When, in the first half of the nineteenth century, men like Berthelot began to put together organic molecules, they were extending drastically the accepted limits of their science. Instead of confining their investigations to the existing physical environment, they were beginning to imitate the creativity of nature, and it was to be only a matter of time until nature would be surpassed. In a very small way, Berthelot's work with some of his synthetic fats was a start in this direction, but much more remained to be done.
Insufficient understanding of molecular structure hampered the organic chemists of the mid-nineteenth century, but such was the irresistible progress of the science that in at least one significant episode even this shortcoming actually turned out to be an advantage.
At the time (the 1840's) there were few organic chemists of note in Great Britain, and August Wilhelm von Hofmann (1818-1892), who had worked under Liebig, was imported to London from Germany. For an assistant, some years later, Hofmann drew a teen-age assistant, William Henry Perkin (1838-1907). One day, in Perkin's presence, Hofmann speculated aloud on the feasibility of synthesizing quinine, the valuable anti-malarial. Hofmann had done research on chemicals obtained from coal tar (a thick, black liquid obtained by heating coal in the absence of air), and he wondered whether it was possible to synthesize quinine from a coal tar chemical like aniline. The synthesis, if it could be accomplished, would be a great stroke, he said: it would relieve Europe's dependence on the far-off tropics for the supply of quinine.
Perkin, all on fire, went home (where he had a small laboratory of his own) to tackle the job. Had he or Hofmann known more of the structure of the quinine molecule, they would have known the task was impossible to mid-nineteenth century techniques. Fortunately, Perkin was blissfully ignorant of this and, though he failed, he achieved something perhaps greater.
During the Easter vacation in 1856, he had treated aniline with potassium dichromate and was about to discard the resulting mess as just another failure when his eye caught a purplish glint in the material. He added alcohol, which dissolved something out of the mess and turned a beautiful purple.
Perkin suspected he had a dye. He left school and used family money to start a factory. Within six months, he was producing what he called "Aniline Purple". French dyers clamored for the new dye and named the color "mauve". So popular did the color become that this period of history is known as the Mauve Decade. Perkin, having founded the huge synthetic dye industry, could retire, wealthy, at thirty-five.
It was not long after Perkin's original feat that Kekule and his structural formulas supplied organic chemists with a map of the territory, so to speak. Using that map, they could work out logical schemes of reactions, reasonable methods for altering a structural formula bit by bit in order to convert one molecule into another. It became possible to synthesize new organic chemicals not by accident, as in Perkin's triumph, but with deliberation.
Often the reactions worked out received the name of the discoverer. A method for adding two carbon atoms to a molecule, discovered by Perkin, is called the Perkin reaction; a method for breaking an atom ring containing a nitrogen atom, discovered by Perkin's teacher, is the Hofmann degradation.
Hofmann returned to Germany in 1864 and there threw himself into the new work of synthetic organic chemistry his young pupil had opened. He helped to found what, until World War I, remained almost a German monopoly of the field.
Natural dyes were duplicated in the laboratory. In 1867, Baeyer (of the "strain theory") began a program of research that eventually led to the synthesis of indigo. This achievement was, in the long run, to put the large indigo plantations in the Far East out of business. In 1868, a student of Baeyer's, Karl Graebe (1841-1927) synthesized alizarin, another important natural dye.
On such successes as these was founded the art and science of applied chemistry, which in the last few decades has so radically affected our lives and which goes on and on at an accelerating pace. A never-ending succession of new techniques for altering organic molecules has developed, and we must turn aside from the mainstream of chemical theory to examine some of the most important of them. Up to this point our history has lent itself to a straightforward narrative and a clear line of development, but in this and later we shall have to discuss a few individual advances among which very little connection is immediately apparent. Since these advances constitute the applications of chemistry to human needs, they are essential to our short history of the science though they may seen isolated from the main flow.
Naturally occurring compounds of ever-increasing complexity were synthesized after Perkin. The synthetic substance could not compete with the natural product, in any economic sense, except in relatively rare cases, such as that of indigo. However, the synthesis usually served to establish the molecular structure, something that is always of vast theoretical (and sometimes practical) interest.
As examples, the German chemist Richard Willstatter (1872-1942) carefully worked out the structure of chlorophyll, the green, light-absorbing catalyst in plants which makes it possible to utilize the energy of sunlight in the production of carbohydrates from carbon dioxide.
