Fritz Haber

• 1. Introduction

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  Fritz Haber, the German chemist born in 1868, devised a method that now underpins roughly a third of the world's annual food production. The method turns nitrogen gas and hydrogen gas into ammonia, the raw material for both fertilizers and explosives. Historians have called him one of the most important industrial chemists in human history. The same man is also remembered by a darker title: the father of chemical warfare. How did one chemist end up carrying both reputations? What did that work cost the people closest to him? And what became of a man who gave so much to a country that later turned on him?

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• 2. A Merchant's Son

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  On the 9th of December 1868, Fritz Jakob Haber was born in Breslau, in the Kingdom of Prussia, now the Polish city of Wrocław. His family was well off and Jewish. Its roots reached back to a great-grandfather, Pinkus Selig Haber, a wool dealer from Kempen, now Kępno. A Prussian edict of the 13th of March 1812 had decreed that Jews like Pinkus were "to be treated as local citizens and citizens of Prussia". Under such rules, the Habers rose into respected positions in business, politics, and law.

  His parents, Siegfried and Paula Haber, were first cousins who married despite considerable opposition from their families. Siegfried was a well-known merchant who had founded his own firm in dye pigments, paints, and pharmaceuticals. Paula had a difficult pregnancy and died three weeks after Fritz was born. Siegfried was devastated, and the baby was left in the care of various aunts. When Fritz was about six, his father married Hedwig Hamburger, and the couple had three daughters named Else, Helene, and Frieda. Siegfried never fully accepted his son, whom he linked to Paula's death. Fritz still grew close to his stepmother and his half-sisters.

  At the Johanneum School, Haber sat among Catholic, Protestant, and Jewish pupils, because it was a "simultaneous school" open equally to all three. At age 11 he moved to the classical school in Breslau, in a class divided evenly between Protestant and Jewish students. His family supported the Jewish community and kept many traditions, but stayed distant from the synagogue. Haber identified strongly as German and less so as Jewish.

  In September 1886, Haber passed his examinations at the St Elizabeth gymnasium. His father wanted him to apprentice in the dye company. Haber won permission instead to study chemistry in Berlin under A. W. Hofmann, director of the Institute for Chemistry. The first winter semester, in 1886-87, disappointed him. For the summer semester of 1887 he went to Heidelberg University to study under Robert Bunsen. He then returned to Berlin and enrolled at the Technische Hochschule in Charlottenburg.

  In the summer of 1889, Haber was conscripted and left university for a year of volunteer service in the Sixth Field Artillery Regiment. Afterward he returned to Charlottenburg and became a student of Carl Liebermann. He also attended Otto Witt's lectures on the chemical technology of dyes. Liebermann assigned him reactions with piperonal, and the thesis appeared in 1891 as Ueber einige Derivate des Piperonals. Charlottenburg could not yet grant doctorates, so examiners from the University of Berlin judged his work. He earned his doctorate cum laude in May 1891.

  Back in Breslau, Haber found that his father's business did not suit him. Through Siegfried's connections he completed apprenticeships at Grünwald and Company, a Budapest distillery, then at an Austrian ammonia-sodium factory, then at the Feldmühle paper and cellulose works. These stints convinced him to learn more about technical processes. He persuaded his father to let him spend a semester in Zürich with Georg Lunge at the Polytechnic College. In the Fall of 1892 he returned to Breslau once more, and father and son kept clashing.

  Siegfried, despite his son's doctorate, made him take handwriting courses and work as a salesman. Haber urged a switch from natural to synthetic dyes, and his father refused. Siegfried later followed global trends and switched anyway. Then a cholera epidemic arrived, and Haber advised buying calcium hypochlorite, the only known preventive at the time. The epidemic stayed local, and the firm was left holding a large stock of an unstable chemical. Siegfried told his son to go back to his studies, since he did not belong in business. It was the clearest sign yet that Haber's future lay in a laboratory.

