Pedagogical Reform

Associated with the reform of the German universities in the early nineteenth century was a gradual change of opinion that came about in how best to teach in the universities. The change was most dramatic in the natural sciences and medicine, where an empiricist-sensationalist epistemology derived from leading Enlightenment ideas led to less reliance on lectures and lecture demonstrations and eventually dictated laboratory-based instruction for most students in the sciences. In this new movement, some historians have emphasized the role of eighteenth-century pedagogical reformers such as Johann Heinrich Pestalozzi,^[5] while others have tried to trace the change to early philological and historical seminars at late eighteenth-century modernist universities such as Göttingen. The humanist seminar has been an appealing historical model because it was there that the new research-oriented scholars tried to create a monism from their dualist activities, by interesting their students in research problems and making research a routine aspect of pedagogy, at least for selected advanced students.

Recent work has, however, cast some doubt on a simple evolutionary model from the humanist seminar to the scientific laboratory-based university institute.^[6] One problem in making this connection has been reconciling it with the atmosphere of the aggressively idealist, non-utilitarian and nonmaterialist neohumanist rhetoric of the day and considering the popularity in Germany of a speculative and nonempirical Naturphilosophie movement. Another problem has been the recognition that most of the early institutes and seminars (i.e., those

before about 1820) were not in fact research oriented but were instead largely propaedeutic in nature.^[7] Moreover, a distinction needs to be made between the introduction of laboratory research for the professionalizing elite student, which occurred early, and laboratory work for all, including average students studying ancillary disciplines.^[8] This latter pattern of the scientific teaching laboratory did not emerge until relatively late; the first models were only created in the 1830s. The pioneering field in this development was chemistry.

A useful way to begin to describe the way these events came about is to discuss briefly four of the leading protagonists in this sea change. In addition to some curious commonalities in their backgrounds, all had a decisive influence on the young Hermann Kolbe—who will be more formally introduced in the next chapter.

Jacob Berzelius

Berzelius (1779-1848)^[9] was the sort and stepson of Lutheran country pastors, from whom he imbibed a dose of theism strongly moderated by late eighteenth-century rationalism and materialism. His education was fully in the spirit of the Gustavian Swedish Enlightenment and was much influenced by French ideas. During his years as a medical student at the University of Uppsala, he found himself "irrevocably gripped" by the love of chemical experimentation. Although to a certain extent an autodidact in chemistry, he learned the French antiphlogistic chemistry of Lavoisier and Fourcroy from his professors, in particular A. G. Ekeberg and Pehr Afzelius. He also consorted with liberal and progressive circles at the university. He graduated from Uppsala in 1804, at which time he became an adjunct (similar to Privatdozent) at the Stockholm School of Surgery—later the Karolinska Mediko-Kirurgiska Institutet—and a physician for the poor. In his meager spare time, he pursued an increasingly successful experimental research program. In January 1807 Berzelius was appointed professor at the school, and he remained in this position for the rest of his life. It was significant that Berzelius spent his career in a professional school, not a university; it required him to remain close to the practical and empirical level, consistent with his innate inclinations. In the 1820s Berzelius fought unsuccessfully for legal equivalence of the Karolinska Institutet with the Swedish universities and urged a more utilitarian and modernist university curriculum. He also fought the phosphorist school, a Swedish version of Naturphilosophie that was influential in the first quarter of the nineteenth century.^[10]

Berzelius' first love was physiological chemistry, but he soon discovered stoichiometry and atomic theory. His utter brilliance as a bench

chemist, his theoretical talent, and his extraordinary capacity for work led to a variety of fundamental contributions in both of these areas by 1812, although most were published only in Swedish and so were little known outside of the country. In the summer of 1812 he spent four and a half months in England; in 1818-1819 he spent almost a year in Paris, also visiting Great Britain and Germany. Other trips followed. These foreign travels, and the consequent translations of his books and papers into the major European languages, effectively spread Berzelius' ideas, and by 1820 he was recognized internationally as one of the greatest of living chemists. It is largely to Berzelius (and mainly during these years) that we owe the successful elaboration of atomic theory, as well as the initial stages of development of experimental and theoretical organic chemistry from the base established by Scheele, Lavoisier, Fourcroy, and Gay-Lussac.^[11]

