13—
Life and Work in Leipzig
Kolbe's "Merry Celestials"
The phrase in the section head ("hellgeborene heitere Joviskinder") derives from Otto Erdmann and designates in an avuncular and humorous way—but not favorably—the modernist followers of Kekulé in the chemical community.[1] Like Kolbe, Erdmann and many other older chemists were bewildered by the explosion of new ideas and distrusted their power to specify details of molecular architecture. It is a bitter irony that many of the best chemists who passed through Kolbe's lab were (or later became) structural organic chemists: in a semichro-nological list, we can name Griess, Claus, Crum Brown, Volhard, Graebe, Zaitsev, Menshutkin, Markovnikov, Armstrong, Meyer, Ost, Curtius, and Beckmann. Even Edward Frankland, one of Kolbe's oldest and best friends and whom he always considered in some sense a protégé, was distinctly structuralist by the time Kolbe arrived in Leipzig. All of these men had the highest regard for Kolbe, and he reciprocated that feeling. Several of them tried to persuade Kolbe that many structuralist theories were not very different from his ideas and that he ought to pay more attention to them. Some also remonstrated with him about his retention of the older equivalent weights long after nearly all of his colleagues had switched to atomic weights.
A discussion of Kolbe's views on chemical constitution and a comparison with structuralist ideas can be found in chapters 8 and 9. Kolbe's essential peculiarities were his absolute denial of direct
carbon-carbon bonds—the basis of what he called Kekulé's "chain theory"—and his conviction that there was a strict hierarchy of constituent radicals in every compound, with only one being the molecule's "fundamental radical" (Grundradikal or Stammradikal ). We have seen how Kolbe was able during his later Marburg years to more than hold his own in his encounters with the structuralists on a variety of fronts. However, as structural chemistry blossomed and flourished during the late 1860s, Kolbe began to lose pace with the field—as we have already seen in the last chapter as regards aromatic chemistry.
One example of this trend involves the question whether the four valences of carbon might be chemically distinct. Many structuralists, including Butlerov, Erlenmeyer, Crum Brown, and even Kekulé, thought for a few years that this was probable, for there were several cases of apparent isomerisms that could not otherwise be explained. The most notorious such case was the isomerism of "methyl gas" (CH3 -CH3 ) and "ethyl hydride" (CH3 CH2 -H), the first produced by electrolysis and the second by reduction of ethyl compounds, where the two indicated bonds were presumed to engage carbon valences of different chemical value. It was Frankland who discovered and defended this isomerism most vigorously, for the two compounds, although very similar themselves, seemed to result in quite distinct chloro derivatives.
In 1864 Carl Schorlemmer, an expatriate German working at Owens College Manchester, demonstrated the probable identity of methyl gas and ethyl hydride and argued that they formed an identical series of chloro derivatives. Schorlemmer's paper made a great impression, and little was said thereafter by structural chemists about differences between carbon valences. Frankland himself was largely convinced.[2] For two years he had been writing formulas using the reformed weights, and he was then on the verge of adopting Crum Brown's graphical formulas and becoming a structural chemist in the full sense. He wrote to Kolbe, asking him what he thought about Schorlemmer's work.
Kolbe was profoundly un convinced. He would only grant that Schorlemmer had demonstrated that both hydrocarbons yield the same ethyl chloride, still maintaining that "ethyl hydride" is a derivative of methane:
whereas "methyl" consists of two methyl radicals
This was was a departure for Kolbe, for it is the earliest indication that he had finally accepted the dimeric character of hydrocarbon "radicals" (we have seen that he conceded the importance of Wurtz' evidence for this thesis as early as 1855). To maintain his distinction between the hydrocarbons while simultaneously conceding the identity of their chlorinated derivative, he suggested to Frankland that there was a molecular rearrangement of "methyl" to the "ethyl hydride" constitution during the course of the reaction.[3]
To put it simply, from the time he first accepted the tetravalence of carbon (in 1858) to the end of his life, Kolbe assumed that the four radicals around a carbon atom were held with different degrees of affinity. This was also true for other atoms, he thought; the oxygens of sulfuric acid, the hydrogens of ammonia, and so on, were all chemically distinguishable.[4] After Schorlemmer's work, there was little evidence for this idea that most chemists found compelling. Kolbe, however, kept coming back to a single argument again and again; the fact, for instance, that methane can be monochlorinated proved to him that one of the hydrogens of methane is held less tightly than the others. Similarly, the existence of monoderivatives of benzene demonstrated conclusively, he thought, that the six hydrogens are chemically distinguishable, hence Kekulé's theory cannot be right.[5] The empirical failure of the assumption of chemically distinguishable valences, namely, the fact that it predicts numerous isomers none of which were ever found, was excused by Kolbe again and again by one of two gambits: molecular rearrangements or insufficient empirical experience. The structuralists' explanation for monoderivativization, that one hydrogen is randomly selected and the process stops after the first substitution, meant nothing to Kolbe.
These issues were brought to a head for Kolbe in 1866 and 1867 as a result of work on the base-catalyzed self-condensation of ethyl acetate performed independently by Anton Geuther at Jena and by Frankland and Duppa in London. Frankland's work arose out of his successful alkylations of esters using either zinc alkyls or sodium plus alkyl iodides—the final payoff from twelve years of trying to "ascend the homologous series of organic bodies" (see chap. 8). The diethyl substitution product in oxalic ester acquired the name "isoleucic acid,"
Et2 C(OH)CO2 H, because it was an isomer of the hydroxyacid derived from leucine; reduction of the hydroxyl group led to a branched-chain isomer of the straight-chain caproic acid, C5 H11 CO2 H. Substituting one and two ethyl groups into acetic ester yielded butyric and isocaproic acids directly.[6] In a remarkable paper published in 1866, Frank-land and Duppa announced the synthesis by a similar route of acetoacetic ester, as well as of ethyl- and diethylacetoacetic acid, (CH3 CO)Et2 CCO2 H. They found that these compounds decarboxylate in base to produce acetone and ethyl- and diethylacetone, respectively.[7]
It was during the course of this research program (in 1863-1866) that Frankland came over to structural ideas and to Crum Brown's graphical formulas. The details of his intellectual odyssey are not known, but one may presume that he found the modern ideas and formulations simpler and heuristically more valuable than the older ones. Frankland is a good model to compare with Kolbe because both men started from a similar set of views. No one understood Kolbe and his ideas better than Frankland, and no one was better situated than he to help Kolbe to follow along the same path that he had trod. He sent Kolbe an offprint of the culminating paper of this series.
Kolbe studied the paper with care and responded privately at length.[8] That Kolbe had truly invested sincere effort in understanding the paper is evident, not only from the fact that he was able to translate all of Frankland's formulas accurately into his own notational style but also because he suggested a reaction mechanism for acetoacetic ester synthesis that Frankland immediately recognized as superior to his own published conjecture.[9] But it is just as clear that Kolbe failed to understand the structure-theoretical principles upon which Frankland was reasoning. He objected to many of Frankland's condensed formulas because they seemed to posit groups of carbon atoms whose total combining capacity appeared to be short of the number required by tetravalence (for example, a group of two carbon atoms [C = 12] with a valence of six rather than eight, or four carbons with a valence of ten rather than sixteen). The structuralist interpretation of these formulas required subtracting from the sum of all the valences the number necessary to form carbon-carbon bonds, as Kekulé had discussed seven years earlier in the pages of his Lehrbuch der organischen Chemie . Kekulé's treatment was surely the clearest and most influential early exposition of the principles of structure theory, but Kolbe never read it, or at least not until many years had passed.[10]
Kolbe also disagreed with Frankland's formulation of the de-carboxylated compounds as derivatives of acetone. Rather, Kolbe averred, they were derivatives of methane, for example,
One could conceive of an ethylated or diethylated acetone, but that is a different compound, he argued, because it is derived from a different fundamental radical (Stammradikal ). Kolbe's systematic and elementary way of attempting gently to disabuse Frankland of his putative errors indicates that Kolbe had simply failed to follow Frankland's and Duppa's structure-theoretical exposition. He was also strongly opposed to the use of graphical formulas:
Frankly, I believe that all of these graphic representations are inappropriate for the times and are even dangerous, because they leave too much scope for the imagination, as for example happened with Kekulé: his imagination bolted with his understanding long ago. It is impossible, and will ever remain so, to arrive at a notion of the spatial arrangement of atoms. We must therefore also take care to avoid drawing a picture [of that putative arrangement] for ourselves, just as the Bible warns us from making a visual depiction of the Godhead.[11]
Kolbe laid all this out (without the metaphors) in a publication a year later. He wrote, "I expect to hear the objection which is repeatedly made to me orally," that his formulas are identical with Frankland's and Duppa's. "To be sure, they may appear so on superficial examination," but he and Frankland had chosen different fundamental radicals, and so it was clear that they were referring to isomeric and not identical compounds—just like, for example, ethyl acetate versus methyl propionate.[12] For Kolbe, choice of the base radical appears to have been crucial because of the presumed differences in carbon valences, but he did not make this assumption explicit.