Two German chemists, Heinrich Otto Wieland (1877-1957) and Adolf Windaus (1876-1959), worked out the structure of steroids and related compounds. (Among the steroids are a number of important hormones.) Another German chemist, Otto Wallach (1847-1931), painstakingly elucidated the structure of terpenes, important plant oils (of which menthol is a well-known example), while still another, Hans Fischer (1881-1945), established the structure of heme, the coloring matter of blood.
Vitamins, hormones, alkaloids, all have been probed in the Twentieth century, and their molecular structure in may cases determined. For instance, in the 1930's, the Swiss chemist Paul Karrer (1889-?) worked out the structure of the carotenoids, which are important plant pigments, and to which Vitamin A is closely related.
The English chemist Robert Robinson (1886-1975) tackled the alkaloids systematically. His greatest success was to work out the structure of morphine (except of one dubious atom) in 1925, and the structure of strychnine in 1946. Robinson's work on the latter was confirmed by the American chemist Robert Burns Woodward (1917-1979), who synthesized strychnine in 1954. Woodward began his triumphs in synthesis when he and his American colleague, William von Eggers Doering (1917-?), synthesized quinine in 1944. It was the wild goose chase after this particular compound by Perkin which had had such tremendous results.
Woodward went on to synthesize more complicated organic molecules, including cholesterol (the most common of the steroids) in 1951, and cortisone (a steroid hormone) in the same year. In 1956, he synthesized reserpine, the first of the tranquilizers, and in 1960 he synthesized chlorophyll. In 1962, Woodward synthesized a complex compound related to the well-known antibiotic Achromycin.
Working in another direction, the Russian-American chemist Phoebus Aaron Theodor Levene (1869-1940) had deduced the structure of nucleotides, which served as building blocks for the giant molecules of the nucleic acids. (The nucleic acids are now known to control the chemical working of the body.) His conclusions were completely confirmed by the work of the Scottish chemist, Alexander Robertus Todd (1907-?), who synthesized the various nucleotides, and related compounds as well, in the 1940's and early 1950's.
Some of these substances, notably the alkaloids, had medical uses and, therefore, come under the general heading of drugs. Quite early in the twentieth century, it was shown that complete synthetic products could have such uses, and could prove valuable drugs indeed.
The synthetic substance arsphenamine was used, in 1909, by the German bacteriologist Paul Ehrlich (1854-1915) as a therapeutic agent against syphilis. This application is taken as having founded the study of chemotherapy, the treatment of disease by the use of specific chemicals.
In 1908, a synthetic compound named sulfanilamide had been synthesized and added to the vast number of synthetics which were known but had no particular uses. In 1932, through the researches of the German chemist Gerhard Domagk (1895-1964), it was discovered that sulfanilamide and certain related compounds could be used to fight a variety of infectious diseases. But in this case natural products caught up to that surpassed the synthetics. The first example was penicillin, whose existence was discovered accidentally in 1928 by the Scottish bacteriologist Alexander Fleming (1881-1955). Fleming had left a culture of staphylococcus germs uncovered for some days and then found that it had become moldy. An unexpected circumstance caused him to look more closely. Around every speck of mold spore there showed a clear area where the bacterial culture had dissolved. He investigated matters as far as he could, suspecting the presence of an anti-bacterial drug, but the difficulties of isolating the material defeated him.
The need for drugs to combat infections in World War II resulted in another and more massive attack on the problem. Under the leadership of the Australian-English pathologist Sir Howard Walter Florey, Baron Florey (1898-1968) and the German-English biochemist Ernst Boris Chain (1906-1979), penicillin was isolated and its structure determined. It was the first of the antibiotics ("against life", meaning microscopic life, of course). By 1945, a process of mold culture and concentration was producing half a ton of penicillin per month.
Chemists learned, in 1958, to stop the mold halfway, obtain the central core of the penicillin molecule, and then add to that core various organic groups that would not have occurred naturally. These synthetic analogs had, in some cases, infection-fighting properties superior to that of penicillin itself. Through the 1940's and 1950's, other antibiotics, such as streptomycin and tetracyclines, were isolated from various molds and also brought into use.
The synthesis of complex organics could not be carried through without periodic analyses that would serve to identify the material obtained at various steps in the synthetic process. Usually, the material available for analysis was very small so that analyses were inaccurate at best and impossible at worst.
