Parallel to the experiments for the 1908 publication on ammonia synthesis, Haber continued to work on the electric arc with Adolf König (Haber and König 1907d, 1908e). At the time, BASF was stagnant; its ability to innovate had become too dependent on external academic research (Stoltzenberg 1994, pp. 146–147), (Szöllösi-Janze 1998b, p. 171), (Abelshauser et al. 2004, pp. 142–146). In December of 1907, Carl Engler, a BASF Board member, brought the company into contact with Haber in an attempt to remedy the problem. In January 1908, Haber wrote to Engler, mainly to recount his experiments with König (he and others still considered the electric arc to be the most promising method of fixing nitrogen) (Haber 1908b):

I would like to respectfully point out that the fundamental factor moving me toward a relationship with industry is the need for apparatus and machines that are necessary for research on the problem and cannot be made available from public funds alone.Footnote 1

It was not only the electric arc experiments that Haber felt were ready for cooperation with industry. He and Le Rossignol, based on their latest experiments, now wanted to build an apparatus for the continuous production of ammonia from the elements which could be upscaled (Krassa 1966; Rossignol 1928). Haber had been reassured ammonia synthesis at high pressures was “a promising undertaking”Footnote 2 not only by his work with Le Rossignol, but also by two techniques that had recently come to his attention: the liquefaction of air at 200 atm as well as manufacturing methods in the formate industry (Haber 1908a), (Haber 1920, p. 337). An academic setting would no longer be adequate for research on either the electric arc or direct ammonia synthesis; further development would have to take place in tandem with industry (Jaenicke 1958b).

The cooperation between Haber and BASF and the industrial upscaling of ammonia synthesis from the elements are well documented and need not be repeated here (Schwarte 1920, chapter 4), (Mittasch 1951, pp. 90–142), (Holdermann 1960, pp. 65–121), (Haber 1971, chapter 4), (von Nagel 1991, pp. 16–50), (Reinhardt 1993), (Stoltzenberg 1994, chapter 5), (Szöllösi-Janze 1998b, chapter 4), (Abelshauser et al. 2004, pp. 142–146), (Sheppard 2020, chapters 7 and 8). However, several points are pertinent to the scientific perspective (Fig. 12.2).

Haber and BASF entered into two contractual agreements on March 6, 1908 (Fig. 12.1). One was with Haber and König for the development of the electric arc process and the other was with Haber for the development of direct ammonia synthesis from the elements. BASF was still investigating the cyanamide process and it was only at the end of 1908 that their attention turned from this process and the electric arc to Haber’s ammonia synthesis (BASF 1908b,c), (Mittasch 1951, p. 90). Throughout the first half of 1909, work continued on the design and construction of an apparatus that was not only capable of continuously producing ammonia at high pressures, but also exploited a heat exchange system. A wide array of catalysts, including iron, nickel, chromium, manganese, uranium, and osmium was also tested. On July 2, 1909, Haber and Le Rossignol were ready to present the result and invited Carl Bosch, Alwin Mittasch and Julius Kranz (chief mechanic at BASF) to Karlsruhe for the demonstration (Fig. 12.1). It turned out to be a dramatic finish. A problem with a bolt during the initial assembly meant that the apparatus could not be put under pressure. The repairs took so long that Bosch eventually left; he did not see the historical presentation that followed. But Mittasch and Kranz were there to witness it and after the necessary repairs had been made the machine was turned on. At first nothing appeared to happen–but then the drops of liquid began to appear. Haber took a sample and demonstrated to the representatives from BASF: it was ammonia. He and Le Rossignol used uranium and osmiumFootnote 3 catalysts and produced ammonia continuously for several hours between 600–900∘C at a pressure of ∼175 atm (Haber 1909b), (Mittasch 1951, p. 77), (Sheppard 2020, chapter 8). It was here that all the elements in Ostwald’s “recipe” from his 1900 patent application, established on the basis of physical chemistry, were brought together in one working system. It was a technological success and formed the basis for BASF’s prosperity in the nitrogen market.Footnote 4