Kolbe's friends and old students commiserated with each other. Frankland wrote to Crum Brown about this correspondence: "I am just now endeavoring to get Kolbe to express certain of his fundamental formulae graphically. We should then understand each other better." Crum Brown replied,
I quite agree with what you say of Kolbe. I worked with him for a summer session at Marburg. I was always able to explain any theoretical views of mine to him by first translating them (sometimes with a good deal of trouble) into his language, but I am quite sure he would fail to recognize his own ideas if translated into our language. For instance as to his HO . . . [C2 O2 ]O he certainly regards the HO as water, but he recog-
nizes the fact that there must be as many HO's at the beginning of the formula as there are O's outside the bracket at the end of it, & he points out (for the first time I believe) that [C2 O2 ] or CO is a group capable of combining with two equivalents & that in acetic acid it is combined with one equivalent (or atom) of C2 H3 methyl & one equivalent (or as we shd say 1/2 atom) of oxygen. To this he adds HO & as far as I can see the only difference between his view & ours is that he does not explain why. We say it is because the 1/2 atom of Oxygen in the HO is the other half of that which is combined with the CO. His obstinate opposition to O = 16 prevents his accepting such an explanation.[13]
Kolbe's article forced Frankland and Duppa to respond publicly. They praised Kolbe's proposed mechanism, agreeing that it was more probable than their suggestion, but they fulfilled Kolbe's prediction by arguing in great detail how the formulas they employed for the new compounds, both condensed and graphical, were entirely equivalent to his, providing that "Kolbe does not invest in his symbols some meaning that we cannot understand." They noted that the dividing up of a constitutional formula into radicals was a purely arbitrary operation, a matter of expository convenience and not ontology. Consequently, they were uncertain of the exact significance that Kolbe attached to his apparently important word Stammradikal . But even if there were a real difference in the compounds due to a difference in the "fundamental radical," they argued, this is certainly not analogous to the ethyl acetate versus methyl propionate case: the latter compounds have differences in the bonding order of the atoms in the molecule, whereas the Frankland-Duppa and the Kolbe formulas indicate the same atoms combined in apparently the same way.[14]
Not only Crum Brown, but also Graebe, Volhard, and other senior workers who passed through Kolbe's Marburg laboratory had to do the same sort of routine formula translations as Frankland did in order to converse (and argue) with the master. Referring to the same summer semester as Crum Brown had (1862), Graebe later wrote,
The radical theory as he developed it was at that time an excellent point of departure from which to understand structure theory, which was just then developing. It was only necessary to rewrite his formulas (at that time still being written in equivalents) into the new atomic weights, in order easily to understand the structural formulas.[15]
Volhard, too, did this sort of routine formula translation and became the first from Kolbe's lab actually to publish in atomic weights.[16] The same was true, of course, in Leipzig. Armstrong arrived there from Frankland's laboratory in 1867, and several Butlerov students passed
in and out during the early Leipzig years, especially A. M. Zaitsev and V. V. Markovnikov; all had absorbed structural ideas from their first mentors. Kolbe stated repeatedly, and all evidence from his students substantiates the claim, that he encouraged his students to follow their own ideas, to disagree and argue with him. A surprising number of publications by his students in Leipzig contain views with which he was known to disagree. At times this went so far that Kolbe attached long footnotes to student papers outlining his disagreement with them.[17]
Markovnikov's memoirs contain the most revealing anecdotes along these lines. Soon after his arrival in Leipzig in the fall of 1866, he wrote Butlerov (for whom he had served as assistant and lecturer in Kazan) that Kolbe was far from a martinet, that he positively enjoyed arguing with students, and that he (Markovnikov) had already succeeded in locking horns with him more than once. Moreover, Kolbe actually used Markovnikov to help him interpret modern formulas.[18] As it happened, Markovnikov's research project was related to the Frankland-Duppa material, for Markovnikov was attempting to show that Frankland and Duppa's product from the dimethylation of oxalic ester was identical to Staedeler's "acetonic acid" and that both had the structure of what could be more rationally named hydroxyisobutyric acid. This project was successful.[19]
Markovnikov related many years later that as he was writing up these results and preparing to leave Leipzig for Kazan (this must have been in the summer or early fall of 1867), he had one more tussle with his mentor. Kolbe had claimed that one of his formulas was wrong, but Markovnikov was emboldened by one of Kolbe's assistants who privately sided with him. He was invited into Kolbe's private office to discuss the matter.
The heart of the dispute was the old oxygen theory. "You don't understand me because you are not used to my formulas," said Kolbe; "I will express your thoughts in your own formulas." "Aha," I thought, "now, Herr Professor, you are mine." . . . He began to write, stopped halfway through the formula, thought a minute, then set the pencil down. "Ja, Sie haben Recht." Then he completed the formula and said once more, "Yes, yes, this is true; you are right," and somewhat confusedly began to explain something. I quickly retired, to spare the self-esteem of an honored teacher. A year later, I received from him a pamphlet on another of our disputed questions. In it he developed his theoretical ideas in detail, but now he wrote the weight of oxygen in the new way.[20]
It would be nice to know more details. What was the disputed point, and what was the formula? There is no particular warrant for the accuracy of this story, but the timing seems to fit. It was a little more
than a year after Markovnikov's departure that Kolbe sent colleagues offprints of his dissertation on hydrocarbons, which was the first time he published in the new atomic weights. On the other hand, Markovnikov was only one of several who were putting pressure on Kolbe at the time; Frankland's article in rebuttal to Kolbe's public response may have had more influence on him, at least regarding the atomic weight issue if not the more general formula question.[21]
The actual point of conversion for Kolbe from the older to the newer weights appears to have been the summer of 1868, just when Carl Graebe was beginning to pass the various stages in the habilitation procedure. Graebe had studied with Kolbe for a semester in Marburg, but had been most strongly influenced by the structuralist school, especially by Baeyer; his Habilitationsschrift was entirely based on the Kekulé benzene theory. The phrase "hellgeborene heitere Joviskinder " (quoted at the beginning of this chapter) was directed sarcastically to Graebe, but its author (Erdmann) and Kolbe both enthusiastically approved the habilitation. The fact that Graebe chose Kolbe's lab for habilitation, certainly with full knowledge of Kolbe's contrary theories, indicates once more that Kolbe was trusted implicitly (by those who knew him) to respect opposing points of view.[22]
In the event, Graebe was Privatdozent in Leipzig for only one semester, winter 1869/70. One of his auditors was Kolbe's student Ernst von Meyer, who was then in his fourth semester of study. In his memoirs, Meyer stated that he derived great profit from Graebe's instruction, absorbing and learning to appreciate the new structural chemistry. From then on, he added, he could read with full understanding articles in both the older and the newer styles and had no difficulty in translating one into the other. Although he agreed with Kolbe's criticism of the sloppy and conjectural character of much modern chemistry, Meyer respected and valued structure theory, a point that he stressed in correspondence and that emerges clearly from his historical writing.[23]
The Leipzig Research Group
As we did for the Marburg period, let us begin our analysis with some numerical measures of research productivity using the standard unit of productivity, the published paper. This time we take data across Kolbe's entire career, as shown in table 3.[24]
Some patterns are apparent in this table. In the early Marburg period—before acquisition of the "carbonic acid theory"—Kolbe's research productivity was low, as was that of his students. The high point of Kolbe's career came during the 1860s, when he was publishing
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around three good papers per year and his group authored about ten per year. This overall level of productivity roughly doubled after the great surge in enrollment in the early 1870s, so that he began to publish half a dozen or more solo papers per year and his group about twenty per year. However, this late period was not as productive as it might first appear. For one thing, he had far more students with which to work—five to ten times as many as in Marburg—so that in this light a doubling of total yield appears modest. Moreover, the great majority of his own publications after 1875 were either short notes with no experimental results or polemical critiques.