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• 3. Karlsruhe Years

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  Ludwig Knorr employed Haber as an independent assistant at the University of Jena from 1892 to 1894. During that time Haber converted from Judaism to Lutheranism, possibly hoping to improve his chances of a better academic or military position. Knorr recommended him to Carl Engler, a Karlsruhe professor fascinated by the dye industry and by synthetic materials for textiles. Engler referred him to a colleague, Hans Bunte, who made Haber an Assistent in 1894.

  Bunte suggested that Haber study how hydrocarbons decompose under heat. Careful quantitative analysis led to a classic result: "the thermal stability of the carbon-carbon bond is greater than that of the carbon-hydrogen bond in aromatic compounds and smaller in aliphatic compounds". The work became his habilitation thesis. Haber then took the post of Privatdozent in Bunte's institute, teaching dye technology and continuing his study of burning gases.

  In 1896 the university supported a trip for Haber through Silesia, Saxony, and Austria to learn about advances in dye technology. A similar journey in 1897 focused on electrochemistry, a subject he had explored with fellow privatdozent Hans Luggin. His 1898 book, Grundriss der technischen Elektrochemie auf theoretischer Grundlage, drew considerable attention, especially for its treatment of the reduction of nitrobenzene. In the foreword he thanked Luggin, who died on the 5th of December 1899. Another collaborator was Georg Bredig, a student and later an assistant of Wilhelm Ostwald in Leipzig.

  On the 6th of December 1898, with backing from Bunte and Engler, Haber received the title of Extraordinarius and an associate professorship. The order came from the Grand Duke Friedrich von Baden. At Karlsruhe he worked across many fields. With Friedrich Bran, he explained theoretically steps in textile printing processes developed by Adolf Holz. Discussions with Engler led him to describe autoxidation in electrochemical terms, separating dry from wet autoxidation. His thermodynamic studies of reactions in solids confirmed that Faraday's laws hold for the electrolysis of crystalline salts. That finding gave a theoretical basis for the glass electrode and for measuring electrolytic potentials.

  Haber's studies of irreversible and reversible electrochemical reduction are regarded as classics. He also examined the passivity of non-rare metals and the effect of electric current on metal corrosion. His second book, Thermodynamik technischer Gasreaktionen, appeared in 1905 and in translation in 1908. It was later called "a model of accuracy and critical insight". Together with Max Born, he also proposed the Born-Haber cycle, a way to evaluate the lattice energy of an ionic solid.

  In 1906, Max Le Blanc, chair of physical chemistry at Karlsruhe, left for the University of Leipzig. After a search committee made its recommendations, the Ministry of Education in Baden offered the full professorship in physical chemistry to Haber. He accepted, and the laboratory he inherited would soon host the experiments that made his name.

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• 4. Ammonia From Air

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  In 1909, Haber became the first chemist to make ammonia by synthetic means. Chemists had pursued the goal ardently and failed because the reaction demands so much energy. Haber combined nitrogen and hydrogen at 500 degrees Celsius, about 932 degrees Fahrenheit, and a pressure of 2900 psi, with a catalyst present. This first success was at laboratory scale. His assistant, Robert Le Rossignol, worked with him on the invention at Karlsruhe.

  Le Châtelier's principle, announced in 1884, says that a system in equilibrium responds to a change by minimizing the effect of that change. Chemists already knew that a nickel-based catalyst could decompose ammonia. From the principle, they could infer that the reaction might be reversed at high temperature and pressure. There was a catch. The equilibrium actually improves at low temperatures, which is why a catalyst became necessary, since hot ammonia breaks back into its elements.

  To reach commercial quantities, Haber turned to industry and partnered with Carl Bosch at BASF. Bosch, a German chemist focused on pressure chemistry, scaled production up to industrial levels in 1913. The result is now called the Haber-Bosch process, and it grew more efficient as new methods were found. A more refined iron catalyst replaced the uranium or osmium catalysts used before. Lowering the temperature while raising the pressure increased the rate at which ammonia formed.

  Before this, nitrogen-based products such as fertilizer depended on ammonia from limited natural deposits. Now atmospheric nitrogen offered an easily available and abundant base. Synthetic fertilizers could be mass produced, and farmers could grow more food on the same land in the same time. Population could then grow at speeds that history had never sustained.

