotoluenes? Holleman and his associates claim that p-nitrotoluene melts a t 54.4’ C. but a later worker, Vermeuleu, says 51.4’ C. Thousands of dollars change hands each day over these products and who will write accurate specifications? Accurate knowledge of the phase-rule diagrams for these and similar substances allows the accurate forecast of plant results weeks in advance of their actual isolation, so that a rigid control of production is maintained. Yet a recent graduate of a representative university was in complete ignorance of the meaning of a eutectic diagram! This simple illustration may be multiplied by thousands. There is plenty of so-called practical work for the physical chemist. And an executive of a prominent dye concern remarked-not so long ago-that the industry had no place for physical chemists. So I am reminded of the chemist in that concern whose plant batch of dianisidine sulfate suddenly disappeared when too much salt was added to break an emulsion.
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need of this type of work and its fundamental bearing upon our science and this industry in particular. The quantitative aspect of this problem is largely a virgin field. As already mentioned, the absorption spectrum will play an important role. So to physico-chemical methods we must look for most of the new tools. Biological Synthesis
The fact that Nature performs her marvelous syntheses a t practically constant atmospheric pressure and within a range of less than 40’ C. should shake the conceit out of the most stubborn scientist. We need the same devotion to biological synthesis that characterized the period of fifty years following the formulation of the atomic linking theory in the field of organic chemistry. The biological syntheses upon a commercial scale of gallic acid, the higher alcohols, etc., point out the commercial r e ward and the danger threatening the entire organic industry. Plants will be scrapped with increasing frequency in the near future as this viewpoint is grasped by the an-coming hordes of investigators. The responsibility resting upon the present research professor is indeed weighty. Catalytic Synthesis
Accurate Analytical Data
Almost no methods for the qualitatfive analysis of dyes and intermediates are available. It is not a spectacular field in which to work. You cannot publish words enough to satisfy the authorities. Yet few men have contributed more to organic chemistry in the United States than Samuel P. Mulliken with his attempt a t a logical attack upon this complex problem. However, in the Golden Jubilee number of the Journal of the AWTican Chemical Society, no mention is made of this retiring, unsellisah, fruitful investigator other than by name. This fact emphasizes the current lack of appreciation of the tremendous
The brilliant work of Gibbs and his associates upon phthalic anhydride has opened an avenue of scientific and commercial development and justified the entrance of our Federal Government into this field of fundamental and developmental research. Its relation to biological synthesis may be much more intimate than many of us now imagine, for a knowledge of Nature’s catalysts may be the stimulus for the era of biochemical synthesis. One is reminded of the remarks of that brilliant organic chemist, J. U. Neff, who comparing our present method of synthesis in the field of organic chemistry with those of Nature shouted, “We are butchers of molecules-butchers of molecules.”
Relation of the University to the Dye Industry By E. Emmet Reid JOHNS
HOPKXNS UNIVERSITY, BALTIXOR~, MD,
HX relation is one of mutual dependence, a dependence
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more real than appears a t first sight. The modern synthetic dye industry is 100 per cent the product of scientific research. While much of this research, probably the larger part of it, has been carried on in plant laboratories, yet all of it is founded on discoveries made in university laboratories. Furthermore, the men who are responsible for the industrial research are the products of university laboratories and would not be capable of directing research but for their academic training. I n t,he Middle Ages each guild trained its own apprentices, but even the trades have gone past that. The university supplies the foundation on which the industry must build and trains the workmen too. CuriousIy, however, the publicity relations are reversed: the foundation of a building is concealed underground, while here the scientific foundation is on display and the plant research that is built upon it is securely hidden from public view. On the other hand, few foundations are put in for their own sake. In a world where we must earn our keep, few of us can devote any large proportion of our time to matters, however attractive they may be, that do not offer hope of a living. The law is a splendid profession, but how many study it simply as mentaI diversion? Medicine is a fascinating study, but few take it up simply to satisfy their curiosity.