Fig. 12.1
figure 1

Haber and Le Rossignol’s laboratory apparatus for the continuous production of ammonia. Source: Archive of the Max Planck Society, Berlin-Dahlem, Jaenicke Sammlung, Picture Number XII.2/7

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Fig. 12.2
figure 2

Fritz Haber in conversation with Heinrich von Brunck of BASF in 1908. By David Vandermeulen from Fritz Haber: Les Héros (Vandermeulen 2007); ⒸDavid Vandermeulen/Guy Delcourt Productions

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Money would also complicate the arrangement as it had done in 1904 (Reinhardt 1993, 299–301), (Stoltzenberg 1994, pp. 144–151, 179–180), (Szöllösi-Janze 1998b, pp. 172–175, 180, 189–191, 481–487). Through a series of contracts and agreements, Haber and BASF arranged funding for equipment and compensation for his assistants and for Haber himself. For nitrate production, BASF agreed to pay 10,000 marks after the Haber-König patent was issued and 6,000 marks per year for further work. In addition, the company would finance equipment for three years and 10% of net profits would go to the inventors for the life of the patent. The agreement was soon renegotiated and by the end of 1908, Haber agreed to 23,000 marks per year for 10 years for ongoing research. For work on direct synthesis from the elements, Haber received a flat sum of 8000 marks in addition to the 10% stake. Haber made a further agreement with Le Rossignol that the engineer would receive 40% of profits from any future technical applications. By the time Haber and Le Rossignol demonstrated their apparatus in Karlsruhe in 1909, the ammonia “account” was 4400 marks overdrawn, and Haber requested an additional 8000 for catalyst research. BASF granted the entire sum. Due to substantial changes in the preferred method for fixed nitrogen production as well Haber’s appointment as director to the Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry, a new agreement went into effect on November 1, 1911 in which Haber would receive 10,000 Marks per year for his services.

When ammonia production began at Oppau in 1913, the 10% stake in production became the subject of debate. While Haber understood it to be 10% of net profits, BASF insisted that it meant 10% of the difference between their profits from the Haber-Bosch-Process and what they would have earned had they continued other methods of ammonia production (the multi-step process). In consideration of production costs and sales prices at the time, this meant Haber would receive only two pfennigs per kilogram ammonia instead of five. He claimed that BASF had not properly informed him of this disparity during contract negotiations, but ultimately he was able to reach a compromise with the company. He would receive a flat sum of 1 to 1.5 cents per kilogram ammonia, depending whether it was produced directly by BASF or under license, with which he hoped to secure a growing percentage as production prices dropped. In 1919, the rate was lowered to 0.8 pfennigs per kilogram, with compensation to come at a later date (post-war circumstances caused Haber to fear accusations of war crimes which could result in the seizure of his assets (see Part I, Chap. 8)). Payments continued into the 1920s and amounted to several million marks. It was only ten years later, during the period of hyperinflation, that the agreement was no longer advantageous to Haber. In the end, an arrangement was reached in 1923 in which Haber likely received a one-time compensation in addition to the per-kilo share (now worth essentially nothing). The size of the sum is not known, but it seems to have been appropriate. In addition, Haber was offered a position on BASF’s board of directors for which he received remuneration.