Berzelius' reputation was even further enhanced during the 1820s. It was only after 1820 that reliable and full translations of his monumental textbook began to appear, which was first begun in Swedish in 1808. A new edition, edited from 1825 on by Friedrich Wöhler, appeared first in German, the Swedish version following along behind. This edition was the first by Berzelius to treat organic chemistry in detail; the two organic volumes can be viewed as the first full-length organic chemistry textbook in history. Moreover, Berzelius' new position as Secretary of the Swedish Academy of Sciences brought with it an obligation to write an annual report on the progress of chemistry in all subfields throughout the world. The first of these reports, for the calendar year 1820, was quickly translated into German, and a pattern was established that persisted until Berzelius' death. The size of these reports, usually known by their German name Jahresberichte , gradually increased until they were the size of substantial books. In the 1820s, Berzelius was at the top of his form and he knew it. His magisterial judgments of his colleagues' work in the reports were closely followed and highly respected. Berzelius had become the supreme judge and legislator in his science, the one man whose word mattered to all.

An additional factor promoting Berzelius' high standing in Germany was his practice of accepting selected applicants for advanced work in his laboratory. His second guest worker, and the first non-Scandinavian, was C. G. Gmelin in 1814-1815, who later became a professor at Tübingen. Closely following Berzelius' first visit to Germany came the young Eilhard Mitscherlich and the brothers Heinrich and Gustav Rose, all from Berlin and all in 1820-1821. Mitscherlich's visit resulted from the circumstance that Altenstein had offered Berzelius the chair of chemistry at the university, vacated by Klaproth's

death in 1816. Berzelius declined; at least six others were then offered or were considered for the chair, including Stromeyer and Leopold Gmelin. Asked his advice during his visit to Germany in 1819, Berzelius recommended Mitscherlich, whom he had only just befriended. Altenstein agreed, but with the proviso that Mitscherlich should first study with Berzelius in Stockholm. The Rose brothers' trips were also related to this connection, as well as to their friendship with Mitscherlich.

At most, Berzelius accommodated two or three guests in his laboratory, and he often had none at all. Systematic instruction was not given; rather, Berzelius allowed visitors to follow their own research ideas, simply giving advice whenever it was desired. In addition to the four Germans just mentioned, Wöhler came to Stockholm in 1823-1824 and Gustav Magnus, another Berliner, in 1827-1828. By 1830 Justus Liebig could be considered a disciple of Berzelius, even though he had not studied directly with the master; a few years later, Robert Bunsen joined the Berzelians, again in spirit if not in the flesh in Stockholm. German chemistry was thus strongly infused with Berzelian ideas in the 1820s and 1830s, through both direct and indirect channels.

By the late 1830s, however, Berzelius was in a theoretical retreat, most noticeably in the field of organic chemistry, largely because of the experiments and ideas of upstart French chemists such as J. B. Dumas, Auguste Laurent, and Charles Gerhardt. A sense that Berzelian chemistry was passé gradually took root in Germany as well, certainly well before Berzelius' death in 1848. Berzelius himself, who gave up most laboratory work by about 1835, grew increasingly inflexible and cantankerous. His opinions were always freely and openly expressed in his Jahresberichte , and they created much ill will among those whom he attacked—above all, the French chemists, but also his hitherto devoted admirer Liebig. His most loyal disciple and friend, however, was Wöhler.

Friedrich Wöhler

Wöhler (1800-1882)^[12] was the son of a Hessian agronomist and veterinarian, and he grew up near Frankfurt. After attending the Gymnasium there, he entered Marburg University in 1821 with the intent of studying medicine. His passion from early childhood, however, had been chemical experimentation and mineral collecting, and Ferdinand Wurzer's lectures did not attract him. Accordingly, he transferred to Heidelberg to study with Leopold Gmelin. But Gmelin judged that Wöhler already knew too much chemistry to profit from his courses; he advised Wöhler to study with Berzelius after receiving his M.D. de-

gree. In the fall of 1823, upon receiving a favorable response to his inquiry from Stockholm, Wöhler took this step. It determined the course of his life.