This is‘not saying that professional men are sordid and work only for money. The most of them enjoy the game and play hard for the sake of the game, but there must be some gate receipts else the play cannot continue. All this is a roundabout way of saying that students are not attracted in large numbers to subjects in which there is not the prospect of a career after graduation. There are far more students in chemistry now than there were Bteen years ago, because the chemical industries have expanded in that time and there are more prospective positions for chemists. There are more openings for teachers of chemistry because there is a greater public interest in chemistry. We all think of the enormous development of the organic chemical industry in Germany. Hand in hand with this industrial development went the development of her universities. The one stimulates the other; neither could have grown without the other. Dyes are simply organic compounds and are made by the ordinary methods of organic synthesis. Benzene, toluene, naphthalene, and anthracene are separated and purified by distillation and crystallization. They are then subjected to nitration, sulfonation, reduction, oxidation, chlorination, and diazotization. All of these processes are common to organic chemistry and were discovered in university laboratories before the rise of the dye industry. The great develop
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INbUSTRIAL A N D ENGINEERING CHEMISTRY
ment of the industry followed hard upon the publication of KekulB’s benzene theory in 1865. This has been the Mercator’s chart by which the dye chemists have sailed. Without it they would have gotten nowhere. They would have had to rely upon fortuitous discoveries instead of upon systematic research. It would have taken an unthinkably long time to accumulate enough accidental discoveries such as Perkin’s to provide a basis for the manufacture of the hundreds of dyes that are required. We may particularize a few of the obligations of the industry to the universities. Perkin’s discovery of rosaniline is recognized as the beginning of the synthetic dye industry. Perkin was assistant to A. W.Hofmann, who spent some time on a study of this dye. Its constitution was established by Emil and Otto Fischer in 1878. Malachite green was first made by Otto Fischer. Alizarin was worked out by Graebe and Liebermann. The constitution of indigo was a problem in pure science and engaged some of the best minds for a generation. The theory of color and its relation to constitution is primarily a problem of pure science. Granting that the university and the dye induatry are mutually dependent, the question arises-what can each do to further the interests of the other? There have been many suggestions and what is here offered has little originality, but it is the result of considerable thinking and discussion with others. The University’s Function
It is the function of the university to supply the foundation for technical developments. As it is in the foundation business, the best thing it can do is to lay down better foundations. The broader the foundation the more numerous and important the applications that can be based upon it. The deeper and firmer the foundation the surer will be the structure which it supports. The industry has made good use of XekulB’s theories and of Griess’ diazo reaction. It is in need of new theories, of new reactions, of a better understanding as to how and why reactions take place, and particularly of a deeper insight int:, the cause of color and its relation to constitution. It is the function of the university to seek out these. Industry’s Responsibility
The dye corporations have tremendous research ability a t their disposal-hundreds of thoroughly trained chemists, among them many of the keenest minds to be found anywhere, and splendid laboratories with every modern facility. They have the benefit of much accumulated experience. They can speedily and efficiently take care of the working out of any new ideas that may be brought forward, but they are usually powerless to do fundamental research; they can seldom go on exploring expedit,ions into the unknown. This results partly from the natural division of labor between pure science and applied and partly from the shortsightedness of boards of directors. Millions for applications but not a cent for fundamentals; millions for details but not a cent for principles. The attitude of directors is more or less natural; they are business men charged with making dividends for the stockholders in the quickest and surest way. They are not trustees of endowed research institutions. It is a long, long road a-winding when we start out to discover new principles, but the path from a principle to its applications is comparatively short and certain. Many of the more progressive corporations are changing their attitude towards fundamental research as they are coming to see their need for more basic information. They cannot afford to wait for the universities to get around to their ptoblems. Some of them will be forced into fundamental research, Some of this might well be turned over to the
Vol. 18, No. 12