The Austrian chemist Fritz Pregl (1869-1930) successfully reduced the scale of equipment used in analysis. He obtained an exceedingly accurate balance, designed tiny pieces of glassware, and by 1913 had devised a thoroughgoing technique of microanalysis. Analyses of previously intractable small samples became accurate.
The classic methods of analysis usually involved measuring the volume of a substance consumed in a reaction (volumetric analysis), or the weight of a substance produced by a reaction (gravimetric analysis). As the twentieth century progressed, however, physical methods of analysis, involving light absorption, changes in electrical conductivity, and other even more sophisticated techniques, were introduced.
The organic substances mentioned in the previous section are almost all made up of molecules that exist as single units, not easily broken up by mild chemical treatment, and made up of not more than perhaps fifty atoms. There exist, however, organic substances made up of molecules that are veritable giants, continuing thousands, and even millions, of atoms. Such molecules are never unitary in nature but are always made up of rather small "building blocks".
It is easy to break down these giant molecules to the building blocks and study those. Levene did so in this study of nucleotides. It was natural also to try to study the giant molecules intact, and by the mid-nineteenth century the first steps in this direction had been taken. The Scottish chemist Thomas Graham (1805-1869) was the first, through his interest in diffusion - the manner in which the molecules of two substances, brought into contact, will intermingle. He began by studying the rate of diffusion of gases through tiny holes or fine tubes. By 1831 he was able to show that the rate of diffusion of a gas was inversely proportional to the square root of its molecular weight (Graham's law).
Subsequently Graham passed to the study of the diffusion of dissolved substances. Solutions of substances like salt, sugar, or copper sulfate, he discovered, would find their way through a blocking sheet of parchment (presumably containing submicroscopic holes). On the other hand, dissolved materials such as gum arabic, glue, and gelatin would not. Clearly, the giant molecules of the latter group of substances would not fit through the holes in the parchment.
The materials that could pass through parchment (and happened to be easily obtained in crystalline form) Graham called crystalloids. Those that did not, like glue (in Greek, kolla), he called colloids. The study of giant molecules became an important part of the study of colloid chemistry, which Graham had thus opened up. (In 1833, Graham had studied the various forms of phosphoric acid and showed that in some more than one hydrogen atom could be replaced by a metal. This introduced chemists to the existence of polybasic acids.)
Suppose pure water is on one side of a sheet of parchment and colloidal solution on the other. The water molecules can get into the colloidal chamber, but the colloidal molecules block the passage out. Water therefore moves into the colloidal portion of the system more readily than it moves out, and the imbalance sets up an osmotic pressure.
The German botanist Wilhelm Pfeffer (1845-1920) showed, in 1877, how one could measure this osmotic pressure and from measurements determine the molecular weight of the large molecules in colloidal solution. It was the first reasonably good method for estimating the size of such molecules.
An even better method was devised by a Swedish chemist, Theodor Svedberg (1884-1971). He developed the ultracentrifuge in 1923. This device spun colloidal solutions, forcing the giant molecules outward under huge centrifugal force. From the rate at which the giant molecules moved outward, molecular weight could be determined.
Svedberg's assistant, Arne Wilhelm Kaurin Tiselius (1902-1971), another Swede, devised improved methods, in 1907, for separating giant molecules on the basis of distributions of electric charge over the molecular surface. This technique, electrophoresis, was of particular importance in separating and purifying proteins.
Although physical methods were thus producing evidence concerning the over-all structure of giant molecules, chemists wanted to understand the chemical details of that structure. Their interest centered particularly on the proteins.
While giant molecules such as starch and cellulose of wood are built up of a single building block endlessly repeated, the protein molecule is built up of some twenty different, but closely related, building blocks known as amino acids. It is for this reason that protein molecules are so versatile and offer so satisfactory a basis for the subtlety and variety of life. It also makes the protein molecule that much harder to characterize.
Emil Fishcher, who had earlier determined the detailed structure of the sugar molecules, grew interested in the protein molecule at the turn of the century. He demonstrated that the amine portion of one amino acid was bound to the acid portion of another to form a peptide bond. He proved his case in 1907 by actually linking amino acids together in this fashion (eighteen of them altogether) and showing that the resulting compound possessed certain properties characteristic of proteins.
Determination of the order of the amino acids making up an actual polypeptide chain in a protein molecule as it occurs in nature had to await the passage of another half-century, and the discovery of a new technique.