Wöhler not only learned Berzelian techniques in his year in Stockholm, he also learned fluent Swedish and formed an extremely close friendship with the older Swede that lasted until Berzelius' death. Berzelius eventually urged the familiar form of address upon his student—for the time, an unusually strong mark of regard of an older for a younger man. Back in Germany, Wöhler sought habilitation at Heidelberg, but was instead hired for the new Berlin Gewerbeschule (trade school) at a salary of 400 thalers. Three years later, he had become a highly respected chemist and was earning 1200 thalers.^[13] By this time he had also become Berzelius' viceroy in Germany by translating and editing the German editions of Berzelius' Jahresberichte and Lehrbuch —an average of about one and a half large volumes of text per year for over twenty years.

Late in 1831 Wöhler accepted for personal reasons a call to the newly founded Technische Hochschule (Institute of Technology) in Kassel at a diminished salary of 800 thalers plus free rent. There he continued the experimental work that he had begun so well in Berlin. Wöhler's work on cyano compounds, beryllium, yttrium, and aluminum had already brought him fame; his synthesis of urea in 1828 was particularly dramatic, in its implications both for organic synthesis and organic isomerism. Wöhler's models were the sober empiricist Gmelin and the incomparable Berzelius; he was a superb and enormously prolific experimental chemist. Disinclined toward philosophy or even chemical theory, Wöhler fit in well with the rationalist and practical traditions of the Berlin Gewerbeschule and Kasseler Technische Hochschule and, later, the University of Göttingen. He impressed everyone with his kind and unassuming character. In their correspondence, he and Berzelius often ridiculed the Naturphilosophen and the Hegelian philosophers.^[14]

Wöhler first met Liebig in 1825, and the two young chemists always seemed to be stepping on each others' toes in their research during the middle to late 1820s. To avoid future problems, in 1829 they began to collaborate occasionally on topics of interest to both of them. By this time they were already close friends, and they maintained this friendship until Liebig's death in 1873. Wöhler learned from Liebig the newly improved method for elemental organic analysis one year after Liebig developed it in the fall of 1830.^[15] When Wöhler suffered the death of his young wife in 1832, Liebig invited him to Giessen for companionship and for the distraction from grief that hard work could offer.^[16] This was the period in which the two chemists completed their

work on the benzoyl series, an article that galvanized the chemical world and is usually regarded as the best single contribution of either Liebig or Wöhler.

In the spring of 1836, Wöhler transferred to Göttingen as Stromeyer's successor. Gmelin had declined the offer, and Wöhler, supported by Gmelin and Berzelius, was preferred over his close rival and friend Liebig. Liebig wrote Wöhler that he, like Gmelin, would have declined, but regretted that he did not get the offer to use to good effect with his administration.^[17] Stromeyer had inherited from J. F. Gmelin a small but well-equipped teaching and research laboratory on the ground floor of an old but spacious dwelling; a director's residence was provided upstairs. Shortly after his arrival, Wöhler wrote Berzelius describing many details, quite pleased with his new environs.^[18] He quickly became an ornament of the faculty and taught a phenomenal number of students during his forty-six year tenure there.

Since soon after his arrival in Göttingen Wöhler provided Kolbe with his first detailed introduction to chemistry, and since Wöhler's early teaching career has never been closely studied, a discussion of the latter is warranted. Every semester Wöhler taught general theoretical (inorganic) chemistry at 9:00 A.M. six days a week and a laboratory practicum every Monday, Tuesday, Thursday, and Friday at 11:00 to 1:00. In the summer semester he also taught pharmacy Monday through Friday at 6:00 A.M. Advanced students were allowed to work all day every day in the lab. He used the laboratory left him by Stromeyer, although he reappointed it in "Berzelian" style during his first semester and refloored and repainted it two years later. It appears that Wöhler had reasonable demand for his lectures and practicum during his first two years, but precise numbers and names are not available.^[19]

Whatever the initial numbers were, Wöhler's correspondence provides evidence for a noticeable increase in his enrollments beginning in summer semester 1838—coincidentally, the semester that Hermann Kolbe entered the university. Although exact information is sketchy here, too, we do know that he had twenty-eight students taking the practicum by the spring of 1840 and forty by the end of 1841, a remarkable level that continued to be maintained thereafter. After the influx started, it appears that Wöhler began to assign special projects to his most advanced students, investigations that might yield publishable results. There is no evidence that he ever did this in Berlin or Kassel, although it appears that he did have a practicum in Kassel.^[20] The first Wöhler pupils whose names appear as authors of published papers were pharmacy students: August Stürenburg and Friedrich Weppen, who enrolled at Göttingen in May 1838, and Georg