How does this overall productivity compare to his contemporaries and near contemporaries? His numbers were modest compared to those of Liebig or Wöhler a half generation earlier, to Hofmann in his generation, or to Baeyer a half generation later, each of whom had several hundred personal and collaborative papers; Baeyer's research group at Munich alone is said to have published over 1600 papers.[25] However, Kekulé himself, certainly the most theoretically important chemist during the third quarter of the century, published only 131 papers, all but 18 of these during the years 1850-1873.[26] As has often been rightly remarked, numbers of publications do not necessarily correlate to quality or significance.
So let us now attempt to characterize the Leipzig school in terms of subject matter and its significance. Two areas that we have already explored are the synthesis of natural products (chap. 10) and experimental investigations connected with theoretical issues involving romatic compounds (chap. 12), both of which were also represented in Marburg. Another continuation from the Marburg period
was the prediction and production of novel aliphatic isomers, especially secondary and tertiary alcohols and acids. One important field largely new to Leipzig and forming the topic of dozens of his students' dissertation projects was organosulfur compounds. Included in this group were studies on aliphatic and aromatic sulfides, sulfates, sulfonic acids and esters, sulfinic acids and esters, and other organic sulfonyl and sulfoxyl compounds. In the process, scores of new substances were discovered, including the first members of entirely new classes of compounds, such as the dialkyl sulfones, dialkyl sulfoxides, and nitroalkyls. One of the leading ideas motivating this research was Kolbe's conviction, contrary to Kekulé, that the valence of an element was not constant but rather could vary. Indeed, the novel organosulfur compounds named include substances containing divalent, tetravalent, and hexavalent sulfur. The last field that deserves mention is a long series of investigations after 1873 on the preservative and antiseptic properties of salicylic acid, as discussed in the preceding chapter.
In terms of quality and significance, nearly all of this large body of research was quite competent and most of it was scientifically important. However, little of the work done after around 1870 opened up new theoretically significant opportunities. The most exciting topics elsewhere in Germany—positional isomerism in the aromatic field, synthetic methods, structure determinations, and after 1876, stereochemistry—were all outgrowths of the classical structure theory that Kolbe so abhorred. Simply stated, in the 1840s and 1850s, Kolbe had been a principal founder of the investigation of "constitutions" of organic compounds; in the 1860s, he was well able to keep pace with the leaders of the field and to make substantial contributions; but after 1870, the contemporary significance of his work declined dramatically.
Besides research, the other significant activity of an academic institute is education, and so we must now turn to Kolbe's students and junior colleagues in Leipzig. Unfortunately, class lists have not survived, and so a complete analysis by name or even by precise statistics is not possible. From unsystematic indications of the course of overall enrollments, we can presume that Kolbe must have taught something like 1500-2000 Praktikum students during his nineteen years in Leipzig. Many of these were not chemistry majors and had no further contact with the science after their one brief exposure; even some of the chemistry and pharmacy majors doubtless had virtually no impact on the institute. How many people, then, can be considered members of Kolbe's "school"? The widest definition would include all of the following groups: (1) all who published at least one paper from the lab, regardless if they took a degree; (2) all who received a Ph.D. under Kolbe (for which records do exist), regardless if they published; (3) all
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assistants, Privatdozenten, and postdoctoral guests, regardless if they published; and (4) all who were mentioned as having assisted in any of the 369 papers in table 3 that date from the Leipzig years. The Leipzig research group in this widest sense consists of 137 identifiable people, just half of whom (68) completed Ph.D. dissertations under Kolbe and all but a dozen of whom appeared as paper authors. These numbers suggest that an average of something like 30 of them were present at any given time, so that his group of advanced Praktikanten may have averaged around 40. Collating these numbers with those from Marburg gives the summary shown in table 4.
Whereas Kolbe's Marburg group was, until his last few years there, almost exclusively composed of Kurhessian students, the group in Leipzig was far more cosmopolitan. About one-fourth of the group was foreign, and of the Germans only about one-third came from Saxony. In his entire career, Kolbe could boast of having taught twenty-one Russian students, twenty Brits, ten Americans, seven Swiss, three Austrians, and a smattering from five other countries (but no French, Italian, or Spanish students). Of these, five Russian and seven British students took their Ph.D. degrees with Kolbe.[27]
Indeed, it was with his foreign students that Kolbe had many of his greatest educational successes. Edward Frankland (as sort of an unofficial Kolbean) and Henry Armstrong (1848-1937) were two of the most influential science educators of their day in England, and they were considered the deans of late nineteenth- and early twentieth-century British chemistry, respectively. Zaitsev (1841-1910), Menshutkin (1842-1907), and Markovnikov (1838-1904), all world-class chemists, made a great impact in Kazan, St. Petersburg, and Moscow during and after the life of their teacher Butlerov. After receiving his Leipzig Ph.D., the Russian Constantin Fahlberg (1850-1910) bounced around several positions before spending a year as an assistant to Ira Remsen at Johns Hopkins University in Baltimore, where he (systematically)
discovered saccharin and (serendipitously) its sweetening properties. In 1886, he founded a factory near Magdeburg to manufacture the substance, with great success and profit.
As for Americans, we have noted that future Harvard president Charles Eliot (1834-1926) spent a semester with Kolbe in Marburg. H. P. Armsby (1853-1921), who became a noted agricultural chemist at the University of Wisconsin and at Pennsylvania State College, was a Leipzig Praktikant in 1875-1876, as was the New York private analyst Gideon Moore (1842-1895). One last American Praktikant worth mentioning is Sidney A. Norton (1835-1918), who for twenty years was head (and only member) of the chemistry department of Ohio State University.[28] Perhaps the most curious foreign career path was traveled by the Bavarian Oscar Loew (1844-1941), who had stints at the City College of New York, the United States Geological Survey, the Department of Agriculture, and Tokyo University before returning to his homeland at the age of seventy as honorary professor at Berlin. He was the last significant Kolbe student to die.
The highest prestige that a German professor could wish for a student was that he become an ordentlicher professor himself at another German university. Here Kolbe had little success. Only three of his students ever gained a university Ordinarius: Ernst Beckmann (1853-1923) at Erlangen, Leipzig, and Berlin; Theodor Curtius (1857-1928) at Kiel, Bonn, and Heidelberg; and Ernst Schmidt (1845-1921) at Marburg. Schmidt, the only undistinguished chemist of the three, became the first to achieve this rank—ironically, at Kolbe's former university and in the very year of Kolbe's death (this was as Zwenger's successor as director of the pharmaceutical institute).[29] This poor record of spawning new full professors contrasts with that of Liebig a half generation earlier, and with Baeyer a half generation later, each of whom taught close to thirty future German university Ordinarien.[30]
This last enumeration counts only those who actually received a Ph.D. under Kolbe, not his entire research group. Moreover, there were other educational institutions besides universities, other ranks besides the Ordinarius, and other countries besides Germany. Of the total group of 137 students, 31 (twenty-three percent) pursued academic careers. Among the non-Ph.D. students in Leipzig were such future academics as Carl Graebe, Edmund Drechsel, Hermann Credner, and Gustav Hüfner, as well as many of the foreigners mentioned earlier. Among those who never made it to Ordinarius but nevertheless built reputations in chemistry were Conrad Laar (1853-1929), who coined the term tautomerism ; Rudolf Leuckart (1854-1889), who developed an eponymous synthetic reaction that yields complex aliphatic amines; and Friedrich Fittica (1850-1912) at Marburg.