  Chile had been a major and almost unique exporter of natural nitrate deposits such as sodium nitrate, known as caliche. After the Haber process arrived, Chilean output fell from 2.5 million tons in 1925 to just 800,000 tons in 1934. In 1925 it employed 60,000 workers and sold at US$45 a ton. By 1934 it employed 14,133 workers and sold at $19 a ton. Today the world produces more than 100 million tons of synthetic nitrogen fertilizer each year.

  Fertilizer that washes into rivers and lakes leaves a lasting mark on the surrounding area. The nitrogen-rich water invites algae blooms. The algae remove oxygen from the water and create zones with none at all, which harms the local fauna.

  Haber was awarded the 1918 Nobel Prize in Chemistry, though he actually received it in 1919. In 1918 he also shared the Bunsen Medal of the Bunsen Society of Berlin with Carl Bosch. In his Nobel acceptance speech he said: "It may be that this solution is not the final one. Nitrogen bacteria teach us that Nature, with her sophisticated forms of the chemistry of living matter, still understands and utilizes methods which we do not as yet know how to imitate."

  From 1911 to 1933, a large part of Haber's work took place at the Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry in Berlin-Dahlem. His research there reached into combustion reactions, adsorption effects, electrochemistry, and free radicals. Haber is sometimes wrongly credited with first synthesizing MDMA. That honor belongs to Anton Köllisch, a chemist at Merck KGaA, who made it in 1912.

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• 5. Chlorine at Ypres

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  In October 1914, Haber joined 92 other German intellectuals in signing the Manifesto of the Ninety-Three. The proclamation galvanized support for the war in German schools and universities. Haber greeted the war with enthusiasm. Soon after it began he was promoted to captain and made head of the Chemistry Section in the Ministry of War. The Kaiser gave him the rank that Haber had been denied 25 years earlier, during his compulsory service.

  The Hague Convention of 1907, which Germany had signed, forbade chemical weapons in shells. Haber nonetheless played a major role in the non-ballistic use of chemical warfare. He led teams developing chlorine gas and other deadly gases for the trenches. He first proposed using heavier-than-air chlorine to break the trench deadlock during the Second Battle of Ypres. The team he assembled held more than 150 scientists and 1,300 technical personnel.

  Pioneer Regiments 35 and 36 formed a special gas troop under Otto Peterson, with Haber and Friedrich Kerschbaum as advisors. Haber actively recruited physicists, chemists, and other scientists into the unit. Future Nobel laureates James Franck, Gustav Hertz, and Otto Hahn served as gas troops under him. In 1914 and 1915, before Ypres, his unit investigated reports that the French had used Turpinite, a supposed chemical weapon, against German soldiers.

  Haber was on hand personally when the German military first released chlorine at the Second Battle of Ypres in Belgium. The battle ran from the 22nd of April to the 25th of May 1915. He also helped develop gas masks with adsorbent filters that could protect against such weapons. Gas warfare became, in a sense, the war of the chemists, with Haber pitted against the French Nobel laureate chemist Victor Grignard.

  While studying the effects of poison gas, Haber noticed that a long exposure to a low concentration often had the same deadly effect as a short exposure to a high one. He formulated a simple mathematical relationship between gas concentration and the necessary exposure time. It became known as Haber's rule.

  Haber once said: "during peace time a scientist belongs to the world, but during war time he belongs to his country". He answered charges of inhumanity by arguing that death was death, by whatever means it was inflicted. He appealed to history: "The disapproval that the knight had for the man with the firearm is repeated in the soldier who shoots with steel bullets towards the man who confronts him with chemical weapons. … The gas weapons are not at all more cruel than the flying iron pieces; on the contrary, the fraction of fatal gas diseases is comparatively smaller, the mutilations are missing".

  Albert Einstein was among the sharpest contemporary critics of Haber's chemical weapons work, and modern scientists have criticized it too. Haber, a patriotic German, remained proud of his service and was decorated for it. Within days of Ypres, a tragedy would unfold in his own garden.

