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it would appear to be possible to establish international conventions on economic metal exchanges which might become powerful bulwarks of international comity. The world is not, to our knowledge, growing any metal resources. We have a fixed supply. We cannot as yet pick much from the atmosphere, and the earth’s skin, to a depth of possibly one mile, is about all we can hope to use.
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It is the part of intelligent self-interest to encourage the fundamental sciences, to the end that we may use more of the earth’s crust, to rotate the use of metals as completely as possible through more complete use of secondary metals, and to discourage the use of metals where they are so degraded or disseminated that secondary recovery is impossible.
Synthetic versus Natural Products’ By Roger Adams CWMICALLABORATORY, UNIVERSITY OF ILLINOIS, URBANA, 11.4.
I
N ANY discussion of synthetic versus natural products it is pertinent to look back and weigh the part which natural resources have played in the development of nations. From the scientist’s standpoint historians have recorded little to show that natural resources were appreciated by them as constituting the backbone of an ancient, political state. Historical Background
In reviewing the annals of history, the lives of nationstheir growth from early beginnings through periods of tre-. mendous power to decline and often extinction-have generally been recorded as series of events, political and military. Nothing of interest in the way of natural science is mentioned except as a by-product or a trifling incident. Ancient dynasties are described in elaborate detail, showing how interest was centered in court life, clever and intriguing diplomacy, and the labors of raising military expeditions and fleets. From these facts, which were handed down concerning past centuries, historians have noted various types of influence. In Greece, arts and literature were the things of chief concern. Rome elaborated jurisprudence and the arts of administration. Medieval times were characterized by the growth of ecclesiastical institutions and the Crusades. Colonization, the rise of capital, and the beginnings of experimental science typify the later periods, but not until the nineteenth century do we have the really gigantic strides made by science and its application to industry. Science as being worthy of mention seemingly comes very late in history. It had not gathered together and organized a mass of material sufficient to enable it to be classified as a separate subject, although of course it existed and exercised an ever increasing measure of influence from the very early times. The history of science is a subject of rapidly increasing interest and a closer interrelation of science with history and politics may yet be found. Scientists have perhaps too frequently ignored the historical sources, as historians have often not recognized the significance of science in determining and limiting progress and political independence in the past. PREHISTORIC EPOCHS-Prehistoric periods, such as the Stone age, the Bronze age, and the Iron age, indicate by their very names an early interest in simple chemicals and rather universal elementary scientific training among those early peoples, as these three epochs existed in all quarters of the globe. Buried civilizations give no direct knowledge, but from the existing remains of the past much can be inferred regarding the practical applications of the chemical arts. The smelting of ores, the making of alloys, the tanning of 1 Presented before the Round Table Conference on “The Role of Chemistry in the World’s Future Affairs” at the Sixth Session of the Institute of Politics, Williamstown, Mass., August 11. 1926.