The last group of academics comprises those who worked at the trade schools and technische Hochschulen, which were gradually raising their status during the latter part of the century. Kolbe's Marburg student Rudolf Schmitt had an excellent career at the Dresden Polytechnic, and when ill health forced him to retire, his successor was Ernst von Meyer (1847-1916). Hermann Ost (1852-1931) was at the Hanover Technische Hochschule for nearly forty years, and in all, about a dozen of the 137 Leipzig Kolbeans spent major portions of their careers at technical schools.
It has been noted that only twenty-three percent of Kolbe's Leipzig group—or to put the matter more starkly, only two percent of his Praktikanten—had a subsequent academic career of any sort. The majority of Kolbe's Praktikanten were instead future physicians, pharmacists, schoolteachers, businessmen, civil servants, and so on, no doubt even including a few law and theology students.[31] The future academics were in the minority even among the future professional chemists, for in the last third of the century, a university education was becoming common, even expected, preparation for a career in the chemical industry. Unfortunately, biographical sources for industrial employees are poor in comparison to reference works for academics, and so it is difficult to identify Kolbe's budding industrialists even from an accurate list of names.
However, some identifications, at least, are clear. Kolbe's Marburg student Wilhelm Kalle founded what would become an extremely successful dye firm two years after obtaining his Ph.D., in 1863. Ludwig Mond, the later ammonia-soda magnate, also studied in Marburg. Griess, Graebe, and Gerland were all Marburg students who worked in the chemical industry. In Leipzig, there was a larger (and increasing) percentage of technical students. The case of Fahlberg has already been mentioned, but this example is only representative. Some two dozen of the Leipzig students can be shown to have entered industry, but the true number is certainly very much higher. A rough estimation can be made that perhaps twenty-five percent (around 400) of his Leipzig Praktikanten became industrial chemists, contrasting with perhaps nine percent (about 20-25) of his Marburg students.[32]
Meyer, Ost, and other junior colleagues contributed far more to the liveliness and success of Kolbe's institute than has been appreciated. Both Meyer and Ost were assistants and Privatdozenten in the institute from the early 1870s until Kolbe's death in 1884, Meyer being promoted to Extraordinarius in 1878. They had capable colleagues in fellow long-term assistants Anton Weddige (1843-ca. 1904) and Ernst Carstanjen (1836-1884), both of whom also became ausserordentlicher
professors at Leipzig, but neither of whom progressed further along the academic ladder.
Although all doctoral degrees in chemistry were officially granted with the Kolbe imprimatur, it appears that Ost and especially Meyer began increasingly to take over day-to-day direction of the Doktoranden, especially after Meyer's promotion to Extraordinarius. Judging by acknowledgments in doctoral dissertations and by Meyer's later statements, it seems that the majority of the doctoral students after 1877 got most of their advice, and even many of their original topics, from the junior members of the institute. Meyer mentioned that his Ph.D. topic, selected in 1871, was of his own devising. However, the trend was certainly stronger after the mid-1870s, a period that corresponds to a serious decline in Kolbe's health. The fact that the two most eminent Kolbe students, Ernst Beckmann and Theodor Curtius, were in this late group, speaks to the quality of Meyer's mentoring.[33]
During the first Leipzig decade, of course, Kolbe's role was stronger and more direct. There are many indications (from Kolbe's acknowledgments of specific students' assistance in some of his papers, from students' acknowledgments to Kolbe in their papers, and from retrospective accounts) that Kolbe often used his students as his "hands" to pursue his own concerns; examples include much of the organosulfur research and his search for aromatic isomers. Indeed, Kolbe's Leipzig period might be viewed as exhibiting all the prerequisties for an ideal research school. Taking Jack Morrell's well-known criteria for such an entity,[34] we can affirm that Kolbe was a man of eminence and personal charm if not charisma; that his students formed a cohesive group with excellent esprit; that they were allowed to publish under their own names, and after 1870, in Kolbe's own proprietary journal; that Kolbe had a distinctive theoretical research program to be elaborated, with a set of dependable and predictable techniques; and finally, that he had plenty of manpower, more than adequate physical facilities, and generous institutional and financial support. Why, then, was the Leipzig school not more successful than it was?
In the course of a compelling endorsement of research schools as a unit of historical analysis, Gerald Geison notes some inherent difficulties with this kind of approach, to which additional ones may be added.[35] For instance, it is by no means clear that research groups are always the cohesive and distinctive units they are sometimes assumed to be. Indications of transmission of ideas from teacher to student may be inferred, but dependable statistical data can rarely if ever be constructed. Exactly which themes were suggested by Kolbe, which by his assistants, and which by the students themselves? A formal ac-
knowledgment by a student to the group leader does not really tell us very much. Even for those cases where we can determine that the project started as a definite assignment, scientific research is such that few projects lead in a straight line from conception to conclusion, and the twists and turns along the way are often the real points of interest; who was doing the twisting at each point?
If such are typical of the historian's analytical problems for the Doktoranden, the difficulties are even worse for guest Ph.D. workers, assistants, Privatdozenten, and other junior colleagues. The German university system was fluid; junior colleagues frequently traveled from university to university, and many had not been Kolbe's students originally. Nor was it just the junior colleagues, for the Doktoranden themselves were also often a peripatetic lot. Moreover, organic chemistry, at least, had developed a national scientific culture that was highly similar at the various German universities. Enough has been said in this chapter (and in chaps. 5, 11, and 12) to demonstrate that structural chemistry was alive and well in Kolbe's institute, even while Kolbe was turning apoplectic over it. Themes of students' projects were frquently irrelevant (or even contrary) to Kolbe's pet concerns, and this is true even in the early Leipzig period. As extreme cases of independence, some notable disagreements between Kolbe and his students were published under the auspices of the Leipzig lab.[36]
Kolbe's group research was notably moribund until he acquired a powerful theory, largely equivalent to structure theory, which he then exploited with energy and mastery. He transferred to Leipzig in the middle of the period of his greatest productivity. The sudden and dramatic change in institutional setting, resources, and numbers of students—nicely paralleling the maturation of the field of organic chemistry in Germany—made remarkably little difference to his success rate and overall standing in the field, or even to the productivity of his group research if measured by a proper (intensive) yardstick. Productivity and standing only began to decline when Kolbe began to focus exclusively on those points of difference between his and the structuralists' theories.
In this context, it must be reiterated that Kolbe's theoretical approach was so distinctive as to be characteristic of only himself, for he did not convince even his students of the advantages of his approach to the study of chemical constitutions. Kolbe's ideas were not powerful in comparison to those of his competitors at other universities. To speak more precisely and with only a touch of hyperbole, the ideas were powerful only to the extent that they happened to coincide with structuralist notions. The projects that were predicated on Kolbe's conviction of a difference between carbon valences, on a
denial of chain formation, on his trimethine-trimethane benzene theory, or on the uniqueness of the Stammradikale , all proved scientifically sterile.
Here, finally, is the principal reason why the Leipzig research school was not more scientifically productive and influential. For Kolbe, at least, the focus should not be on distinctiveness as an advantage—especially not as an essential prerequisite for a successful school as some have viewed it—for we have seen that in this case his distinctiveness could only hurt him in the long run. Rather, attention needs to be directed to the power and empirical stature of the ideas driving the research. Kolbe's increasing concern—virtually an obsession—with precisely those details of his carbonic acid theory that proved most sterile ensured that his own research would be moribund. One consequence was that direction of the laboratory in more fruitful areas was left exclusively to junior associates, who were less able to lead and inspire. Another was that as Kolbe's stature in the field fell, his word meant less in recommendations for his students. The net result was that Kolbe's Leipzig school was gradually transformed from an exciting and productive example of group research into a combination of a quixotic personal research program of the director and an undistinguished mass-research group of a rather conventional character. What made his decline even more precipitous was the holy war he waged against his adversaries during the last sixteen years of his life.
