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Fritz Haber is one of the most important and controversial scientists of the 20th century.

How many chemists have been the subject of multiple plays, television documentaries, and graphic novels? How many scientists can report that their discoveries have helped feed billions? Or maimed millions? Haber has been called many things: scientific genius, war criminal, Jew, husband and father, and friend and colleague. Here we examine many sides of the man who oversaw the first chlorine gas attack of World War I.

Scientific Genius

Enlarge Haber in his lab. Credit: Archiv der Max-Planck-Gesellschaft, Berlin

At the turn of the 20th century, humanity faced the prospect of incredible famine. One concerned chemist, William Crookes, predicted in 1898 that “millions will starve to death due to lack of nitrogen fertilizer for plant growth.” Nitrogen was abundant in the air, but it was out of reach for those who wanted it for industrial-scale fertilizer production. Fritz Haber, though, put his mind toward harnessing it to make fertilizer at a volume that could help feed Earth’s growing population.

Some mix of Haber’s vast intellect—he was already an accomplished electrochemist in Karlsruhe, Germany—and his appreciation of applied science—he spent the early part of his career working in his father’s dye business as well as at an alcohol distillery, a cellulose factory, and an ammonia-soda factory—helped him invent a straightforward strategy for nitrogen fixation. The achievement garnered Haber the 1918 Nobel Prize in Chemistry. Although his strategy paved the way for making fertilizer from air, Carl Bosch made the discovery workable on an industrial scale by replacing the expensive osmium or uranium catalysts Haber’s process called for with cheaper magnetite and aluminum oxide ones. The Haber-Bosch process remains the workhorse of this industry.

Because fertilizer gets incorporated into the agricultural products we eat, an estimated 40% of the essential nitrogen in every human’s body now originates from the Haber-Bosch process. Yet in a perfect example of how one discovery can benefit humanity just as easily as it can destroy it, the Haber-Bosch process was also vital to manufacturing nitrogen-based explosives for the German Army during World War I.

Haber’s scientific genius was multifaceted. He made important developments in organic chemistry (his doctoral thesis was on derivatives of the fragrance molecule piperonal, found in pepper, dill, and vanilla), his work on molecular adsorption formed the basis of Irving Langmuir’s now-classic theory of adsorption, and he developed a whistle device for alerting miners of toxic fumes. He also put his mind to weaponizing toxic compounds during WWI, particularly chlorine, phosgene, and mustard gas, which led to the first large-scale deployment of chemical weapons in history.

War Criminal

Enlarge Haber (pointing) instructs soldiers about chlorine gas deployment in WWI. Credit: Archiv der Max-Planck-Gesellschaft, Berlin

After World War I, the Allies named Fritz Haber a war criminal and requested his extradition, prompting the chemist to hide in Switzerland in 1919.

The Allies took that action because Haber proposed the use of chlorine gas on Allied troops to the German High Command in 1914, a recommendation that was in direct contravention to a 1907 international agreement against the use of poisonous weapons. He then worked to weaponize the gas: He oversaw its deployment first in Ypres, Belgium, then elsewhere; he led the development of at least two other chemical weapons deployed in WWI, phosgene and mustard gas; and he advocated the use of chemical weaponry until his death in 1934.

Haber’s name was later removed from the Allied war criminal list, and he returned to Berlin as a war hero. What the Allies did not know is that during the postwar period, going against the Treaty of Versailles, Haber secretly continued poisonous gas research.

Haber ignored the near-universal testimonials of soldiers, nurses, and doctors that described the horrors of poison gas, notes Joseph Gal, a chemical historian at the University of Colorado, Denver. As John Ellis wrote in the book “Eye-Deep in Hell: Trench Warfare in World War I,” “With mustard gas the effects did not become apparent for up to twelve hours. But then it began to rot the body, within and without.” Haber strongly believed poisonous gas was a more humane form of weaponry compared with standard artillery, and he argued that it would bring WWI to an end quickly. It did not.

The Haber-Bosch process did, however, boost production of traditional weaponry during WWI. Scientists used this nitrogen fixation strategy to make nitrate-based explosives. According to several military historians, after a year or two of war, Germany would have run out of explosives had it not been for the Haber-Bosch process.

Jew

Enlarge Haber as a Ph.D. student. He converted to Lutheranism around this time. Credit: Archiv der Max-Planck-Gesellschaft, Berlin

Much is made of Fritz Haber’s German Jewish heritage, and rightly so: He was born in 1868to a Jewish dye merchant, he faced anti-Semitism throughout his life, and he died a Third Reich Jewish exile in Basel, Switzerland, in January 1934.

Both of Haber’s wives were of Jewish descent, as were his closest friends. Haber became the first head of the Kaiser Wilhelm Institute for Physical Chemistry & Electrochemistry, now known as the Fritz Haber Institute, because its benefactor, a Jewish banker named Leopold Koppel, agreed to finance the institute only if Haber was its director.