universities along with funds for its accomplishment. This would be for the benefit of science and of the industry, as the university is the place for pure research. Many attempts have been made to have the universities go over into applied research. The industry rarely goes into the field of pure science and the university should keep out of its applications. The industrialist is sometimes tempted to farm out a problem t o the university, since a subsidy of a few hundred dollars to a teacher is so much less than the cost of research in the plant laboratory with its high overhead. The teacher with his small income is dazzled with the possibility of making a fortune. He loves any research problem but feels somewhat more tenderly toward one that has gold in its mouth. On an industrial problem the teacher is a t a great disadvantage in competition with the industrial organizations. They know the game and have resources far beyond his. When he works out a problem he commonly finds that it has been solved already or that his solution, though interesting, is not practical. It is a temptation to put research students on problems that have technical possibilities, but it is practically impossible to aim a t two things and hit either of them. It is all too easy for the student to get his mind on the money side of a problem, and when he does he seldom does good scientific work. The university has done much for the industry. The industry should do its utmost to aid the university. It helps the university by creating a demand for its students and by increasing the popular interest in science. These help secure support for scientific research. Much assistance can be rendered by supplying materials for investigations. The cost of materials is frequently a serious item to the graduate student, and to the teacher as well. The chief difficulty here is lack of information. Corporations are nearly always glad to furnish even expensive materials in liberal amounts for research, but they have no means of knowing the needs of the university laboratory. The teacher does not know what intermediates are available in the plants and hesitates to ask favors. Benefits of Contact between Industrial Chemist and Teacher
More contact between the universities and the industries would be highly beneficial to both. The situation just mentioned is only one of many that could be improved by a more intimate acquaintance. The industrial chemist gets so absorbed in his immediate problem that he is prone to neglect chemistry as a whole. He finds it hard to keep abreast with scientific progress, particularly in the newer branches. More contact with the universities would benefit him. On the other hand, the teacher is wont to rely upon Beilstein and Richter, which bring chemistry up to January 1, 1910. He gets into certain ways of thinking and tends to keep on in them. He needs contact with the industries to teach him what is going on now. There is much chemistry that is not yet in the textbooks. He needs contact with the keen minds of the industrial chemists. They are wont to ask hard questions and insist on answers. Both sides can benefit by contact. The question is how to secure this. The first thing is for both the teacher and the industrialist to admit that each can learn something from the other. The second thing is to get together. Industrial chemists are persons, although their identity is frequently lost so far as the world outside is concerned. Professors are human, a t least outside of the classroom. When persons get together there is personal contact and that is the real solution of the problem. Personal contact leads to friendship and mutual understanding, and when two men like each other and understand each other they will find a way to help each other. Friends add immensely to the joy of
December, 1926
INDUSTRIAL A N D ENGINEERING CHEMISTRY
Life-in fact, they are responsible for the most of it-but aside from that, friends are extremely useful. American chemists are fortunate in that they have been kept together in one allinclusive society, the meetings of which bring all kinds of chemists together. It is highly desirable that all of us should get out of our own little groups and get acquainted with chemists in other lines. One important function of the Xational Research Council is to be an intermediary between the industridists and the teachers and to serve as a clearing house for information. The future will doubtless show many excellent results from its efforts. In addition to informal contacts, there are often advantages to be gained by teachers working in the plant laboratories during the summer. I n that way they get a real insight into the industrialist's problems and methods. The common objection is that one can accomplish little on a problem in three months. It is a short time, but three nionths is onethird of nine months and the teacher would hate to admit that
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he accomplishes nothing during the nine months session. One who is trained to think should be able to put his mind on a problem and accomplish something definite on it in three months. The amount undertaken should bear a proper relation to the time. il small problem, or one phase of a larger one, can be chosen. A teacher may serve as consultant even during the session, making occasional visits to the plant and keeping in touch .Ir-ith one or two problems. The industry gets the benefit of all the knowledge and experience that the teacher has and pays for only a part of his time. The teacher brings back to his classes much up-to-date information, and nearly every practical problem with which he comes in contact reveals some gap in fundamental knowledge or suggests some purely scientific investigation that is suitable for the university laboratory. To sum up, the university and the industry are mutually dependent and each can profit by better understanding and closer contact, yet each can serve the other best by doing its own work well.