The Crusade
Kolbe switched to the new atomic weights in 1868, at the same point that he decided to take a stand against the theory of chains, valence bonds, and benzene rings. Coincidentally, at the beginning of 1870 editorship of the Journal für praktische Chemie fell into his lap, which provided a bully pulpit for educating and haranguing the chemical world. He quickly penned a manifesto to open his first volume, then found repeated occasion during his first two years as editor to compare his views with those of the structuralists.
He now understood, correctly, that structure theory posited a sort of chemical "democracy," in which every atom is in principle as important as every other. Kolbe's own model was that of an army: a methyl group, for example, is like a "commando" unit consisting of a corporal (carbon) and three privates (hydrogen); in propane there are two more carbon atoms, but these are of higher rank than corporal and hence are chemically more central. The following year he used another metaphor, that of an autocratic state, which is effective precisely because it is hierarchical, in contrast to a democracy.[37]
At first, these discussions were carried on without evident rancor on either side. At the 1867 Naturforscherversammlung in Frankfurt, Kekulé treated Kolbe with extreme cordiality and Kolbe resolved privately to reciprocate in the future. By 1874, this was more difficult; at a chance meeting at a resort in Interlaken, Kolbe brushed off Baeyer's friendliness.[38] The transition appears to have been precipitated by national and personal events that occurred in 1870-1871.
Kolbe was unwell most of the summer of 1871, suffering from dizziness and nausea. Finally, he traveled to Marienbad for a five-week cure, which did him much good. Upon his return, he wrote Varrentrapp,
I used the involuntary leisure in Marienbad to give my chemical heart and conscience some relief and to expose the great flaws and weaknesses of the new chemical fashions. Much real mischief in this line is being done by both older and especially younger chemists, and since no one else is opening his mouth to stand up against this swindle, I have considered it my duty once more to burn all ten fingers by portraying this modern child in its true flaws.[39]
In this new essay, "Fashions of Modern Chemistry," Kolbe indicted structure theory for being at once too empirical and too speculative. The structuralists were overly schematic, hence guilty of "crass empiricism," in immediately turning to pencil-and-paper manipulations once they had an empirical formula. They failed to investigate the hierarchy of radicals forming a molecule, merely drawing pretty pictures that purport to explain all chemical relationships of the compound. At the same time, he thought, they were overly speculative in that they presumed to have the ability to specify spatial arrangements of the constituent atoms. Once he gave his amanuensis the empirical formulas for three novel compounds for which their discoverer had just assigned structural formulas. The man reported back in a half hour with several more candidate structures, some of which looked more probable to Kolbe. Kolbe concluded that structure theory is a dangerous toy, especially for inexperienced chemists, and that structures are often assigned "in one's sleep," with little or no empirical warrant.[40]
Privately, Frankland "entirely dissent[ed]" from this judgment:
[I]t seems to me that your experiment with your amanuensis resulted in a great triumph for these formulae; since, without any previous knowledge of the subject, he at once found the only possible constitutional formula for one of the compounds whilst his formulae for the two others would be at once modified by a chemist as unnecessarily complex. Surely the more simple, & free from possible misconstruction, such formulae can
be, the better. And I think they are generally used by chemists, not as means of investigation but as expressions of the writer's ideas of the constitution of the bodies he is describing· But even as instruments of investigation they are not altogether useless . . .[41]
Volhard also objected privately; he joined Frankland in expressing regret over the personal character of many of Kolbe's remarks. Kolbe's response was straightforward:
Scientific matters must not be taken personally. I cannot help myself, I must criticize and contest the chemical ideas that I consider false and worthless, just as I tolerate others' opinions, and I am happy to see my views contested, when the controversy is pursued in a gentlemanly fashion. Science always benefits from that. . . . You say that my critiques will only succeed in gradually alienating all the chemists of Germany. That may be the case, if not for all, at least for many, i.e., for some time; but I ask you, did Liebig ever hesitate to express his convictions, in critiques and otherwise, for fear of thereby alienating many?
As he later wrote Varrentrapp, he would rather be considered sharp-tongued than cowardly.[42] He now fulfilled a longstanding desire to follow the examples of Berzelius and Liebig by starting a series of annual critical retrospective essays, published each December in his journal. These gave him additional opportunities for spicy polemical harangues.
In Kolbe's third and fourth retrospects, those for 1873 and 1874, he went after his favorite example of structuralist excess: Kekulé's benzene theory. He absolved Kekulé himself of much of the blame,[43] for he was convinced that Kekulé regarded the theory merely as an intriguing and useful hypothesis. However, most chemists by this time viewed the hexagon as "infallible dogma," as "the Pope is for Catholics." They were true fanatics, Kolbe wrote, and viewed him (Kolbe) as a rank beginner, of weak understanding. They were right, he thought, for he could not understand arguments built "in the air" or "on loose shifting sand." The end of their sand castles was not distant. Kolbe continued,
The modern chemist, who knows exactly what a chemical compound looks like in its middle and its end, how the six carbon atoms of benzene are symmetrically linked together in a plane, who then further purports . . . to have a clear conception of the spatial arrangement of the atoms, of their ortho, meta, and para positions, who determines the positions of all of the atoms in the compound, has long since abandoned the solid ground of exact science; the scientist has become a metaphysician. Rhetoric which is bereft both of content and of value but which sounds profound has begun to displace solid research and sober judgment.[44]
Kolbe later developed this image by defining true physicists as "ortho" physicists, versus "paraphysicists" who pursued fanciful notions such as kinetic theory and metaphysicists who have no use whatever for experimental confirmation. In his own view, he was an "orthochemist" and Kekulé was a "parachemist."[45]
Kolbe found his ideal model for the "metachemist" pursuing "transcendental chemistry" when the then-unknown J. H. van't Hoff unveiled his theory of the asymmetric carbon atom, the first step toward chemistry considered in three dimensions—soon to be called stereo-chemistry. Van't Hoff, who had studied with Kekulé and Wurtz, first found employment at the Utrecht Veterinary College; in 1878 he was appointed at the University of Amsterdam. A sketch of the theory was published in Dutch in 1874, and a longer French version appeared the next year. The first enthusiastic advocate of van't Hoff's theory was Johannes Wislicenus, professor at Würzburg, who was a mid-career structural organic chemist with a fine reputation; he had even published some thoughts on three-dimensional (physical) isomerism himself. Wislicenus asked his student F. Herrmann to prepare a German translation of van't Hoff's "Chemistry in Space," wrote an enthusiastic preface, and sold the work to Vieweg Verlag.[46] Kolbe found out about this translation almost immediately because the Vieweg company had a long-established policy of automatically sending proof sheets of all their organic-chemical publications to Kolbe.[47]
Kolbe was not a happy man at this time. Suffering repeated bouts of ill health himself, he had seen in the past few years the deaths of many of his closest friends and relatives: Otto Erdmann and Eduard Vieweg in 1869, F. J. Otto in 1870, his own father also in 1870, and Liebig in 1873. By far the hardest blow was the death from cancer of his beloved wife on 26 December 1876. He heard about Franz Varrentrapp's death on 3 March 1877, while he was still severely depressed about his wife. Kolbe was close to sixty himself, exhausted and in poor health. To Heinrich Vieweg's business manager Herr Lücke Kolbe wrote, "The older one gets, the more frequently one looks around himself in the circle of his friends and close relatives, watching Death carry out his sad and terrible office, until one's own turn comes around."[48] After losing out to Baeyer as Liebig's successor in Munich (1875), Kolbe knew that he was in Leipzig for the duration.
It was in such a mood, no doubt feeling that he no longer had anything to lose or anyone to please, nor any time to waste, that Kolbe sat down to compose under the heading "Sign of the Times" a thundering reproof against van't Hoff and Wislicenus, a devastating critique that would once and for all extirpate this "cancer" of structuralism (for that is what he considered and named it). Using another pathological
metaphor, he claimed that modern chemistry was nothing less than a revisiting of Naturphilosophie , the "plague of the century" as Liebig called it, promoted by pseudoscientists who wish to smuggle their wild notions into the science, like introducing a fashionably dressed prostitute "into good society where she does not belong."