Schnedermann, who came in the fall of 1839. Apparently all were from bourgeois Hanoverian families. Schnedermann worked with Wöhler for no less than six years, published a number of short papers, and became Wöhler's assistant in his last semester. The first Wöhler chemistry Ph.D. was earned by Friedrich Carl Voelckel, the son of a Bavarian merchant, who enrolled for summer semester 1839 and received his degree three years later. He later became professor of chemistry in Solothurn, Switzerland.^[21]

In these early years, Wöhler's approach to publication of his student's work varied according to its significance and the student's precise role. He did not hesitate to use student results in his own papers, often without even naming the student, if the work was simply straightforward or mechanical assistance. If more skill or persistence had been needed, Wöhler was careful to acknowledge the assistance by name. Finally, there are a few examples in these years of Wöhler supervising what was essentially independent original research, and in such cases, the student published in his name alone.^[22]

From 1838 until 1841, Wöhler appears to have had only a very small number of these select advanced students working on such projects at any given time—one, two, or three per semester. By summer semester 1841—again, ironically, the very semester Kolbe became an all-day Praktikant—a real research cohort of eight advanced workers emerged for the first time. In addition to Kolbe, Voelckel, Schnedermann, and Weppen, the group included the medical students Otto Griepenkerl and August Vogel and the philosophy students August Beringer and Wilhelm Knop.^[23]

The pattern for the future was now set. Wöhler's increasing popularity and fame, and the rising profile of the chemistry profession itself, ensured that Wöhler would have substantial and rising enrollments ever after. Having inherited Stromeyer's assistant, H. A. Wiggers (later professor of pharmacology at Göttingen), Wöhler successfully petitioned for a second (Schnedermann), hired for the winter semester 1841/42, to help him with the now heavy numbers. That semester he had another increase, now past forty Praktikanten, more than the space could really accommodate. No fewer than fourteen of these men were doing advanced projects and working not just the scheduled four or eight hours per week but morning to evening in the lab. The number of these advanced Praktikanten, however, seems to have been rather variable, for in winter semester 1843/44 he had only three, while for each of the following two semesters the number jumped back up to twelve.^[24]

Some additional information on Wöhler's students can be obtained from careful study of the Göttingen matriculation registry. During the

period before Kolbe left Göttingen (fall 1842), a total of twenty-one students can be identified who were known (or can safely be presumed) to have studied with Wöhler. Eight listed chemistry as their field of study; the third of these was Kolbe. Kolbe's preparation apparently was not as thorough—or his progress not as swift—as that of Voelckel or Schnedermann, who arrived slightly later but were earlier in publishing articles from the lab. Nonetheless, it is interesting to note that Wöhler's most famous student was also very nearly his first. The rest of these twenty-one Wöhler students from Kolbe's days in Göttingen are divided by discipline roughly equally among pharmacy, medicine, and philosophy.^[25]

This cohort represents but a small fraction of the total number passing through Wöhler's lab during these years. The rest cannot be identified by name, but it is probable that they were mostly students of pharmacy or medicine. All told, the number of students who passed through his laboratory from his arrival in Göttingen until Kolbe left for Marburg six years later was probably between 100 and 200.

Early in the spring of 1842, ground was broken for a new laboratory extension in Hospitalstrasse, immediately adjacent to the old lab. Directed closely by Wöhler, construction of the "magnificent building" was completed by that fall; the two sections could now accommodate up to fifty workers.^[26] (This building, since destroyed, sufficed until 1859-1860, when a completely new and much larger laboratory was constructed for the Chemical Institute.) Unfortunately, Kolbe could not personally enjoy the expanded facilities since he left Göttingen in the fall of 1842. He must have watched with interest, however, as the facility slowly rose and became fitted for chemical research, while working daily in the old lab that summer.