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• 6. Clara and Family

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  Haber met Clara Immerwahr in Breslau in 1889, during his required year of military service. Clara was the daughter of a chemist who owned a sugar factory, and she was the first woman to earn a PhD in chemistry at the University of Breslau. She converted from Judaism to Christianity in 1897, several years before she and Haber became engaged. They married on the 3rd of August 1901, and their son Hermann was born on the 1st of June 1902.

  Clara was a women's rights activist and, by some accounts, a pacifist. Intelligent and a perfectionist, she grew increasingly depressed after the marriage ended her career. On the 2nd of May 1915, after an argument with Haber, she died by suicide in the garden, shooting herself in the heart with his service revolver. She did not die at once. Her 12-year-old son, Hermann, had heard the shot and found her.

  The reasons for Clara's death remain a matter of speculation. The marriage had many stresses, and it has been suggested that she opposed his chemical warfare work. On that view, her death may partly answer Haber's personal oversight of the first successful chlorine release at Ypres, which caused over 67,000 casualties. Haber left within days for the Eastern Front to oversee a gas release against the Russian Army.

  On the 25th of October 1917 in Berlin, Haber married his second wife, Charlotte Nathan. He had met her while staying at the Adlon Hotel, near the Deutscher Klub, where she worked as one of the secretaries. Her accomplishments impressed him, though she had no extensive experience or education. On the day they met it was raining, and she lent him an umbrella. He replied, "I lay the umbrella into your arms and myself and my thanks at your feet". She answered, "I'd rather like the contrary".

  Charlotte at first rejected his proposal because of their large age difference, but she eventually agreed. Like Clara, she converted from Judaism to Christianity before the wedding. They had two children, Eva-Charlotte and Ludwig Fritz, known as Lutz. Conflicts returned, and the couple were divorced as of the 6th of December 1927.

  Hermann Haber lived in France until 1941 but could not obtain French citizenship. When Germany invaded France, Hermann, his wife, and their three daughters escaped internment on a French ship sailing from Marseilles to the Caribbean. From there they got visas to emigrate to the United States. His wife Margarethe died after the war, and Hermann died by suicide in 1946. His oldest daughter, Claire, a chemist, died by suicide in 1949, after being told that her research on an antidote for chlorine gas was being set aside because work on the atomic bomb took precedence.

  Haber's other son, Ludwig Fritz Haber, lived from 1921 to 2004 and became an eminent British economist. He wrote a history of chemical warfare in World War I, titled The Poisonous Cloud, published in 1986.

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• 7. Between the Wars

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  From 1919 to 1923, Haber stayed involved in Germany's secret development of chemical weapons, working with Hugo Stoltzenberg. He also helped both Spain and Russia develop chemical gases. In the 1920s, scientists at his institute developed Zyklon A, a cyanide gas formulation used as an insecticide, especially as a fumigant in grain stores. His work was later used, without his direct involvement, to develop the pesticide Zyklon B. That gas was used to kill more than 1 million Jews in gas chambers during the Holocaust.

  From 1919 to 1925, a Japanese businessman named Hoshi Hajime, president of Hoshi Pharmaceutical Company, donated two million Reichsmark to the Kaiser Wilhelm Society. The gift, called the Japan Fund, answered a request from the German ambassador Wilhelm Solf for Japanese support for scholars in financial hardship. Haber was asked to manage the fund and was invited to Japan by Hoshi in 1924. He offered a number of chemical licences to Hoshi's company, but they were refused. The money supported Richard Willstätter, Max Planck, Otto Hahn, Leo Szilard, and others.

  In the 1920s, Haber searched exhaustively for a way to extract gold from sea water and published several papers on it. After years of work, he concluded that earlier researchers had overstated the amount of dissolved gold. The real concentration was far lower, and extraction would be uneconomic.