leather, the manufacture of glass and of soap, are all chemical processes. Excavations in the Far East are adding every day to our knowledge and appreciation of the civilization of past dynasties. Jewelry, such as that unearthed in King Tutankhamen’s tomb, shows the skill of ancient artisans in gold and silver in combination with turquoise, gpss, and the semiprecious stones. Unfortunately, the ancient peoples did not hold the manufacturing trades in great respect so history does not chronicle chemical and mechanical inventions in any detail. The reason for this is that such work was left to slaves, while the citizens of Greece and Rome devoted themselves mainly to politics and war. ARISTOTLEGIVES STIMULUSTO RESEARCH-The Outstanding exception of a philosopher turning his attention to experimental science is Aristotle, the teacher of Alexander the Great. He was the first natural historian, and perhaps, all things considered, the greatest, for Charles Darwin once remarked of Linneus and Cuvier that “they were mere schoolboys to old Aristotle.” He anticipated Bacon and the modern scientific movement toward organized knowledge. Furnished the means by Alexander, he had a t one time over one thousand men collecting material for his natural science, and under his immediate successor, though essentially through Aristotle’s impulse, there were some two thousand young men in Athens engaged in cooperative study and research. There was soon, however, an end of this, the first record of endowment for research which was not to be reestablished for two thousand years on any such scale. As Aristotle was ahead of his time, so was Roger Bacon in the thirteenth century ahead of his world, prophesying mechanically propelled ships, horseless carriages, and flying machines. UTILIZATION OF NATURAL REsouRcEs-Natural resources were the treasury of ancient nations. Though details are meager, there are instances where a people’s independence or its supremacy over a neighboring race seems to have been due to a greater supply of certain natural products. These facts are often obscured by the general tendency of the historian to assign a nation’s superiority to the character of its leaders or the “pep” of the people themselves. Themis tocles, whose name in Greek history is associated with thc maintenance of independence against the aggression of Persia, was the genius who created the maritime greatness of the Athenian state. His foresight would not have had the means of execution had it not been that just at this time there began to pour into the treasury large sums of money which had been derived from the public silver mines in the southeastern part of Attica (about 484 B. C.). Through the persuasion of Themistocles the money, instead of being divided up among the citizens, as was commonly done with such surpluses, was devoted to the building of warships, without which the Greeks could not have been victorious over the Persians in the decisive battle of Salamis (480 B. C . ) .
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Another incident, less influential on the course of history but no less typical, is one in the history of Carthage. The First Punic War (241 B. C.) left her exhausted and crushed, paying indemnity and giving up territorial possessions to Rome. Such a disastrous outcome made the Carthaginians determined to repair losses by new conquests in Spain. Hamilcar, a commanding genius, was sent to Spain and spent years in replenishing the coffers of his nation by developing the fabulously rich silver mines in the southeastern part of Spain. It was these natural resources which financed the armies that young Hannibal carried over the Alps against Rome in the Second Punic War, only twenty-two years after a most crushing defeat. This is probably the most remarkable case of national recuperation on record, and it was based mainly upon the vigorous exploitation of known large deposits of metal in a foreign country. Unquestionably, natural resources have played a very significant role in the development of nations of the past, as they do in that of nations of the present. THE ROLEOF SUQAR-AS century followed century, chemical processes became more complicated, and in the life of peoples greater and greater dependence was placed on science as an aid. History repeats itself and nothing better illustrates this than the part sugar has played. When France under Napoleon attempted to dominate the world, England then, as now, was mistress of the sea. With her fleet she could cut off the tropical sugar from her continental neighbor. Napoleon, always desirous to stimulate French manufactures, recalled the early experiment of Marggraf who had extracted sugar from the beet. In 1810 Napoleon offered a prize of a million francs to the one who could develop a practical process of deriving sugar from such a source. A process was found and Germany and France with their beet fields gradually became rivals of the British colonies with their sugar plantations. Ever since the chemist increased the nation’s independence by allowing a nation to grow her own supplies, sugar has been a national issue, being the cause of many conferences and discussions as to bounties and tariffs. The Chemist Recognized
Since about 1860, the chemist’s position has been outstanding. After that time the fundamental laws underlying inorganic chemistry were rapidly extended and applied, and the fundamental laws of organic chemistry were discovered. The principles, upon which were based the industries passed down through centuries, became clear, and with this information the processes were greatly improved. I n the field of organic chemistry more and more new compounds were discovered for which a practical application was found. An intimate knowledge of the chemistry of natural products was gained, and the chemist gradually realized that he was able to synthesize many of these substances hitherto obtained only from plants. Remarkable discoveries followed until it is now only too true that science has progressed faster than civilization. The earlier development came chiefly from university scientists, but with the industries founded on chemistry came the large industrial research laboratories which have more than done their share in contributing not only to the practical application of chemistry but also to our fundamental knowledge. The chemist has gradually replaced many of the metals with alloys, many of the natural products with synthetics, or has found superior substitutes made from his country’s raw material. In all this work he has been stimulated not by the idea of rendering the country independent of others but by the problem of obtaining a better or cheaper product than hitherto available, usually with the idea of commercial development.