Justus Liebig

Liebig (1803-1873)^[27] was the son of a wholesale materials supplier in Darmstadt. Like Wöhler and Berzelius, from an early age Liebig desperately wanted to be a chemist, and he was largely self-taught. In his autobiography, Liebig described his youthful passion for reading every chemistry book he could find and his utter devotion to reproducing every experiment possible in his father's makeshift laboratory—and moreover, to performing the same experiment many times until he had absolutely mastered it. He also got to know all the local artisans in tanning, dyeing, soapmaking, and metallurgy, and he thoroughly learned their empirical chemical arts. However, he was a poor pupil. When asked by his teacher what would become of him and he replied, "a chemist," both his classmates and the teacher exploded in laughter be-

cause, Liebig said, no one then considered chemistry as a possible career.^[28]

An unsuccessful pharmaceutical apprenticeship in Heppenheim (1817-1818) was followed by enrollment at the Universities of Bonn and Erlangen (1820-1822). Liebig was attracted by the lectures of Schelling and Kastner, the former of whom was the leader of Naturphilosophie and the latter reputed to be one of the best chemists in Germany. In 1821 he purchased and read an early (partial) German edition of Berzelius' textbook. At this point, he followed Kastner's advice to study for a time in Paris, and through Kastner's connections he was granted a stipend from the Grand Duke of Hesse-Darmstadt that enabled him to do so.^[29]

During his years in Paris (1822-1824) Liebig heard lectures by Arago, Dulong, Thenard, and Gay-Lussac, which had for him an "indescribable charm." Alexander von Humboldt, then residing in Paris, made the acquaintance of the young man and recommended him to Gay-Lussac, who took Liebig into his laboratory for collaborative research. The two men produced several important contributions—Liebig's first successful research. These events, as Liebig wrote in letters home and recollected in his memoirs of old age, came as revelations of a hitherto unknown world of true science. He was overwhelmed by the sophistication of the methods, the experimentalist commitment, and above all, the conscientious avoidance of unnecessary hypotheses. This was in marked contrast to the speculative approach of Schelling, L. Oken, G. H. Schubert, and other Naturphilosophen he had previously so admired in Germany. As Wöhler was forging a personal bond with Berzelius, Liebig was simultaneously becoming warm friends with Berzelius' principal French rival.^[30]

While still at Erlangen, Liebig had hoped eventually to gain a chair at a German university and, as Kastner had suggested to him, to open a laboratory-based pharmaceutical-chemical institute similar to existing models (especially that of J. B. Trommsdorff at Erfurt).^[31] This possibility was realized in the spring of 1824, when the Grand Duke (without consulting the faculty) offered Liebig an ausserordentlicher professorship at Hesse-Darmstadt's single (and tiny) university at Giessen. That fall, Liebig began his teaching career with twelve eager listeners and two Praktikanten in the university's improvised chemical laboratory, newly established in the guardroom of an abandoned army barracks at the edge of town. It appears that he shared this space, none too amicably, with the ordentlicher professor of chemistry, Ludwig Wilhelm Zimmermann (1782-1825). The following summer semester both men advertised chemistry courses, but only Liebig got customers. Despondent, Zimmermann committed suicide in the Lahn

River, and Liebig ascended to the rank of Ordinarius at the amazing age of twenty-two. He also was given a raise to the extremely poor annual salary of only 800 florins (equivalent to around $300 U.S. at the time) .^[32]

In the summer of 1826, Liebig, in conjunction with two colleagues, achieved his goal of opening a pharmaceutical-chemical institute. Since the university refused financial support for such a narrow professionalist endeavor, it was initially run as a private venture. They were allowed to use the university's chemical laboratory, however. Although the proprietors rated the institute's capacity as twenty to thirty students, it appears that in its first decade, usually only about ten worked there at any one time. Recent work suggests that the institute was initially successful in its advertised function of pharmaceutical training but not in its ultimate function of advanced chemical education and research.^[33] However, from winter semester 1826/27 on, Liebig insisted that all students in his chemical institute spend an entire semester working all day every day in the laboratory. Hence, his later claim that his pedagogical philosophy that later became so famous originated at the beginning of his Giessen years may well be accurate, in spirit if not in detail.^[34]

During the fall of 1830, Liebig invented an apparatus for elemental analysis that was to revolutionize organic chemistry—his Kaliapparat , or potash-bulb apparatus. Berzelius' third trip to Germany took place just at this time, and he was able to spend a few days with Liebig. Until this time, Berzelius had regarded Liebig as having been infected with the "geschwind aber schlecht" (fast but sloppy) methods of the French. Berzelius now changed his mind, and for the next decade, he and Liebig formed an extremely close bond.^[35] Liebig became an ardent Berzelian, but without yielding in his regard for Gay-Lussac. His friendships with Wöhler as well as Berzelius marked the time during which Liebig's loyalties were consolidated in the emerging German experimentalist school, of which he, Wöhler, and (slightly later) Bunsen were the most prominent members and of which Berzelius was the honorary dean. All of these men (with the possible exception of Bunsen) began to regard French chemistry of the new generation led by Dumas as sloppy, superficial, and self-aggrandizing.