Diverging economic and academic aspirations also affected the dynamic between Haber and BASF when it came to the dissemination of scientific knowledge. The contractual negotiations between Haber and BASF included the publication of Haber’s laboratory results and future disclosure of progress made while working with BASF. Haber had requested that any such arrangement be left out of the contract and that he and BASF discuss publication on a case-by-case basis; Haber felt he needed to accept some form of agreement in this respect, although it went against his conviction as a scientist (Engler et al. 1909; Haber 1909a). BASF agreed to Haber’s initial request because the paper, according to an internal memo from August Bernthsen, a member of the board of directors at BASF, was “mainly of a polemic nature…that should serve to demonstrate that [Haber] is correct in the face of the attacks by Professor Nernst.”Footnote 5 Haber acted quickly to publish in 1908 (BASF 1908a; Haber 1908c; Haber and Rossignol 1908f). However, BASF later became stricter in an attempt to guard both the progress made during the later stages of technological development and pending patent applications (Stoltzenberg 1994, pp. 165–168), (Szöllösi-Janze 1998b, pp. 181–183). Confidentiality was of even greater concern after Mittasch demonstrated in January 1910 that his composite catalyst produced results comparable with osmium and overcame a critical hurdle toward industrialization (Mittasch 1951, pp. 91–121), (BASF 1910a,d). As a result, the last report by Haber and Le Rossignol on the subject of ammonia synthesis from the elements was prepared in 1909 but did not appear until 1913 (Haber 1909c; Haber and Rossignol 1913b).

Haber wanted to publish his results to defend himself against Nernst’s comments, which had continued in literature into 1910 (Haber 1909e, 1910d; Nernst 1910). But he also wanted to publicize his own success as a scientist. In January, he requested permission from BASF to publish his results on ammonia synthesis as a lecture, just as he had done for the results on the electric arc (Haber 1910a,d,h). It was important to Haber to introduce the public to the ammonia synthesis process as a whole. Other factors, even details of the catalysts, were of secondary importance because negotiations with BASF over the release of such details would be a lengthy process. Haber also argued it would benefit the patent process (Haber 1910f). Although Bernthsen was wary of losing the edge BASF had on the competition as well as possible adverse effects on the patent applications, he finally agreed to the publication of a shortened overview (BASF 1910h,k).

The negotiations on a final agreement, however, lasted through February and did not proceed without pressure from Haber. One of his initial drafts was too detailed for BASF; they preferred he focus on the general fact that “the technical synthesis of ammonia from the elements, which heretofore had been assumed hopeless…has succeeded…”Footnote 6 Haber acquiesced at first, asking only for permission to send his detailed account to the Academy of Sciences in Vienna for later publication and, presumably, to secure his claim to the results (BASF 1910k; Haber 1910b). But in January of the following year, he notified the Zeitschrift für Elektrochemie of his lecture and planned a date with Carl Engler in Karlsruhe. Three weeks before the scheduled date, Haber had still not received permission from BASF. The two parties finally agreed on the content of Haber’s lecture only days before he was due to speak (BASF 1910b,c,e,j; Haber 1910c,e,g,j). Haber held the lecture on March 18, 1910 in front of the Scientific Society of Karlsruhe.Footnote 7 BASF was still uncomfortable printing all the information Haber had presented at the lecture and insisted on an abridged published version. Haber framed his discovery within the context of agriculture and the explosives industry before focussing on the use of unusually high pressures and an osmium catalyst. “Through this result,” he wrote, “the basis for an industry of synthetic ammonia is secured.”Footnote 8 The iron and alumina catalyst received no mention (BASF 1910f; Haber 1910l,m), but the lecture and the publication produced the publicity Haber wanted. The event was covered in local newspapers, trade journals and commentaries, and Haber was contacted by members of academia, industry, and other personalities. The attention caught BASF off guard (BASF 1910g).Footnote 9