This technique began with the Russian botanist Mikhail Semenovich Tsvett (1872-1919). He let a solution of a mixture of very similar colored plant pigments trickle down a tube of powdered aluminum oxide. The different substances in the mixture held to the surface of the powder particles with different degrees of strength. As the mixture was washed downward, the individual components separated to form bands of color. Tsvett reported this effect in 1906 and called the technique chromatography ("color-writing").
This obscure Russian paper was ignored at first, but, in the 1920's, Willstatter and a student, the Austrian-German chemist Richard Kuhn (1900-1967), reintroduced the technique. It was refined, in 1944, by the English chemists Archer John Porter Martin (1910-?) and Richard Laurence Millington Synge (1914-1994). They used absorbent filter paper rather than a column of powder. The mixture crept along the filter paper and separated; and this technique is called paper chromatography.
It the late 1940's and early 1950's, a number of proteins were broken down into their constituent amino acids. The amino acid mixtures were then separated and analyzed in detail by paper chromatography. In this way the total number of each amino acid present in the protein molecule was worked out, but not the exact order each held in the polypeptide chain. The English chemist Frederick Sanger (1918-?) tackled insulin, a protein hormone made up of some fifty amino acids distributed among two interconnected polypeptide chains. He broke the molecule into smaller chains, and worked on each separately by paper chromatography. It took eight years of concentrated "jigsaw puzzle" work, but by 1953 the exact order of amino acids in the insulin molecule was worked out. The same methods have been used since 1953 to work out the detailed structure of even larger protein molecules.
The next step was to confirm such work by actually synthesizing a given protein molecule, amino acid by amino acid. In 1954, the American chemist Vincent du Vigneaud (1901-1978) made a beginning by synthesizing oxytocin, a small protein molecule made up of only eight amino acids. More complicated feats were quickly accomplished and chains of dozens of amino acids were synthesized. By 1963 the amino acid chains of insulin itself had been built up in the laboratory.
Nevertheless, even the order of amino acids did not represent, in itself, all the useful knowledge concerning the molecular structure of proteins. When proteins are gently heated, they often lose, permanently, the properties of their natural state; they are denatured. The conditions that bring about denaturation are usually far too gentle to break up the polypeptide chain. The chain must therefore be bound into some definite structure by weak "secondary bonds". These secondary bonds usually involve a hydrogen atom lying between a nitrogen and oxygen atom. Such a hydrogen bond is only one-twentieth as strong as an ordinary valence bond.
In the early 1950's, the American chemist Linus Pauling (1901-1994) suggested that the polypeptide chain was coiled into a helical shape (like a "spiral staircase"), which was held in place by hydrogen bonds. This concept proved particularly useful in connection with the relatively simple fibrous proteins that make up skin and connective tissue.
Even the more intricately structured globular proteins proved to be helical to a certain extent. The Austrian-British chemist Max Ferdinand Perutz (1914-?) and the English chemist John Cowdery Kendrew (1917-?) showed this when they determined the detailed structure of hemoglobin and myoglobin (the oxygen-gathering proteins of blood and muscle). In this analysis they made use of x-ray diffraction, a technique whereby a beam of x-rays passing through crystals is scattered by the atoms of which those crystals are composed. Scattering in a given direction and through a given angle is most effectively brought about when the atoms are arranged in a regular pattern. From the details of the scattering it is possible to work backward to the positions of the atoms within the molecule. For complicated arrangements such as those within sizable protein molecules the task is exceedingly tedious, but by 1960 the last detail of the myoglobin molecule (made up of 12,000 atoms) had fallen into place.
Pauling had suggested also that his helical model might be made to fit the nucleic acids. The new Zealand-British physicist Maurice Hugh Frederick Wilkins (1916-?) had, in the early 1950's, subjected nucleic acids to x-ray diffraction, and this work served to test Pauling's suggestion. The English physicist Francis Harry Compton Crick (1916-?) and the American chemist James Dewey Watson (1928-?) found an additional complication was required to suit the diffraction results. Each nucleic acid molecule had to be a double helix, two chains wound about a common axis. This Watson-Crick model, first advanced in 1953, proved an important breakthrough in the understanding of genetics.
Nor did the giant molecules escape the modifying hand of the chemist. The first case came about through an accidental discovery by the German-Swiss chemist Christian Friedrich Schonbein (1799-1868), who had already made his mark by discovering ozone, a form of oxygen.