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Synthesis of Indigo
An epoch-making accomplishment was the synthesis of indigo. For centuries indigo has been the most important blue dye for fibers and still is one of the blue dyes used in large amounts. Just recently blue ribbons discovered around mummies estimated to be five thousand years old were shown to have been dyed with indigo. Von Baeyer from 1865 to 1880 studied natural indigo from a purely scientific standpoint and then developed a procedure for synthesizing it in the laboratory. It was an accomplishment attained with great difficulties and extensive study, but demonstrated to the chemist and to the world what might be expected from the science of chemistry. Though the original process for synthesizing indigo was not one which would allow the synthetic to compete with the natural product, it was not many years after the first process that one of practical importance was discovered and a keen competition soon existed. In 1897 one million acres in India were devoted to growing the plant from which indigo was obtained. At the present time not more than one or two per cent of the world’s demand for indigo is supplied by the natural product, and large amounts of the synthetic product are exported to India from the United States and Europe. The synthetic product has replaced the natural not only because it could be produced more cheaply and in greater purity but also because it was of more uniform quality and could be more readily made up to a standard strength for the textile manufacturers. With the cutting off of the German synthetic indigo in 1914, the fast declining natural indigo industry was for a time revived and flourished until after the war. During this revival, a prominent British chemist was sent to study conditions and to make recommendations. This chemist, after several years of observation, recently published the statement that in his opinion if the money expended in developing synthetic indigo had been devoted to the development of the natural indigo industry in a scientific way, that is, in the selection of plants, fertilization, cultivation, use of waste, and care in purification and standardization of the indigo for the textile user, the natural product would not only have competed but might even still compete with the synthetic indigo. Whether or not this is true, it in no way detracts from the brilliant scientific and practical development of synthetic indigo or from the stimulation which was thus given to the chemist to seek even greater accomplishments. The Dye Industry
The dye industry in general represents perhaps the field of synthetic chemistry in the highest state of development, a field based exclusively on scientific and extensive study by the chemist. Within ten years from the date of the chance discovery of the first so-called aniline dye by Perkin in England, this investigator had discovered the secret of making aliaarin, that well-known coloring matter of madder root, and within a few years the natural product had been practically eliminated. From that time more and more compounds were discovered, not necessarily the same in chemical character as any natural product, but substitutes which had excellent dyeing qualities. The scientific development of the chemical principles underlying dyes soon made it possible not only to predict what compounds would be dyes but to foretell the colo~and character. The progress then became so rapid that the variety and stability of the synthetic dyes now produced far surpass those found in nature. The natural dye industry has practically disappeared; logwood, a black dye for silk goods, is one of the very few which still remains. The dye industry in the United States a t the present time
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produces about 90 per cent of the total poundage of dyes consumed here, and about 5 per cent of the individual dyes have been discovered and prepared for the f i s t time in America. The erroneous idea that was imbued in the American public for the period of the war and several years thereafter that’American dyes accounted for the inferiority of the colored textiles is now disappearing. The textile manufacturers knew that they were using inferior dyes but did not hesitate to do so because of their relative cheapness. The textile manufacturers a t least now are educated to the fact that in many instances American products are distinctly superior t o those that were ever imported. The stability of many of these synthetic dyes is marvelous. A piece of cotton goods dyed with almost any one of the anthraquinone vat colors can be heated with sodium hypochlorite until the fiber is completely destroyed but the dye will still remain unchanged. This is certainly an endurance test for a dye. It is difficult to believe, as has frequently been said, that the extensive and intensive development of the dye industry in Germany was stimulated by the fact that in case of war the chemical equipment employed would be available for producing war chemicals on short notice. Man is too human to believe that the tremendous profits in the dye industry were not a sufficient stimulant behind the building up of the dye industry in Germany, which in 1914 controlled and produced 75 per cent of the dyes used in the world. To be sure, the government learned during the early stages of development what a tremendous aid to economic power such an industry could be, and as a consequence subsidized it.