Whoever thinks this worry seems exaggerated should read, if he is capable of it, the recent phantasmagorically frivolous puffery . . . on "The Arrangement of Atoms in Space." . . . A Dr. J. H. van't Hoff, of the Veterinary School of Utrecht, finds, it seems, no taste for exact chemical research. He has considered it more convenient to mount Pegasus (apparently on loan from the Veterinary School) and to proclaim in his "La chimie dans l'espace" how, during his bold flight to the top of the chemical Parnassus, the atoms appeared to him to be arranged in cosmic space. The prosaic chemical world had no taste for these hallucinations, so Dr. F. Herrmann, assistant at the Heidelberg Agricultural Institute, undertook a German edition to give the work a wider audience. . . . It is typical of these uncritical and anti-critical times that two virtually unknown chemists, one of them at a veterinary school and the other at an agricultural institute, pursue and attempt to answer the deepest problems of chemistry which probably will never be resolved (especially the question of the spatial arrangement of atoms), and moreover with an assurance and an impudence which literally astounds the true scientist.
These notions would have been quietly buried, Kolbe noted, had not a chemist of reputation, Wislicenus, taken van't Hoff under his wing. Wislicenus had thereby placed himself in imminent danger of squandering that reputation, of no longer being considered a true scientist but a "spiritist of the first water."[49] To his friend the publisher, Kolbe was unrepentant, for he wrote Heinrich Vieweg that his critique could only increase sales. "I don't understand Wislicenus," he added. "Sometimes I fear that he may not be of sound mind."[50]
Wislicenus was understandably upset. A fundamentally kind and broadminded man, he wrote Kolbe a long, emotional letter, trying hard not to show open anger.
You cannot possibly have studied van't Hoff's essay . . . [for] how else could you have reproached me (by logic I do not understand) for a tendency toward spiritualism, or held against the young van't Hoff his position at a veterinary school, or against the translator Herrmann, who was my assistant and solely due to pressing external circumstances accepted a position at the agricultural institute in Heidelberg! I have never doubted that it is a holy zeal for the truth that guides your critical pen; but on the other hand I regret that you do not seem to concede any possibility of your own fallibility, which everyone must grant. . . . I
know that I can err, but I also know that I have no cause to allow myself to be struck from the ranks of exact scientists, for I as well as you have the will to serve the truth . . .[51]
Van't Hoff responded publicly, and very effectively, in the pages of the Berichte :
A theory that so far is contradicted by no single fact can only be further examined experimentally. Thus when someone, even so fine a chemist as Kolbe, avers that a chemist who is not yet well known and who is employed at a veterinary school should not bother himself with theories . . . I can only say that such behavior fortunately is not a sign of the times, but rather must be regarded as a contribution to understanding a single individual.[52]
Kolbe's critique of van't Hoff was his most famous diatribe, certainly his most humorous, and one of his most vicious. It was at this time that many began to wonder if Kolbe had become mentally ill.[53] Whether literally ill or not, there is no question that he was sick at heart at what he saw happening to his beloved science. To be sure, he was not alone in thinking that structural chemists often went overboard. The following October he had a conversation with his old mentor Wöhler, during which Wöhler commented that "what is published these days as chemistry, is not chemistry at all." However, when Kolbe pleaded with him to allow his words to be quoted directly, Wöhler quickly and strongly demurred, saying that he hardly even read the literature any more. Kolbe responded that he didn't either, and had just as little understanding of "modern" chemistry. Similarly, Kolbe urged his true Doktorvater Bunsen, who was likewise sympathetic with Kolbe's position, to stand with him against the structuralists, but Bunsen also firmly declined, even (like Wöhler) to have his name mentioned. With Berzelius and Liebig dead and Wöhler and Bunsen unwilling even to be named, Kolbe felt very much alone.[54] Ernst von Meyer, Kolbe's loyal assistant and loving son-in-law, became co-editor of the Journal für praktische Chemie at the beginning of 1879 and, as he later related, often tried to exert a moderating influence—only occasionally with success.[55]
Wislicenus' and van't Hoff's complaints may have had some influence, at least in redirecting Kolbe's fire toward more prominent chemists. Kolbe decided, after all, that the only way to destroy the weed was to get to its roots, so from this time on he went right after Kekulé, as well as Kekulé's most famous student, Baeyer. Seven months after the van't Hoff polemic, Kolbe published a "Confidential Letter to Professor Kolbe," purportedly written by a structuralist
named "Dr. R.," but in fact written by himself as a parody of structure theory.[56] Kekulé, whose recent rectoral address at Bonn (18 October 1877) was well roasted in the piece and who could easily divine the real author, wrote an "open letter" in rebuttal and asked Kolbe to publish it. To twist the sword in the wound as best he could, Kekulé pretended ignorance of the identity of "Dr. R." and added that, in contrast to Dr. R., he should be identified as the author of the rebuttal, for "I have always been of the opinion that anyone who respects himself must also have the courage to accept responsibility for his actions and words." He then said that he did not doubt that Kolbe would print the piece, knowing Kolbe's sense of fair play.[57]
Kekulé had trapped Kolbe, but Kolbe was resourceful and squirmed away. As it happens, he had just composed a "Critique of Kekulé's Rectoral Address," and so he published this together with Kekulé's rebuttal in the same issue.[58] Kolbe now really let loose. Kekulé's speech was poorly constructed, he said, almost illiterate, the obvious product of a former Realschüler ;[59] Kolbe cited a number of what he thought were egregious solecisms. More substantively, Kekulé's chemistry was not only colored by "crude Haekelism" but was also filled with "wild phantasies without any real basis." His latest hypothesis of intramolecular atomic vibrations illustrated to Kolbe "to what monstrosities an intellectually gifted man can let himself be carried, who has not learned early to order his thoughts, to think logically, and to rein his imagination." He twice ridiculed Kekulé's "chemical dreams" and concluded by offering a "dream" of his own. The carbon atoms of benzene, you see, are constrained by three bonds each, so they must move in the fourth dimension! "Das ist meine Theorie, " Kolbe proclaimed triumphantly, but confessed that he had not the courage to develop this idea any further, so he would leave it to the "most modern chemists" to do so.[60] Graebe was dismayed by this article. He wrote Rudolf Schmitt, "I always regret that such a significant scientist, who is personally so amiable, puts himself in such a false light with articles like this. Those who don't know him imagine him to be an unpleasant person."[61]
A few months after this episode, Kolbe found occasion to heap ridicule on Baeyer in a similar fashion. Baeyer had given an address on chemical synthesis in honor of King Ludwig's thirty-second birthday, in which he portrayed for a lay audience some of the leading ideas of recent chemistry and physics. To make the concepts accessible, he eschewed scientific terminology and epistemologically cautious circumlocutions, speaking, for example, of valence bonds as analogous to "fishhooks," atomic "glue," and so on. In his published critique, Kolbe made much of Baeyer following his teacher's example—the speech was
just as baroque, illogical, and dreamlike.[62] He wrote Wöhler, "I'm no spiritist, but I would not have been surprised if Liebig's ghost had seized him by the collar after this speech and thrown him from the podium as an unworthy successor." He told Frankland to read it for amusement—"much wilder than Kekulé's rectoral address . . . I think my critique will somewhat ameliorate his obscurity; Kekulé has also already become tamer." He thought Baeyer might be suffering from softening of the brain or megalomania.[63]
Volhard, like Graebe, was appalled by Kolbe's attacks and wrote his former mentor: "I ask you please for all the world no more critiques like that of Kekulé's rectoral address! I cannot agree with this critique in any way." He pointed out that an annual address is compulsory for the university's rector and that it must be directed to a lay audience; consequently, "es ist nicht fair zu kritisieren" as if it were a chemical treatise.
And as for the form, I ask you: What do you care about Kekulé's style, or his classical education? Consideration for K's scientific accomplishments, indeed mere collegial respect ought to have stopped you from treating this man as if you were a teacher looking over a schoolboy's assignments and correcting his mistakes. . . . I beseech you, no more such intemperate critiques! More tolerance and respect for scientists who have made and are still making their contributions!
