We have followed the scientific developments of ammonia synthesis from the elements from the initial determinations of equilibrium through to the beginning of industrial upscaling during the first decade of the twentieth century. A central result of this presentation is that natural scientific details about the involved chemistry and physics could be accurately presented. Not only does the combination of scientific and historical context to Haber’s work clear up misunderstandings about the scientific developments and Haber’s interaction with Nernst, it also allows us to understand why Fritz Haber took on the challenge of ammonia synthesis in the first place (Chap. 10). His attraction stemmed largely from his interest in fundamental principles, although he was not as preoccupied with this aspect as Nernst. Haber’s enthusiasm should not, however, be completely decoupled from possible industrialization of new technology, financial gain, or the need for the production of raw materials for fertilizer and explosives. The set of circumstances as well as the scientific arena in which he acted was complex and improbable. It reminds us of the reality of scientific discovery: the time must be right, and even then, biases or preconceived notions can impede progress (Haber 1920, p. 326), (Kuhn 1959). But the obstacles are only temporary.

The central historical contribution (and the most tangible example for the progress of science) was the “interaction” or “exchange” between Haber and Nernst, a dynamic which extended beyond the meeting of the Bunsen Society in Hamburg in 1907. Nernst, whether consciously or not, incited Haber to further his work on ammonia on three distinct occasions apart from the involved and sustained public debate in literature: the letter in 1906, the Bunsen Society meeting in 1907, and the meeting in 1908 in Berlin where Haber learned of Nernst’s relationship with Griesheim-Elektron. The development displays many random events with respect to future outcomes. In retrospect, however, it is clear how a basis in fundamental physical principles and mathematics leads to success. Context for their exchange was also provided by Haber’s and Nernst’s individual approaches. Haber and his team learned the importance of the verification of theory through experiment while Nernst and his co-workers understood the power of experimental results to determine something which could not be described by theory: the behavior and efficacy of a real-life catalyst. Haber and Nernst’s interaction provided a fact-based, alternative objective (scientific progress) when it appeared physicochemical realities may not allow an industrial upscaling. Money and recognition also played their part. While the meeting of the Bunsen Society may have been the apex of the exchange with its element of drama, their ongoing relationship as a whole must be considered the important factor in the successful conclusion to ammonia synthesis from the elements.

It is important to reiterate that at some point after the Bunsen Society meeting, Haber’s sense of certainty toward his own results crystallized, despite Nernst’s continued commentary. Lawrence Holmes wrote (in reference to Lavoisier but still fitting here) that a development like Haber’s toward increased confidence is a consequence of the “conditioning effect of the passage of time […] At some point…a scientist must make the decision to commit himself personally to what he has come to believe, even though he has not resolved all of his own doubts, and can never be certain he is right (Holmes 1985, p. 107).”

Further considering the developments after the events in Hamburg, Friedrich Jost’s own theoretical and experimental abilities became apparent through his independent publications. It was not only Haber and Nernst who were able to produce these studies. In consideration of the assistants and technicians van Oordt, Le Rossignol, Kirchenbauer, Jost and Jellinek, the base of individuals who contributed to the scientific breakthrough broadens and moves us away from the single story of one courageous scientist devoting himself over years to the advancement of a narrow sliver of knowledge. In fact, Haber’s story alone challenges this stereotype: he actively helped his assistants Heinrich Danneel, Friedrich Kirchenbauer, Gerhardt Just, Adolf König, and Robert Le Rossignol navigate the academic world and was consistent in recognizing and publicizing the contributions of others, including the Margulies brothers (BASF 1910i; Haber 1909d, 1910i; Krassa 1955). He cared deeply about research and education and was known for his fervent scientific discussions with colleagues and students (Engler et al. 1909; König 1954; Krassa 1955; Schlenk 1934), (Sheppard 2020, p. 53) (Fig. 14.1). Even politically, Haber showed deftness in his position at the university, in his negotiations with BASF, in the establishment of the Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry, and in his relationship with Nernst. He was not a one dimensional man fixated on a singular scientific goal, but exhibited growing variety in his academic roles as professor, researcher, and mentor.Footnote 1 Nernst (and Ostwald) exhibited similar traits with their students and in their careers (Bartel 1989, pp. 34, 51). Perhaps a more accurate, albeit unwieldy name to consider is the Haber-Bosch-Mittasch-Nernst-Ostwald-Le Rossignol-van Oordt -Kirchenbauer-Jost-Jellinek-Process.