might obtain from Norway she had another source of supply for the nitric acid necessary to produce explosives, namely, the fixation of the nitrogen of the air by a process which had just been successfully completed by her chemists. They had developed a commercial method for causing nitrogen and hydrogen to combine to give ammonia and for oxidizing the ammonia to nitric acid. I n 1898 Sir William Crookes pointed out the vast importance to the world of finding a method for obtaining nitrates from the air, since he considered it certain that the supplies of nitrates from Chile in the quantity they were being used a t that time were by no means inexhaustible. This report stimulated a study of different procedures which might be capable of fixing the nitrogen from the air. As a consequence, the Haber process for the production of ammonia from nitrogen and hydrogen combined with the oxidation process of Ostwald for converting this to nitric acid was the reserve which Germany held that other nations did not possess. Within six months after the war started Germany’s Chile saltpeter reserves were exhausted but the synthetic nitric acid was being manufactured in large amounts, thus making possible the continuation of the war. In 1918 Germany was producing sufficient nitrates from the air so that in times of peace she could not only have supplied all her own needs for fertilizer but could have exported an equal quantity in competition with Chile saltpeter. During the past few years rapid strides in several countries have been made in the fixation of nitrogen, and it cannot be long before the large industrial nations will be entirely independent of Chile.
Nitrates
Metals
During the first half of the nineteenth century gunpowder was in its prime as a means of warfare. Potassium nitrate, an essential constituent was not an easy article to obtain. Sodium nitrate was plentiful but on account of its tendency to absorb moisture could not be used in place of’the potassium salt. The exigencies of war stimulated discoveries in former times as they have in the present. The need of more gunpowder in 1852 led to the offering of a prize to the one solving the problem of converting sodium nitrate to potassium nitrate, and a process soon resulted. This discovery led the way to a larger use and scope of gunpowder than in previous periods, particularly since the tremendous Chile saltpeter beds, chiefly sodium nitrate, made this material available in practically unlimited amounts. The first sodium nitrate was exported from Chile in 1830, the industry increasing until a few years ago the exports reached 2 to 3 million tons a year. This prodigious consump tion was due chiefly to its great value as a fertilizer and to its use in producing nitric acid, an essential for the synthesis of a very large number of chemicals of all sorts, including high explosives. The Chile saltpeter beds are so vast, estimated to contain 250 to 300 million tons of saltpeter, that from 1830 until recently this formed practically the world’s source of nitrates. Incidentally, the revenue from the exportation of sodium nitrate from Chile has formed a very large proportion of the revenue of the Chilean government.
Of those chemicals known from earliest times the metals are perhaps of greatest interest. It is easy to see how the primeval savage noticed that when his fires were built on certain kinds of ground the ashes contained metallic substances-for example, he found iron from the reduction of iron ore. After he had observed the properties of this material and attempted to get more of it, it is easy to picture how he gradually bettered his control over the fire. Not content to let it burn by natural draft, he would blow it with his own breath, would expose it to the prevalent wind, would urge it with a fan, or devise valveless bellows. It was not until the fourth century after Christ that the removal of iron from its ores was improved by the use of valved bellows, and then nearly one thousand years passed before any further significant improvement was made. In the fourteenth century, in an attempt to save time and labor by increasing the size and height of the forge and by driving the bellows by waterpower, the length and intimacy of contact between ore and fuel to which the process led, resulted in carbonizing the metal and converting it to cast iron. This is so fusible that it melted and ran together into a single molten mass and freed itself from foreign materials which were impossible to remove by the older process. It was then a simple matter to convert the molten cast iron into useful shapes in spite of its brittleness. Development in the production of iron came more rapidly from this time on, but not until the chemistry of iron was scientifically understood did the modern steel and iron industry appear. The history of other metals has gone through similar stages of development. The ancient peoples were familiar with six metals-gold, silver, copper, iron, tin, and lead. Even in the earliest times the fact that the addition of a little tin, or tin and lead, to copper gave bronze, a more fusible and much harder product than copper alone, was well known. Nor were the ancients backward in seeking other combinations of the metals with which they were acquainted. Long before the Christian Era there were many alloys of copper known which in recent