By the early 1830s, Liebig had lost patience with his penurious administration, and he complained bitterly and tenaciously about the lack of financial and material resources in Giessen. Serious real and imagined illnesses added to the strain. Liebig's peremptory complaints, and even more so, his growing fame, made the administrators listen. In 1835 Liebig's laboratory institute was finally brought under the official aegis of the university, and funds were approved to renovate and ex-

pand it. Soon thereafter, Liebig himself received a substantial raise in salary, the laboratory was given a proper annual budget, and a new lecture hall was built. In 1838 the number of laboratory workers rose significantly—it reached twenty for the first time—and the composition of the practicum students shifted suddenly from nearly exclusively pharmacy to a mixture of pharmacy and chemistry majors. Within a few years they were nearly all chemists. Simultaneously, the lab began to attract foreign students. Liebig later suggested that the idea of practical chemical instruction "was at that time in the air," which constituted his explanation for the sudden popularity of his lab in the late 1830s.^[36]

Liebig's first students of note were Friedrich Knapp, who came to Giessen in 1835, and Heinrich Will and Hermann Fehling, who arrived in 1837. All three had successful academic careers in chemistry, Will becoming Liebig's successor. Up until then, only a handful of Ph.D. chemists had emerged from Liebig's laboratory; from this time on, large numbers of promising students were to come. This divide is also marked by a change in the sort of research projects that Liebig assigned. For years, Liebig had been using students to carry out analyses or isolated fragments of research in a similar way to what Wöhler did from about 1838. But for the first time in the late 1830s, we see Liebig organizing projects for multiple workers that were well articulated and coordinated around a single problem area of interest to Liebig. F. L. Holmes has plausibly suggested that this shift may have been related to a change in Liebig's own research orientation. From about 1836 Liebig became intensely involved in a variety of writing and editing projects, and in 1840 he gave up theoretical organic research entirely. As he began to find it difficult to maintain his personal research agenda, he began to trust that agenda more to his students.^[37]

He had more and more students to whom to turn. In 1839 Liebig's lab was again expanded and further renovated—the architect was J. P. Hofmann, whose son August Wilhelm entered Liebig's lab that same year—and his salary and budget were again increased. The renovation must have had something to do with a remarkable further increase in the quantity and quality of his students, traceable to that year. In addition to Hofmann, Hermann Kopp (already a Ph.D.) as well as Franz Varrentrapp, Lyon Playfair, and John Stenhouse all entered Liebig's lab that year, and Adolf Strecker came the next year. All became prominent academic chemists of the new generation. By 1841 Liebig had fifty workers, and in 1843 there were sixty-eight.^[38] In the latter year, a new branch laboratory for beginners was constructed to handle the crowds, which was physically separate from the old one, and it was placed under Will's directorship.^[39]

The great watershed in student demand for Liebig's lab was approximately simultaneous with that for the lab of his close friend Wöhler. The widespread assumption that Liebig must have enjoyed high popularity from the start appears not to survive careful scrutiny, for the transition to the pattern that became so famous, as we have seen, does not much predate 1840.^[40]

Robert Bunsen

Bunsen (1811-1899)^[41] was the son of a professor of modern languages at the University of Göttingen. He studied the sciences there, completing his Ph.D. under Stromeyer in 1831. From the beginning of 1832 to the fall of 1833, he traveled on a government grant in Germany, France, and Austria, seeking especially to investigate practical, technical, and geological subjects. A nine-month residence in Paris enabled him to learn from Gay-Lussac, Dumas, Chevreul, Pelouze, Regnault, and others, and he had the good fortune to spend a month in Giessen just when Wöhler and Liebig were collaborating on their benzoyl work. He also visited Mitscherlich and the Rose brothers in Berlin. On his return home, he habilitated at Göttingen, teaching technical chemistry and stoichiometry. Upon Stromeyer's death (18 August 1835) he took over the general lectures and the laboratory practicum. In the spring of 1836, he was appointed Wöhler's successor at the Kassel Technische Hochschule at the reduced salary of 650 thalers.^[42]