In the context of Haber’s success at BASF, it is also informative to consider Nernst’s publication on the specific heat and equilibrium of ammonia from February of 1910 (Nernst 1910). In it, Nernst introduced new evaluations of the thermal characteristics of ammonia and vehemently defended Jost’s 1908 results and their agreement with his 1906 heat theorem. The final page of the six-page publication was primarily devoted to the “polemic” with Haber, which Nernst blamed mainly on his peer. Nernst’s tone in the description of the interaction, indeed his rehashing of the entire chronology on a scientifically factual, but also dramatic basis, shows the effect the episode had on him. It is also clear Nernst still viewed ammonia equilibrium as an important intersection between experiment and theory: it would aid in the verification of his heat theorem, which ultimately became a lengthy process (Nernst 1921, p. 359). Haber, on the other hand, discussed Nernst in private communication but not in his latest publication, the printed version of his 1910 lecture (Haber 1909e, 1910e,f). To some extent, Haber had moved on. Developments at BASF continued with Carl Bosch and Alwin Mittasch’s successful conversion of Haber’s apparatus into an industrial process; Haber himself already viewed the fixed nitrogen industry as secure, and his work in the field was coming to an end. Before the First World War, he oversaw further laboratory measurements for the ammonia system, experiments that increasingly tended toward basic research, but was less involved in Bosch and Mittasch’s continuing work at BASF because of his confidence in the company and the abilities of its employees (Haber 1914a). In 1911, Haber became director of the KWI for Physical Chemistry and Electrochemistry in Berlin where he turned to other fields of research, including radiation, electron dynamics, and his old passion for the electric arc (Fig. 12.3). He would not return to the subject of ammonia synthesis (Haber 1911), (Coates 1937, pp. 1664–1670), (Mittasch 1951, p. 80), (Burchardt 1975, pp. 98–100), (Johnson 1990, chapter 7), (Stoltzenberg 1994, p. 170), (Szöllösi-Janze 1998b, p. 180), (Steinhauser et al. 2011, pp. 10–25).

Fig. 12.3
figure 3

Berlin at the time Haber was being considered as director of the KWI for Physical Chemistry and Electrochemistry. By David Vandermeulen from Fritz Haber: Les Héros (Vandermeulen 2007); Ⓒ David Vandermeulen/Guy Delcourt Productions

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Haber and Nernst were not diametrically opposed to one another’s viewpoints, despite sometimes having different notions of what it meant to arrive at the correct solution. Nernst focused on scientific foundations, whereas Haber prioritized application and industry. Haber believed the end result was the description of a process that could be industrially upscaled; Nernst thought it to be agreement between experiment and theory (though he was also drawn to industrial implementation). However, they must have seen eye to eye on some things: Nernst supported Haber and BASF in their 1910 patent disputes on ammonia synthesis against industry competitors (Suhling 1972), (Stoltzenberg 1994, pp. 170–180), (Szöllösi-Janze 1998b, pp. 181–185), and Nernst helped convince Haber to accept the position of director of the KWI (Haber 1910k), (Stoltzenberg 1994, p. 206), (Szöllösi-Janze 1998b, p. 222).

“I have always strived toward the truth,”Footnote 10 Nernst is quoted as having said near the end of his life (Haberditzl 1960), (Bartel 1989, p. 109). These words, taken with a grain of salt, describe Nernst’s approach to ammonia, just as it does Haber’s.

Perhaps this unique intersection of ideas is what made them such productive rivals.

As for the emergence of Haber and Le Rossignol’s detailed results on ammonia synthesis from the elements, their final report, “Über die technische Darstellung von Ammoniak aus den Elementen” (On the technical production of ammonia from the elements), was published in 1913 along with a report of a lecture Haber held at the Meeting of the German Chemical Society after BASF’s patents were granted and construction of the plant at Oppau was in an advanced stage (Haber 1913a; Haber and Rossignol 1913b).Footnote 11 The next year, another short article appeared along with an extensive set of reports documenting refinements as well as new measurements carried out in Karlsruhe and Berlin, and, yes, in which the debate with Nernst continued (Haber 1914b,c; Haber and Greenwood 1915a; Haber and Maschke 1915b; Haber and Tamaru 1915c,d; Haber et al. 1915e,f). By then, the Haber-Bosch plants at Oppau and Leuna were in operation and poised to upend the world’s nitrogen market, revolutionizing how humans produce nourishment and lead their lives. There was, however, still much to be understood from the scientific perspective.