Yet Haber converted to Christianity as a young man and spent his entire adult life—some 40 years—as a Lutheran. This conversion was a “gesture of opportunistic conformity,” writes Fritz Stern, a historian at Columbia University and Haber’s godson (Angew. Chem. Int. Ed. 2012, DOI: 10.1002/anie.201107900). Many Jews in that era converted so that they could still attain their career objectives despite Germany’s anti-Semitic culture. “Haber embraced the new religion with more fervor than inner faith—in the service, I think, of one overriding genuine passion: his pride in being German, his loyalty, even subservience to Germany’s rulers,” Stern writes.

Immerwahr, Haber’s first wife, was one of the first female Ph.D. chemists in Germany. She committed suicide after the first WWI gas attack.

Credit: Wikimedia Commons

When Adolf Hitler came to power in 1933, Haber’s daughter, Eva Lewis, then 15 years old (now 96), recalls, Haber sat her and her brother down to explain that they were of Jewish descent. “We didn’t know,” Lewis told C&EN. It was “possibly the first real shock I had in my life—to be suddenly told, ‘Well, you’re Jewish, according to that man Hitler.’ ”

Husband & Father

Enlarge Haber weds his second wife, Nathan. His son Hermann, from his first marriage, stands to the left. Credit: Archiv der Max-Planck-Gesellschaft, Berlin

Fritz Haber married twice and fathered three children. In 1902 Haber had his first son, Hermann, with his wife, Clara Immerwahr, one of the first female Ph.D. chemists in Germany. Their marriage soon turned rocky because of Haber’s traditional family values, Immerwahr’s frustrated career aspirations—she went from being an active chemist to a housewife—and the family’s financial difficulties. Immerwahr also strongly objected to Haber’s work on chemical weapons. A week after the first gas attack in Ypres, Belgium, in 1915, she shot herself. Their son, Hermann, nearly 13 years old, found his mother dying. Haber left for the Eastern Front the following day to prepare for a gas attack on Russian troops.

Credit: Wikimedia Commons

Two years later, in 1917, Haber married his second wife, Charlotte Nathan, who worked at a social club he attended. Nathan was intelligent, but not an intellectual like Immerwahr, Colorado’s Gal notes. Nathan was fiercely independent, though; they divorced a decade later. From the second marriage came two children, a daughter, Eva, and another son, Ludwig.

Hermann had a sometimes tumultuous relationship with his father. Haber objected to Hermann’s desire to study law and forced him to pursue chemistry instead. Hermann was also a source of contention for Haber’s second wife: In her memoirs, she says that their marriage’s first and last fights were about Hermann. Despite their problems, Hermann was at his father’s side the night Haber died of a heart attack in 1934. Although Hermann was never able to fully get his career going, he eventually worked in patent law before committing suicide in 1946, shortly after his own wife died of cancer.

If Haber was preoccupied with Hermann, he had a modest interest in his younger two children. According to his daughter, Eva, now 96, Haber didn’t treat them badly. “There was just a sheer lack of interest,” she says. He’d ask, “ ‘Do they have enough to eat and to drink, and [are they] dressed properly and do they speak properly and are they schooled properly?’ Beyond that, I don’t think he had any particular interest in us.”

Dear Friend & Colleague

Enlarge Haber and his friend Einstein in Berlin. Credit: Archiv der Max-Planck-Gesellschaft, Berlin

Fritz Haber was, by many accounts, a devoted friend. One of his closest friends, 1915 Chemistry Nobel Laureate Richard Willstätter, wrote that “the most beautiful trips were the ones I took with Fritz Haber; they were hours of friendship in which I came to know and understand his individuality, his noble mind, goodness of heart, wealth of ideas, and his boundless extravagant drive.”

Haber often took trips to recuperate at spas after overextending himself with work and wrote charming postcards to his friends and family in rhyme. Here’s an excerpt from a poem he wrote for Albert Einstein:

I walked a whole day—or very near—

To see Sturmann’s cave and the ravine

But had to leave them both unseen:

My body’s strength denied my desire.

This is the pain, this is the inner fear:

Will you persist in what you have begun

When autumnal storms of life about you run

And around your steps, cold fogs drear?

Haber and Einstein were very different individuals: Einstein was flamboyant; Haber conservative. Einstein was a proud Jew; Haber a proud German. Einstein was critical of Germany; Haber loyal to this nation. Yet the two developed a friendship: When the Third Reich robbed Haber, one of Germany’s proudest citizens, of his job and disowned him, Einstein wrote him to say: “I can imagine your inner conflicts. It is similar to having to give up a theory that one has worked on all one’s life.”

Another one of Haber’s closest friends was his physician, Rudolf Stern. Stern’s son Fritz was Haber’s namesake and also his godson. In an article about his Onkel Fritz, the younger Stern, now an emeritus historian at Columbia University, writes, “Haber was hailed not only for his own achievements but also for his tireless furtherance of others, for the quick brilliance with which he grasped the core of a problem and intuited a solution.”

During the Third Reich, most chemists adopted Hitler’s anti-Semitic policies without contest, and many actively participated in research programs that advanced Hitler’s goals. Yet one certain act of defiance against the regime was Max Planck’s attempt to organize a memorial for Haber in 1935, a reflection of the esteem in which Haber was held by his colleagues, some of whom attended at great personal risk.