Even before his transfer to Kassel, Bunsen had begun to establish an enviable research reputation. His papers merited favorable mention in Berzelius' Jahresberichte from 1835 on, and that fall he had the pleasure of accompanying Berzelius on a journey from Kassel to Göttingen.^[43] From the late 1830s Berzelius began to extol Bunsen's work in the highest terms, both for its technical virtuosity and for its relevance to Berzelius' theoretical positions.^[44] Bunsen later described Berzelius as "my truest friend and counselor."^[45] To the extent that he had any theoretical commitment it was thoroughly Berzelian, maintaining the Swede's notational and formula styles to at least the 1880s, long after all others had abandoned it.^[46]

In Kassel, Bunsen Continued' to teach students in the small and primitive laboratory inherited from Wöhler and began what were to become world-famous researches into eudiometry and the cacodyl radical. His growing eminence led to his call in 1839 to the University of Marburg, initially as Extraordinarius (at 650 thalers) but raised to the Ordinarius rank (800 thalers) two years later. His predecessor, Ferdinand Wurzer, had since 1811 been teaching selected students in his laboratory, but had done so according to the older pedagogical pat-

tern, namely, on a small scale and on the basis of personal patronage. Wöhler, who spent a semester studying with Wurzer before transferring to Heidelberg, had found him intolerably old-fashioned.^[47]

By contrast, in the spring of 1840 Bunsen initiated a chemical practicum in the consciously "modern" (Liebig-Wöhler) style, namely, in the words of Christoph Meinel, a "planned, didactically self-contained, and consistently structured unit of instruction." Moreover, the practicum was publicly advertised in the university course list, and the professor took a standardized fee for it.^[48] The course was advertised as eight hours a week during precisely the same hours as Wöhler's practicum at Göttingen, but well-motivated students had no trouble persuading Bunsen to allow them to work all day every day. Bunsen was also careful to remit all fees for students who could not afford them—or even for those students who were exceptionally well motivated, regardless of their means.^[49] In 1852 he was called to Heidelberg as Leopold Gmelin's successor, and there he formed the nucleus of what was the liveliest academic chemical community—though not a "school" in the usual sense—in all of Germany until the 1860s.

Bunsen was a man of uncommon benevolence, kindness, and humor, universally admired by his peers and revered by his students. He had a straightforward practical and empirical orientation, was sensitive to technological implications of his work (without, on a point of principle, ever taking out a patent), and was uninterested in theory to a degree bordering on outright hostility. There is probably no great chemist in history who was more averse to hypotheses and theoretical structures of all kinds, nor one more skilled in laboratory operations. After his great cacodyl investigation, which ended in 1841, he never returned to organic chemistry; later in Heidelberg, he totally excluded this field from his activities. His students and biographers have plausibly suggested that his aversion to organic chemistry was directly related to his aversion to theory, for it was just at the time of his one and only sizable organic-chemical project that organic chemistry became and remained intensely theoretical—and correspondingly, intensely disputatious, a quality that was also anathema to the gentle Bunsen.^[50]

Another significant gap in Bunsen's career appears to have been directly related to his theoretical aversion: he never founded a school, despite his eminence and despite teaching a phenomenal number of students over no less than sixty-five years. Indeed, testimony from many sources agrees that he lavished his greatest attention on beginners and that once the tyro began to show initiative and independence, Bunsen lost interest in further guiding him. In Heidelberg, Privatdozenten were not directed or counseled by Bunsen, nor were they even allowed to work in his university facility. Instead, they were

forced to cobble together improvised labs in their lodgings or in specially rented spaces. This was due less to lack of consideration by Bunsen than to his adamant refusal to create a coherent chemical school. It was enough for him to continue to induct new members into the fraternity of academic chemists and to pursue his own always fruitful research agenda in physical, inorganic, analytical, and geological chemistry.^[51]