Nitrogen Fixation
When the Great War broke out, Germany was the largest purchaser of nitrates from Chile, chiefly for agricultural purposes, and in addition undoubtedly had stored a large quantity for making explosives in anticipation of a possible war. As soon as the war threatened she bought all she could in Europe. But with the absolute certainty that the supply from Chile would be cut off by the British, it is unbelievable that Germany would have entered the war had she not been certain that in addition to the small amounts of nitrates she
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times have been unearthed and analyzed. There was a white metal containing chiefly silver with copper, a red metal containing gold and copper, a third consisting of gold, silver, and copper. Alloys
As more and more metals were discovered and came into use, more and more alloys followed. But it has been only for a comparatively short time that the principles underlying alloys have been more satisfactorily understood and the technic of producing them simplified. Now scores of alloys are found on the market each one having its specific use: for example, stainless iron cutlery, which is made of iron containing 12 to 24 per cent chromium; duraluminum, from which many of the German airplanes during the latter part of the war were made. a mixture of 85 per cent aluminum, 5 per cent copper, 5 per cent zinc, and 2 per cent tin; magnalium, an alloy of magnesium and aluminum, as light as aluminum and nearly as strong as steel; Duriron, a product very resistant to acids and also rustproof, an iron which contains silicon in addition to the carbon. These merely represent a very few of those common alloys, among the infinite number possible, possessing the widest variety of properties. During the war the formation of high-speed steels, which may be made by introducing tungsten, manganese, and chromium into steel, was of vital importance to all countries, since these steels are tougher and retain their temper a t high temperatures and can be used for cutting purposes a t white heat. They are used in armor plates, in cylinders of combustion engines, and for castings of all sorts. The Allies controlled the chief supply of tungsten, but the German chemists when confronted with the problem of producing a highspeed steel without tungsten soon demonstrated that molybdenum would give essentially the same results as tungsten. Platinum, which can well be called the king of all metals because of its many desirable properties, is scarce and is found only in a very few districts in the world. Not so many years ago platinum was used extensively for the connecting wires through the glass a t the end of electric light bulbs, particularly because its coefficient of expansion was the same as that of glass. But the chemist discovered that an alloy of iron and 46 per cent of nickel (platinite) would give the same coefficient of expansion and thus platinum no longer has to be used for this purpose. I n spark plugs platinum has been replaced by an alloy of tungsten and molybdenum, and in linings for acid pumps and other such mechanical parts, which must resist corrosion, platinum can well be replaced by illium, an alloy of nickel, chromium, and copper together with small amounts of other metals. This field of alloys offers the chemist an attractive opportunity to help in rendering his nation essentially independent of others in metal resources. All of the six most common metals, with the exception of tin, are found in the United States. One of the largest uses of tin is for the making of tinplate, particularly tin cans, and consists in coating iron with a very thin layer of tin. In the tinning of cans, however, it is practically impossible to get a perfect coating. Since the presence of a pinhole will usually cause chemical action between the contents of the can and the iron, thus producing a discoloration of the foods, :t coating of lacquer must be added. But if a lacquer lining is necessary to make it satisfactory for the contents why should it not be possible to develop a lacquer coating for the iron which would be suitable and thus do away with the tin? This is a timely problem which has not yet been solved but is being studied and when solved will make unnecessary a large proportion of the tin now imported.