Volhard was a good friend who had enormous respect for Kolbe; indeed, he regarded Kolbe as one of the greatest chemists of the century, and Kolbe knew it.[64] Kolbe also liked and respected Volhard. Only such a man could direct such words to Kolbe.
Even so, they put Kolbe in a rage, answering Volhard with visible effort to control his pen. It particularly galled him that Volhard had accused him of being unfair , when in fact he was placing himself bravely and alone in the line of fire for the sake of his beloved science, while Volhard and everyone else were sitting comfortably on the sidelines. This time there were no horsey metaphors, but sexual, militaristic, religious, and political ones. Kolbe wrote,
Your letter troubled me, for I see from it that you now number yourself among the (in a word) weaklings who are not troubled when our chemical social democrats, Kekulé and Baeyer, slap the face of our science and soil it, but who break out in a sweat when a pure hand is raised to put a stop to it. . . . I cannot sit quietly and see these two make our science a footstool of their vanity and misuse it to satisfy their arrogance. Have you too really come so far in these feeble materialistic times that you can no longer be inspired by higher goals, by ideals? . . . Believe me, I enjoy criticizing; can you not imagine, since all others out of convenience or
cowardice are silent, that someone feels the calling and the obligation to science to stand up for it publicly? . . . I close by assuring you that wherever our science is violated you will always find me, as long as I have the power, as the first of her defenders.[65]
Kolbe was increasingly frustrated. He continued to write to friends, seeking comrades for his crusade, but found at best silent support, more commonly demurs and even rebukes. These made no difference to his actions, for he became if possible even more personal. One of his favorite hobby horses in the last few years of his life was linguistic critiques. Kolbe was an excellent writer; however, he harbored the common delusions (consistent with his conservatism in other areas) that there was a happy time, long before the present corrupt age, when all educated people wrote "classic" German, and that philology was properly a prescriptive rather than a descriptive enterprise. In some cases his remarks were well founded, even if petty and unnecessary; in other cases he was simply closed-minded and parochial.[66] He often exclaimed m print, sarcastically remarking on his victims' lapses, "This is how a professor at a German university writes!" He also campaigned against Realschulen, for he was convinced that only exposure to classical neohumanism in the traditional Gymnasium could truly educate.
Kolbe's old friend and comrade-in-arms Frankland provided the final straw. The first sign of real trouble was when Kolbe heard that Frankland was sending his ion Percy to study with Wislicenus, rather than with him or Bunsen. Kolbe could hardly believe it. Wislicenus "has long since ceased to be an exact scientist, but rather is a Naturphilosoph, a metaphysician"; a boring chemist, even if a fine man.[67] Then Kolbe found out from reading proofs from Vieweg that, in a historical introduction to Roscoe and Schorlemmer's major treatise of organic chemistry, they had uncritically accepted Kekulé's view of the last forty years. This was highly worrisome to Kolbe, for Roscoe and Schorlemmer had both been Bunsen students, and the inorganic portion of their textbook had already proven to be influential. He fired off a letter to Roscoe. "Kekulé has deliberately falsified history, in order to place himself and the French chemists he is so fond of in the foreground." It is Frankland and he, Kolbe continued, who deserve credit for valence theory. Moreover, Kekulé is uneducated, cannot think clearly, lies, steals, and seeks to derogate and slander great men such as Berzelius. His Lehrbuch is the "worst textbook that we have." Roscoe sent Kolbe's letter to Schorlemmer, who was simply amused, and thought Kolbe to be "mad as a march-hare." His accusation that Kekulé had stolen carbon tetravalence from him and Frankland was "best proof that he is mad!"[68]
Having failed to receive satisfaction from Roscoe, Kolbe now set to work to fight the historical record, also with the intent of defending Frankland. He wrote a long essay on "My Participation in the Development of Theoretical Chemistry" and published it piecemeal in his journal.[69] Here he portrayed the whole of modern chemistry as a highly injurious product of the unscientific and sterile French chemistry of Dumas, Laurent, and Gerhardt. Kekulé, Baeyer, Wislicenus, Fischer, and others had substituted flights of fancy and the painting of pretty pictures for the exact scientific principles that Berzelius had introduced into chemistry and whose further development had been due to such men as Liebig, Wöhler, Bunsen, Frankland, and himself. Kolbe felt that his seminal work had been systematically ignored by the structuralists—which is not far from the truth. He did not hesitate to accuse Kekulé of both the largest and the smallest transgressions: he repeatedly and explicitly proclaimed that Kekulé's conduct could only be viewed as intentional usurpation of the theories of others, then added insult to injury by filling page after page with stylistic criticisms. He even cruelly drew attention to Kekulé's premature aging, which he maliciously ascribed to his guilt for self-consciously leading German chemistry down the structuralist cul de sac.[70]
As for structural formulas, he characterized them no fewer than three times as "grob sinnlich" (coarsely sensual) and materialistic, moreover, as a symbol of an unachievable goal.
The sober prudent scientist will tell [Kekulé] that the object for which he and the majority of modern chemists strive is a chimera, that we will never succeed in gaining a conception of the arrangement of the atoms in the molecule, and that chemists should set for themselves a more modest goal: the investigation of chemical constitution in the sense of Berzelius . The goal for which Kekulé strives, and which he considers accessible, is actually even more inaccessible for us than the moon, for we can see the moon and determine its form, but atoms we cannot see, and their form is perceivable with none of our senses.[71]
These words were echoed (and partly contradicted) in the foreword to Kolbe's abridged organic chemistry textbook, written in February 1883. Structural formulas are mechanical and coarsely sensual, a symptom of the modern "crassly materialistic treatment of scientific matters; the latter ought to be conceived by the mind and not mechanically."[72]
Having defended Frankland's priority, Kolbe now tried to get him on board. He asked Frankland for permission to title the brochure version of his essay "Frankland's and My Participation in the Development of Theoretical Chemistry." Frankland had no objection, as long
as Kolbe would state clearly in the preface that he alone was responsible for the contents. Kolbe was taken aback at this request and withdrew his suggestion. "Why are you so fearful? You want me to pull your chestnuts out of the fire; I do not hesitate to do that, having no fear of the fire of truth. . . . We should have stood up against the insolent behavior of these people years ago. But perhaps even now it is not too late."[73] Now it was Frankland's turn to feel a bit insulted. He replied that he was perfectly capable of taking care of his own chestnuts; indeed, he had been the first, four years earlier, to assert his and Kolbe's fight to valence theory; but by "mixing up Dumas and Wurtz with the protest," he felt (no doubt rightly) that this would weaken the case that needed to be reiterated.[74]
Here the matter rested for two years. Finally, Kolbe dusted off the chestnuts once more and wrote his friend. "If only other chemists, and above all I am thinking of you, would not always leave me alone to pull the chestnuts from the fire, but would instead come to my aid in energetically fighting Baeyer and the thoughtless hollow schematism of structural chemistry." We could "finish Kekulé off" once and for all, Kolbe promised, and show structuralism for the humbug it is. Frank-land was incredulous.
Your letter astonished me not a little for it had never entered my head to imagine that you could for one moment think of me as in any degree an antistruktur Chemiker. Still less that you should think of me as one likely gegen die Strukturchemie "energisch zu kämpfen " or as one sharing your opinion that die Strukturchemie ein Humbug ist! Turn over the leaves of my "Lecture Notes for Chemical Students" and you see Strukturchemie in its extremest development on almost every page! . . . That there should be no more such mistake in future, I here record my Glaubensbekänntniss: Chemistry owes its progress from empiricism to exact science entirely (so far as theoretical conceptions are concerned) to Strukturchemie. Without Strukturchemie there is no science of chemistry . And allow me to add,—two of the first Strukturchemiker to whom this progress is due were Berzelius & Kolbe![75]
And now it was Kolbe's turn to be astonished. Who had seduced his friend (or, rather, former friend), "you , who were once upon a time, with me, a champion of positive exact chemistry," into becoming a "spiritist"? Did not Frankland remember those golden days of great scientific discovery in Marburg? And now Frankland had not only turned tail, but had insulted Kolbe by branding him with the despised epithet "structuralist." "I now see that we do not understand each other."[76] This was the end of their correspondence.