Fig. 14.1
figure 1

“Parody Photo: The Colloquium.” At the Institute for Physical Chemistry and Electrochemistry, Technical University of Karlsruhe in 1909. There are many indications that Haber’s staff was not “all work and no play.” Source: Archive of the Max Planck Society, Berlin-Dahlem, Jaenicke and Krassa Collections, Picture Number VII/5

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While my study of the history of ammonia synthesis has brought me to these particular conclusions, it has also left a central question unanswered: why was Haber at times aloof, or even dispassionate toward the nitrogen-hydrogen-ammonia system during the years he was intensely occupied with it? It began with the matter-of-fact way he and van Oordt presented their strikingly accurate 1905 results in a field where so many had tried and failed before them. What they had achieved was momentous and symbolic, but Haber initially made little of it, perhaps because industrialization appeared unlikely. Furthermore, it is puzzling why Haber never discussed the scientific side of ammonia synthesis in his correspondence. He discussed an array of other topics in detail and with obvious fervor. Did such letters simply not survive? Or did the certainty he had in the accuracy of his measurements render such discussion superfluous? This interpretation fits well with the increasingly confident tone found in his publications and, as I put forward in Chap. 10 in consideration of his wider scientific interests, that he saw ammonia mainly as a vehicle to apply and complement the theory he had already developed. The first set of measurements from 1905 accomplished this goal and perhaps there was nothing more he wished to achieve. Despite Haber’s tendency in Karlsruhe to move toward more fundamental problems, in the case of ammonia synthesis he never seemed to reach Nernst’s level of contemplation with regards to the basic physical mechanisms behind the chemical dynamics. This circumstance would also help explain why he never returned to the subject after the upscaling at BASF. In a nutshell, it is not clear what exactly Haber’s intention was after he published his initial 1905 results with van Oordt and his scientific goals had apparently been reached. It was more than money or reputation and may have changed over time. Perhaps the fact that Chap. 10 contains such a wide array of factors explains the ambiguity.

Whatever the reason, it is curious that the (arguably) most important piece of research of Haber’s career occupied him in a such narrow manner, both in terms of time and intellectual curiosity.

Returning to the concept of The Haze, the objective of Part II was also to show, beyond a discussion of the scientific details, that the arena in which discovery takes place is complex and includes any number of elements. While this characteristic is often postulated, here we can discuss concrete causes. In the introduction to Part I, I alluded to the theoretically unlimited set of influential factors that renders this concept of little practical value. Rather, it is useful to consider how this complexity has been illuminated. What are the key components that forged it and how are they interlocked? The historical run-up to 1903 described in Part I also possesses a convoluted dynamic that will result in a mature scientific arena at an uncertain point in time, under uncertain circumstances. Again, the time must be right. However, the events of Part I may be the more simple set of complexities. Once the stage has been set for a Fritz Haber, a Walther Nernst, and their assistants, the “microcomplexities” within the mature arena begin to emerge (Kanter 1988; Sgourev 2015). In the case of ammonia, the complexities were increased by Haber’s and Nernst’s unique backgrounds suspended between experiment, theory, and industry, the technical prowess of the assistants within the context of the then-technically achievable, outside financial incentive provided by industry, political, and societal pressures, the state of theoretical knowledge, and efficacy of applicable approximations. Different forms of knowledge exchange along with political wrangling contributed to the evolution within this setting. Considering these intricacies, the reasons for the complexity is no longer a surprise. Increased attention to local, national, or global circumstances, movements of knowledge, or the effects of the academic setting could extend the detail even further (Renn 2012; Wendt 2016).

We may also consider the resolution of the problem. The mystery of ammonia synthesis has been solved; we have been able to synthetically produce the chemical for over a century. But are we, after having reviewed the subordinate “microcomplexities” in this section, able to clearly identify the scientific breakthrough? Was it Haber’s initial 1905 measurements? They were precise enough to form the basis of further scientific and industrial advancements. Was it one of the subsequent publications with increased accuracy or knowledge of improved technical possibilities (i.e. higher working pressures)? Or the Bunsen Society meeting in Hamburg? Or was it later at Haber and Le Rossignol’s 1909 demonstration in which all of the elements needed for industrial synthesis were first brought together?Footnote 2 Perhaps it was in 1910, when Haber gave his lecture in front of the Scientific Society of Karlsruhe and made the breakthrough public for the first time. Or was it a combination of all these, extended in time?

The answer may hinge on our perspective or how we frame the question and depends on our definition of the terms “breakthrough” or “discovery.” Are the meanings of these words concrete enough that we truly understand each other when we use them? If not, we may need a finer nomenclature to better characterize the progression of science. Such an improvement would certainly aid in understanding the dynamic of the Haze.