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Medicinals
The field of medicinals is perhaps of as much interest to the layman as any in chemistry. Looking back on the develop ment of medicine, many of the most important of our present remedies can be traced to native tribes who learned that chewing the leaves or bark of certain shrubs or trees relieved some particular ailment. It has been, for example, only during the past fifty to sixty years that chemists have learned the art of isolating, in a pure state from the natural source, such important substances as cocaine, morphine, or quinine. But the chemist has gone still further. Not content merely with isolation, he has studied them chemically, and from the knowledge thus obtained has attempted to synthesize them. Of those drugs just mentioned both cocaine and quinine, identical with the natural products, have been prepared in the laboratory. But, unlike indigo and various other natural products, the complexity of the molecule has made an economic process for the synthetic product improbable in the near future. The chemist has realized this, but has not been satisfied to stop here. His chemical study, for example, of cocaine, a drug which since its properties were discovered has been indispensable to the doctor as a local anesthetic, led to the conclusion that only a particular part of that complex molecule was really essential to obtain the anesthesia. As a consequence, he synthesized simple compounds containing groupings of atoms similar to those found to be essential to the medicinal effect of the natural product. His efforts met with success and the well-known substance procaine, perhaps more commonly called novocaine, has replaced a large proportion of the cocaine formerly used. Not only is procaine cheaper but it is also less toxic, and has other qualities of value which cocaine does not possess. Other synthetic products of a similar character have also been discovered. Procaine does not possess the property of mucous membrane anesthesia found in cocaine. Very recently the chemist has turned his attention to this problem and has produced butyn and other synthetics which are superior to cocaine for this purpose, and at the same time do not possess certain of the undesirable properties of cocaine. Oil of wintergreen or methyl salicylate and salicylic acid, both naturally occurring compounds, the medicinal value of which as anti-rheumatics and analgesics was recognized long ago, can now be prepared synthetically for an extremely low price, to the exclusion of the natural product. Moreover derivatives of these substances have come into even greater use; aspirin or acetyl salicylic acid, for example, is now almost a household word in all lands. Perhaps of even greater significance in the medicinal field was the accomplishment of Ehrlich and his students who, starting merely with their knowledge of organic chemistry and the fact that white arsenic was bactericidal to the organism producing syphilis, built up hundreds of organic molecules in which arsenic was combined in different ways, and finally found products which were still bactericidal to the organism but of relatively slight toxicity to the human system. These examples briefly picture the things chemistry has done for medicine in the past. The success already attained can leave no doubt about a most brilliant future. Artificial Silk
Everyone is familiar with artificial silk, or fiber silk-as it is frequently called. It occupies an important place among textiles. Although there is more than one kind, the artificial silks all consist of ordinary cotton modified chemically, thus changing the properties so as to give it the characteristic appearance and luster. Formerly pure cotton had to be used for its production, but now wood pulp is satisfactory. Few realize what an industry this has become. In-the past
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fifteen years the production in the United States has increased from a yearly output of 320,000 pounds to an estimated output in 1926 of approximately 75 million pounds. The natural silk, all of which is imported, was used in the United States to the extent of 50 million pounds in 1922, but this quantity has decreased, little by little, during the past few years, until in 1924 it was only 40 million pounds. Although it is stated that real silk has a place in the industry and there is no danger of its being replaced, can anyone imagine, from the comparative figures given above, that the real silk consumption in the United States would not be growing and would not be much larger than now, were it not for the chemist’s product? Rubber But in some fields progress has been slower. Synthetic rubber is a chemical problem of significance, and one which is of prime interest. With the British control of the raw material, and with the consumption of rubber in this country constituting a large proportion of the world’s total output, the situation in the United States is a perplexing one. The solution lies in the hands of the scientists and a modest expenditure to them, in the hope of getting cheap synthetic rubber from petroleum, would very likely be more economical in the end than expending the hundreds of millions of dollars necessary for developing new rubber plantations in Africa, the Philippines, or elsewhere. The value of manufactured rubber goods in the United States in 1925 amounted to considerably over one billion dollars, and the rubber imported in that year amounted to approximately 430 million pounds. The rubber plantations, which are for the most part in the Far East, cover nearly 7000 square miles of territory and contain several hundred million trees. Tapping the trees for latex, an emulsion containing about one-third its weight of rubber, consists in