In an experiment at his home, in 1845, he spilled a mixture of nitric acid and sulfuric acid and used his wife's cotton apron to mop it up. He hung the apron over the stove to dry, but once dry it went poof! and was gone. He had converted the cellulose of the apron into nitrocellulose. The nitro groups (added from the nitric acid) served as an internal source of oxygen, and when heated the cellulose was completely oxidized, all at once.
Schonbein recognized the possibilities of the compound. Ordinary black gunpowder exploded into thick smoke, blackening the gunners, fouling the cannon and small arms, and obscuring the battlefield. Nitrocellulose was a possible "smokeless powder", and from its potential as a propellant for artillery shells, it received the name guncotton.
Attempts to manufacture guncotton for military use failed at first, because the factories had a tendency to blow up. It was not until 1891 that Dewar and the English chemist Frederick Augustus Abel (1827-1902) managed to compound a safe mixture that included guncotton. Because the mixture could be pressed into long cords, it was called cordite. Thanks to cordite and later "improvements", soldiers of the twentieth century have had a clear view of the battlefield while slaughtering their enemy and while being slaughtered.
One of the components of cordite is nitroglycerine, which had been discovered in 1847 by the Italian chemist Ascanio Sobrero (1812-1888). It was a shattering explosive, also too unstable for war. Its use in peacetime to blast roads through mountains and to move tons of earth for a variety of purposes was very dangerous. Careless use heightened the death rate.
The family of Alfred Bernhard Nobel (1833-1896), a Swedish inventor, manufactured nitroglycerine. When an explosion killed Nobel's brother, he became determined to tame the explosive. In 1866, he found that an absorbent earth called "kieselguhr" could sponge up considerable quantities of nitroglycerine. The dampened kieselguhr could be molded into sticks which were made safe to handle, but retained the power of nitroglycerine itself. This safe explosive Nobel called dynamite. He speculated that it would make war so horrible as to enforce peace. (Yah, right!)
The invention of new and better explosives toward the end of the nineteenth century was chemistry's first important contribution to warfare since the invention of gunpowder, over five centuries earlier, but the development of poison gases in World War I made it quite plain that mankind, in future wars, was going to turn to science for means of destruction. The invention of the airplane and, eventually, nuclear bombs made the lesson even more plain.
There were many other directions in which the peaceful uses of giant molecules predominated. Fully nitrated cellulose was an explosive to be sure, but partially nitrated cellulose (pyroxylin) was safer to handle, and important uses were developed for it.
The American inventor John Wesley Hyatt (1837-1920), in an attempt to win a prize offered for an ivory substitute for billiard balls, began with pyroxylin. He dissolved it in a mixture of alcohol and ether, then added camphor to make it softer and more malleable. By 1869 he had formed what he called celluloid, and won the prize. Celluloid was the first synthetic plastic - a material that can be molded into shape.
But if pyroxylin could be packed into spheres, it could also be pulled into fibers and films. The French chemist Louis Marie Hilaire Bernigaud (Count of Chardonnet) (1839-1924), produced fibers by forcing solutions of pyroxylin through tiny holes. The squirting solvent evaporated almost at once, leaving a thread behind. These threads could be woven into material that had the glossiness of silk. In 1884, Chardonnet patented his rayon (so called since it was so shiny it seemed to give forth rays of light).
Plastic in film form came into its own, thanks to the interest of an American inventor, George Eastman (1854-1932), in photography. He learned to mix his emulsion of silver compounds with gelatin in order to make it dry. This mixture kept and did not have to be prepared on the spot. In 1884, he replaced the glass plate with celluloid film, which made matters so simple that photography, until then the province of the specialist, could become anyone's domain.
Celluloid, while not explosive, was still too easily combustible, and represented a fire hazard. Eastman therefore experimented with less inflammable materials. When acetate groups rather than nitro groups were added to cellulose, the product was still plastic but was no longer dangerously inflammable. In 1924, cellulose acetate film was introduced, at a time when the developing motion picture industry particularly needed something to reduce the fire hazard.
Nor were chemists dependent upon only those giant molecules that already existed in nature. The Belgian-American chemist Leo Hendrik Baekeland (1863-1944) was searching for a shellac substitute. For the purpose, he wanted a solution of some gummy, tarlike substance that resulted from the addition of small molecular units into a giant molecule. The small molecule is a monomer ("one part"), and the final product a polymer ("many parts").
The manner in which monomers join to form giant molecules is not mysterious. To take a simple case, consider two molecules of ethylene (C2H4).