The Development of Synthetic Anthraquinone By K e n n e t h H. Klipstein E. C. KLIPSTEIN&
SONS
Co.,N E W YORK, N. Y.
The A n t h r a c e n e Process
C h e m i s t r y of t h e S y n t h e t i c Process
FFORTS to develop the anthraquinone vat dye industry in the United States presented the vital problem of a source of supply of pure anthraquinone in large quantities and a t an economic cost. Up to the time when manufacturers in this country first attempted to produce the material, only one process had found general application on a n industrial scale. This was the chromic acid oxidation of anthracene. When coal tar is distilled, the fraction known as anthracene oil comes over above 270" C. It consists of anthracene, carbazole, phenanthrene, and other high-boiling constituents. The anthracene contained in the anthracene oil, because of the high percentage of impurities present, is unsatisfwtory as such for the manufacture of anthraquinone, and must be subjected to further purification. This consists of treatment with carbonate of potash, to remove the nonvolatile potassium derivative of carbazole, followed by one or two crystallizations from a solvent such as pyridine. The anthracene is then sublimed to render it in the proper physical form for oxidation. It is next treated with chromic acid until oxidation has been completed. This step is exceedingly simple chemically and can be accomplished with almost quantitative yields, based on the anthracene present. From an economic standpoint, however, a serious problem is encountered in connection with the oxidation in the recovery or disposal of the by-product, chromium sulfate. Although the liquors in some cases have been disposed of without further treatment, and in others have been recovered by regeneration of chromic acid through electrolytic oxid&ion, impurities in the liquors and maintenance of the cells in the electrolytic recovery are sources of unavoidable difficulties. The crude anthraquinone, after separation from the liquors, is dissolved in hot concentrated sulfuric acid to destroy certain of the impurities. The purified product is then precipitated by pouring the sulfuric acid solution into water. The crystals are filtered off and given a final purification by sublimation or crystallization from a suitable solvent.
Despite the apparently definite establishment of the anthracene process to the exclusion of all others, Liebermann, one of the early investigators of anthraquinone and its derivatives, pointed out over fifty years ago that commercialization of a synthetic process might be possible. He stated:'
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Even though anthracene will surely be the raw material in the manufacture of alizarin colors for some time to come, nevertheless technical men should not even a t the present time lose sight of the possibility of the synthetic production of alizarin in other ways. Such a synthesis, for example, would be possible, and it is not a t all inconceivable, if satisfactory yields could be worked out for the methods involving benzyl chloride, benzyl toluene, and o-benzoylbenzoic acid.
It was a relatively simple matter to condense o-benzoylbenzoic acid to anthraquinone with a high yield by treatment with phosphorous pentoxide or, better, sulfuric acid. The key to a commercial synthesis of anthraquinone, therefore, was the preparation of the intermediate o-benzoylbenzoic acid. In 1877 the use of anhydrous aluminum chloride as a catalyst in bringing about reaction between certain types of organic compounds with the elimination of hydrogen chloride was accidentally discovered by Friedel and Crafts as a result of observations made on the action of aluminum metal on amyl chloride. They synthesized first homologs of benzene from benzene and aliphatic chlorides in the presence of anhydrous aluminum chloride, and ketones from benzene and acid chlorides.2 Early the following year they found that acid anhydrides could be substituted for aliphatic and acid chloride^.^ Carbon dioxide, the anhydride of carbonic acid, reacted to give benzoic acid; sulfur dioxide, the anhydride of sulfurous acid, benzene sulfinic acid; acetic anhydride, benzoic acid, and acetic acid as a by-product; and phthalic anhydride, o-benzoylbenzoic acid : CsHiOa
AlC13 + CEHB--+C~~HIUOS
In 1907 Heller showed that in order to obtain a nearly quantitative yield of o-benzoylbenzoic acid a slight excess
* Ber., 7, 805 (1874). 1
Comfit. rend., 84,1392, 1450 (1877); 86, 76 (1877).
a Zbid., 86, 1368 (1878).