cutting out a narrow strip of bark with a gouge similar to that used by a carpenter. The strip, about four inches wide, is cut about four feet from the ground diagonally downward about one-third the way around the tree. A groove is channeled at the bottom with the same tool, and the latex oozes from the tree along the channel through a metal spout a t the lower end into a porcelain cup about the siae of a teacup. About an hour after the cut has been made the latex stops flowing. Subsequent tappings are made on alternate days by cutting a thin strip of bark from the surface of the channel thus exposing new surface from which latex flows. The channel is therefore lowered about one inch a month. Nature immediately starts replacing the bark where cuts have been made and by the time the tapping cuts are close to the ground the first cuts are covered with new bark suitable for tapping once more. This cycle of tapping every four years may be continued indefinitely. Trees are still yielding latex after thirty years’ continuous tapping. Contrary to the popular belief, the latex does not flow in a stream from the cut. It drops a t the rate of about two drops per second from a fresh cut, gradually diminishing in an hour to about one drop per minute. The total amount of latex from each tapping is about one fluid ounce, which contains one-third of an ounce of dry rubber. The annual yield per tree is only about three pounds. It requires the output from two full grown trees for a whole year to supply the rubber for one 29 X 4 (Ford size) cord tire. These figures give some idea of the magnitude of the industry and of the importance that the solution of this problem will have upon the American manufactured-rubber industry. Rubber has been made synthebically and the types of raw material necessary are well known. But the serious problem is to find a source of this raw material which is cheap enough to make possible competition of synthetic rubber with the
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natural. Petroleum offers a possibility. When the highboiling petroleum is cracked, in order to obtain low-boiling fractions which can be. used as gasoline in internal combustion engines, there are contained in these low fractions butadiene and its derivatives, the type of compounds which have been shown to be convertible into synthetic rubber. It remains for the scientist to find how the yield of these butadienes may be increased and how they may be economically removed from the other closely related products which accompany them. When this difficult problem is solved, synthetic rubber will not be far off. Suppose that a 5 per cent yield of butadienes might be obtained by a proper cracking and extraction process. On this basis, and assuming that the butadienes might be converted quantitatively into synthetic rubber (a goal which, to be sure, has not yet been reached), it would require the cracking of 52 million barrels of petroleum to provide the necessary butadienes for forming 4 billion pounds of rubber. The total yield of crude oil in the United States in the year 1925 was 758 million barrels and, as a consequence, the volume of 52 million barrels does not appear so large. Moreover, it must be considered that after the 5 per cent of butadienes has been separated the residual petroleum and decomposition products will be available for other purposes and will be decreased in value only by the actual loss in weight of the butadienes removed. ðylAlcohol A discussion of synthetic versus natural products would not be complete without a mention of the process recently developed for obtaining methyl or wood alcohol from water gas or carbon monoxide and hydrogen. Production is not yet thoroughly established, but in a few years the forests formerly used by the wood distillers will no longer be needed. The wood distillation industry, which in this country has a capitalization of nearly 100 million dollars, is certain to be essentially eliminated. Through this process it is possible that methyl alcohol may even become one of our future fuels. This illustrates how a new industry, founded on scientific methods, may supplant an older one where growth has been on a more or less empirical basis. Conclusion The synthetic chemist has invaded every field; he has made synthetic perfumes and synthetic flavors which now rival the natural products; he has replaced lard and tallow by hydrogenated vegetable oils; he has produced synthetic resins which are far superior to the natural. As new situations arise, whether the exigencies of war, the problems of dense populations of rapidly growing cities, the intensive farming demands on soil renewal, the call for new building materials, the demand for specific medicines for treatment of disease, the seeking of new fuel for heat or power, the utilization of waste, the chemist must be called upon. The foregoing examples have been sufficient to show what a start has been made in supplementing natural products by synthetic compounds and substitutes. The chemist will undoubtedly serve the nation even more in the future than he has in the past, not only by rendering natural products more readily available, by utilizing raw materials as yet neglected and waste by-products now discarded, but by increasing the number of cheaper or superior synthetics. The future of synthetic products is assured. There are many problems unsolved awaiting the old and tried as well as the young chemist just entering the profession. A large proportion of the remarkable and successful work in synthetics has occurred in the last twenty-five years. Though the strides made SO recently seem phenomenal, it is safe to predict that the next twenty-five years offer just as great opportunities and will see even more astonishing developments in this field.