Neither Kekulé nor Baeyer ever really responded to Kolbe's insults. Kekulé wrote up a long response, and sent it to his friend Volhard, then editor of the Annalen . Volhard strongly urged him to withdraw it.
Don't you see that you will only thereby legitimize his attack, which can only properly be condemned by maintaining silence. You may be sure that no one will welcome your defense more than Kolbe himself, for it would finally break this terrifying silence, and give him the opportunity for a salty reply. And, as before, you will be sure to draw the short end of the stick, for you are no match for Kolbe when it comes to coarseness and ruthlessness.
"That's what I call friendship," Kekulé gratefully replied, and took Volhard's advice.[77] As regards Baeyer, Volhard again offered advice and consolation, this time to Baeyer's wife.
My old friend Kolbe is behaving truly irresponsibly. A pity on the man; since he began to devote himself to insults he has produced nothing more of value. Moreover, one is in good company when one is up-braided by him, so one may always console oneself this way. Everyone who has achieved some reputation in science should take K. as a cautionary example: he believes it sincerely, considers it his duty to behave this way; he does not see what immoderate overestimation of himself is involved, although he is otherwise a very clever and intelligent man.[78]
As Volhard had predicted in 1876, Kolbe had now succeeded in alienating himself from most prominent German chemists, including several hitherto good friends (we will see how he and Hofmann parted ways in the next chapter). Volhard was still left, but not for long. On 20 July 1884, they had a conversation during which apparently they could agree on nothing; Kolbe's letter the following day (one of his last surviving letters) complained that Volhard, too, had now been "badly infected by Kekulé's and Baeyer's dogmas."[79]
Kolbe had other shocks as well. Even after his devastating denunciation of van't Hoff's small book, Heinrich Vieweg accepted a larger work by the same author, Ansichten über die organische Chemie , just a year later. ("The greatest nonsense I have ever read," fumed Kolbe to Vieweg. "The author is definitely out of his mind, ready for the madhouse.") Then Vieweg selected Wislicenus to edit—and structuralize!—Strecker's organic chemistry, which had been Kolbe's favorite text. Kolbe was appalled at this "disfigurement." He feared that Wislicenus might be called to Halle as Heintz' successor, thus making him a close neighbor (in fact, Volhard was called to Halle, but Wislicenus became Kolbe's successor three years later!). The Hand-
wörterbuch der reinen und angewandten Chemie , for years Kolbe's brainchild, had long since become a structuralist reference work. Kolbe made Vieweg add a clause to his contract for his own Kurzes Lehrbuch der Chemie , stipulating that in the event of his death, Vieweg would not choose a structuralist editor.[80] He now knew that he would not live to see the revolution that for the last quarter century he had been predicting as imminent. "We live now in a time of barbarization [Verwilderung ] in chemistry, like never before," Kolbe mused sadly. "Soon the crash will come, and then the loudmouths will vanish from the scene."[81]
The last meeting between Kekulé and Kolbe was bitter, although Kolbe enjoyed every moment. On 4 April 1884, Kekulé and his wife arrived at a resort (in Bodighera, on the Italian Riviera) where Kolbe also happened to be vacationing. "You should have seen his pale, frightened face the next morning . . . when he first saw me," Kolbe wrote his nephew. "He is an old man , stooped over; I would never have recognized him had I not known it was him." The Kekulés had intended to stay a week, but left after three days: "I smoked him out," Kolbe related gleefully.[82] Kekulé was then fifty-four, Kolbe sixty-five. We do not know Kekulé's reaction when he heard of Kolbe's death seven months later.
It is now time to take a step back from the fray and directly ask an important question that we have been skirting. Was Kolbe simply a sour old man whose crusade was motivated by an irrational obsession or monomania (as Armstrong later called it)—in short, was he acting as a poor scientist? As much as this places one under vehement suspicion of Whiggery—for Kolbe was so unfortunate as to contest much of what constitutes organic chemical theory today—it is difficult to avoid giving an affirmative response to this question. In defending oneself from Whig opprobrium, one might note that as regards contemporary opinion after 1870, Kolbe lost nearly all of his specific factual arguments and convinced absolutely no one of the truth of his modified radical theory of organic constitutions, even his own students and closest friends. Moreover, the previous discussion has shown that he himself recognized the completeness of his defeat by the time of his death.
That said, it must be noted that while most of Kolbe's theoretical affirmations after 1870 were unsuccessful, by no means did all of his criticisms of his opponents miss the mark. We have seen that Kolbe had substantial silent support for many of these criticisms among such men as Liebig, Erdmann, Varrentrapp, Wöhler, Bunsen, Beilstein, Erlenmeyer, Frankland, and even Volhard and Lother Meyer on occasion. I have found no Kolbe correspondent who denied that there was
a great deal of inferior, sloppy, and excessively conjectural work being published, and they all agreed that the amount of such unsatisfactory research was increasing. (Volhard believed that this had nothing to do with structure theory but rather simply with the great expansion of the field; it was no longer a self-selected elite group, as it was a generation earlier, but a mass of average workers creating mass-produced science.[83] ) In fact, Kolbe was justified in his accusation that structural formulas were sometimes bandied about thoughtlessly and superficially, with little regard to empirical evidence and reasoned justification.[84]
Of course, the same charge could be laid at Kolbe's door, to the extent that he may be considered a structural chemist himself. Was he? Contemporary opinion on this point was unanimously in the affirmative, not only in the view of structuralist opponents such as Kekulé, Wislicenus, Lothar Meyer, and so on but also in the opinion of those who knew him best: his students, former students, friends, colleagues, and family members, including Frankland, Claus, Crum Brown, Volhard, Ernst von Meyer, and Ost.
But despite this unanimity, the assertion is not strictly true. To be sure, Kolbe's views and those of the structuralists coincided on many points, and formula translation was always possible between the two systems. However, there were also real differences, as I have been at pains to argue in this and the preceding five chapters. In the course of his career, Kolbe made many predictions of the possible existence of new compounds and new isomers; some of these predictions were fulfilled, some were not. Some of his predictions were fully equivalent to those of the structuralists, while some highlighted the distinctions between the two systems. It is remarkable that every time Kolbe attempted a crucial test, that is, of a prediction of the latter type, the result disappointed him.
Let us review some examples, most of which we have seen before. As early as 1857 and 1858, Kolbe was predicting the existence of a variety of isomers of alcohols, glycols, acids, and aldehydes, including isomers of oxalic, glycolic, and lactic acids. He thought that Wurtz' glycol ought to be dehydratable to aldehyde, but that it could never be oxidized to an acid. In his 1868 treatise, he predicted two isomeric propylenes and no fewer than fifteen isomeric pentanes.[85] He tried to find an isomalonic acid and a second carbon oxysulfide, and he thought that a chemical distinction between the two chlorine atoms in 1,3-dichloropropylene ought to be demonstrable. He looked for reduction products of benzene, an isomer of benzene, and isomers of all monosubstituted benzenes, and he thought there should be four isomers of each disubstituted benzene. He was able to find none of these compounds or reactions.
Kolbe was continually predicting isomers in excess of those envisioned by classical structure theory because of his hierarchical view of organic molecules (each carbon atom in a molecule, considered as the Stammradikal , should give rise to a distinct series of isomers) and because he was convinced that the four valences of carbon were intrinsically distinct. Chemists of the 1860s and 1870s were already being deluged by a flood of new isomers, and most greeted the apparent proof of equivalence of carbon valences with considerable relief. But Kolbe simply refused to accept the evidence provided by the nonexistence of isomers. This was true even though many positive refutations of his predictions emanated from his own laboratory (for some examples, see note 36 in this chapter). Logically, his position was impeccable: the missing isomers are simply too labile to be isolated, transforming themselves into known isomers before they can be characterized; or we simply have failed to find the right reagents or conditions to produce them. But the accumulating empirical evidence became more and more difficult to ignore or brush aside. It is little wonder that he was unable to convince his colleagues in the field, and even his own students, of the advantages of his system over that of the structuralists.