  By 1931, Haber was increasingly worried about the rise of National Socialism in Germany and about the safety of his friends, associates, and family. The Law for the Restoration of the Professional Civil Service of the 7th of April 1933 targeted Jewish scientists at the Kaiser Wilhelm Society. A journal, the Zeitschrift für die gesamte Naturwissenschaft, charged that founding the Kaiser Wilhelm Institutes had opened the way for an influx of Jews into the physical sciences. It singled out Haber and wrongly called him a nephew of a profiteer named Koppel, to whom he was not related.

  Haber was stunned. He had assumed that his conversion to Christianity and his services to the state in World War I made him a German patriot. Ordered to dismiss all Jewish personnel, he tried to delay their departures long enough to find them somewhere to go. On the 30th of April 1933, he wrote to Bernhard Rust, the national and Prussian minister of Education, and to Max Planck, president of the Kaiser Wilhelm Society. He tendered his resignation as director of the institute and as a professor, effective the 1st of October 1933. He said that as a converted Jew he might be legally entitled to stay, but he no longer wished to.

  Haber and his son Hermann also urged that Haber's children by Charlotte Nathan, at boarding school in Germany, leave the country. Charlotte and the children moved to the United Kingdom around 1933 or 1934. After the war, the children became British citizens. Several members of Haber's extended family were not so fortunate: his half-sister Frieda's daughter, Hilde Glücksmann, her husband, and their two children died in Nazi concentration camps.

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• 8. Exile and Afterlife

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  Haber left Dahlem in August 1933 and stayed briefly in Paris, Spain, and Switzerland. His health was extremely poor, and he suffered attacks of angina. Repeated attacks can cause lasting damage, which likely contributed to his death the following year.

  Some of Haber's former counterparts and competitors from England in World War I now helped him leave Germany. Brigadier Harold Hartley, Sir William Jackson Pope, and Frederick G. Donnan arranged an official invitation to Cambridge. There Haber lived and worked for a few months with his assistant, Joseph Joshua Weiss. Not everyone forgave his role in poison gas. Ernest Rutherford pointedly refused to shake his hand.

  During his brief stay in England in 1933, Haber received an offer from Chaim Weizmann to direct the Sieff Research Institute in Rehovot, in Mandatory Palestine. The institute is now the Weizmann Institute. Haber accepted and left for the Middle East in January 1934, travelling with his half-sister Else Haber Freyhahn. His health gave out on the 29th of January 1934. He died of heart failure, aged 65, mid-journey, in a hotel in Basel, Switzerland.

  Following his wishes, Hermann arranged for Haber to be cremated and buried in Basel's Hörnli Cemetery on the 29th of September 1934. Clara's remains were removed from Dahlem and re-interred with him on the 27th of January 1937. Albert Einstein, his longtime friend, eulogized him: "Haber's life was the tragedy of the German Jew - the tragedy of unrequited love".

  Honors had gathered earlier. Haber became president of the German Chemical Society in 1923 and received the Rumford Medal of the American Academy of Arts and Sciences in 1932. He was elected a Foreign Associate of the National Academy of Sciences of the USA the same year. In 1953, the former Kaiser Wilhelm Institute at Dahlem was renamed the Fritz Haber Institute, and it is part of the Max Planck Society. In 1981, the Minerva foundation of the Max Planck Society and the Hebrew University of Jerusalem established the Fritz Haber Research Center for Molecular Dynamics.

  His life has fed many retellings. The Swedish power metal band Sabaton wrote a song about him called "Father". Vern Thiessen's 2003 play Einstein's Gift portrays him as a tragic figure who tried to evade both his Jewish ancestry and the moral weight of his science. BBC Radio 4 broadcast The Greater Good on the 23rd of October 2008, with Anton Lesser as Haber and Lesley Sharp as Clara. A 2008 short film, Haber, written and directed by Daniel Ragussis, depicted his decision to begin the gas warfare program. Radiolab aired a segment on him in January 2012. Judith Claire Mitchell's novel A Reunion of Ghosts draws on the lives of Haber and Clara, under the names Lenz and Iris Alter. The first season of Genius on National Geographic Channel, which aired from the 25th of April to the 27th of June 2017, portrayed his friendship with Einstein.

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