If we imagine a hydrogen atom shifted from one to the other, and one double bond changing to a single bond, so that a new bond can be used to connect the two molecules, we end with a four carbon substance:
Such a four-carbon molecule still has a double bond. It can therefore combine with yet another ethylene molecule, by way of the shift of a hydrogen atom and the opening of its double bond, to form a six-carbon molecule with one double bond. The same process will next lead to an eight-carbon molecule, then to a ten-carbon molecule, etc. (The extent to which this polymerization proceeds depends on the length of time the monomers are allowed to react, the temperature and pressure under which they react, the presence or absence of other substances which may hasten or slow the reaction, and so on. The modern chemist, taking all this into account can design his own final product)
Baekeland began with phenol and formaldehyde as the monomer units and produced a polymer of which he could not find a solvent. It occurred to him that a polymer so hard and solvent-resistant might be useful for those very reasons. It could be molded as it formed and then allowed to set into a hard, water-resistant, solvent-resistant, non-conductor of electricity, which yet could be machined easily. In 1909 he announced the existence of what he called Bakelite, the first and still one of the most useful of the completely synthetic plastics.
Completely synthetic fibers were also to take their place in the world. The leader was the American chemist Wallace Hume Carothers (1896-1937). He, together with a Belgian-American chemist, Julius Arthur Nieuwland (1878-1936), had investigated polymers related to, and having some of the elastic properties of rubber. (Rubber is a natural polymer produced by certain tropical plants. In its natural state, it is too sticky in warm weather, too hard in cold weather to be completely useful. The American inventor Charles Goodyear (1800-1860) discovered, partly by accident, that rubber, heated with sulfur, remained dry and pliant over a wide range of temperatures. He patented his vulcanized rubber in 1944. Rubber truly came into its own in the twentieth century, with the development of the automobile and the need for tires in huge quantities.) The result, in 1932, was Neoprene, one of the "synthetic rubbers" or, as they are now called, elastomers.
Carothers went on to work with other polymers. Allowing the molecules of certain diamines and dicarboxylic acids to polymerize, he produced fibers made up of long molecules that contained atom combinations similar to the peptide links in silk protein. These synthetic fibers, after stretching, are what we now call nylon. It was developed just before Carothers' death, but World War II intervened, and it was not until after the war that nylon came to replace silk in almost all its uses, particularly in hosiery.
At first, synthetic polymers were built up through the processes of trial and error, for little was known about the structure of giant molecules or the details of the required reactions. An early leader in the studies of polymer structure, who removed many of the uncertainties, was the German chemist Hermann Staudinger (1881-1965). Some of the weaknesses of synthetic polymers came to be understood through his work. It was possible for monomers to add to each other in random fashion so that atomic groups on the individual units might point in one direction here in the chain and in another direction there. This randomness would tend to weaken the final product by not allowing the molecular chains to pack together well. Chains might even branch, which would make matters worse.
The German chemist Karl Ziegler (1898-1973) discovered, in 1953, that he could use a resin (a natural plant polymer), to which atoms of aluminum, titanium, or lithium might be attached, as catalysts. These catalysts would bring about a more orderly combination of monomers, and branching was eliminated.
Through similar work by the Italian chemist Giulio Natto (1903-1979), combinations were so ordered that atomic groupings were arranged in orderly fashion down the polymer chain. In short, the art of polymerization reached the point where plastics, films, and fibers could be produced virtually to order, fulfilling properties specified in advance.
One great source of the basic organic substances need to produce the new synthetics in the huge quantities required was petroleum. This fluid had been known since ancient times, but use of it in quantity had to await development of a technique for tapping the vast subterranean pools. Edwin Laurentine Drake (1819-1880), an American inventor, was the first to drill for oil, in 1859. In the century since Drake, petroleum has become the prime ingredient of our society - the principal source of organics, of heat for our homes, and of power for moving objects.
Coal, though we tend to forget it in this age of the internal combustion engine, is an even more common source of organic materials. The Russian chemist Vladimir Nikolaevich Ipatieff (1867-1952), around the turn of the century, began researches into the reactions of the complex hydrocarbons in oil and in coal tar at high temperatures. A German chemist, Friedrich Karl Rudolf Bergius (1884-1949), used Ipatieff's finding to devise, in 1912, practical methods for treating coal and heavy oil with hydrogen in order to make gasoline.
Still, the world's total supply of fossil fuels (coal plus oil) is limited and is irreplaceable.