Eligio Perucca: serendipity across the Atlantic

By Davide Viterbo
DISTA, Università del Piemonte Orientale, Via V. Bellini 25/G, 15100 Alessandria, Italy.

I intend to tell of a remarkable episode that occurred to me in the summer 2007 while I was attending the ACA congress in Salt Lake City.
In the special section dedicated to the Fankuchen prize attributed to Frank Herbstein, the last speaker was Bart Kahr of the University of Washington at Seattle, whom I did not know. The title of the presentation “Eligio Perucca first observed induced optical activity in 1919” arose my curiosity. Old remembrances came to my mind of a terrible physics professor of the Politecnico di Torino, a real terror of many generations of engineering students, among which I also had some friends. I was never his student, but I still have in my office shelves the two volumes of his very clear Physics textbook, full of detailed descriptions and beautiful pictures of old and now obsolete instruments. Why was he recalled in the Mormon’s city?
Bart Kahr told us a fascinating story, mixing history and crystallography in a speech full of humor. I learned that in a 1919 paper (Nuovo Cimento, 1919, 18, 112-154) Perucca had anticipated, without being aware, the discovery of two important effects: i) induced optical activity, normally attributed to Pfeiffer (Chem. Ber. 1931), and ii) enantioselective adsorption on chiral crystals normally attributed to Bonner (Science, 1974). Khar and his colleagues tried to repeat with modern instruments Perucca’s experiments, in which he had measured the rotatory power of chiral NaClO3 crystals grown in the presence of a racemic mixture of a blue dye. Some signs of his anticipations emerged and the terrible Professor Perucca in the Seattle lab became an unknown hero. Khar then tried to get some information on this character and found just an article by V. De Alfaro (a theoretical physic professor in Torino, I know) in which Perucca was described as “un personaggio bizzarro”. He then read in the biography of Primo Levi by M. Anissimov that Perucca had been one of the professors who in 1941 refused to assign a thesis to Primo Levi (another Turinese) because he was Jewish.1 The hero then became a “bizarre fascist”.
Struck in the pride of my roots, I could not refrain from intervening and I jumped towards the microphone. After citing one of the many episodes of Perucca’s terrible reputation with the students (I suppose the term “bizzarro” referred to it), I pointed out that I doubted of what reported by M. Anissimov on the basis that Levi was a chemistry student by the University of Torino, while Perucca was teaching physics at the Politecnico, which is a completely separate academic institution. I also added that in those times all had to show sympathy to the regime. I then promised that I would further investigate the story when back in Torino.
An immediate friendship with Bart was the best present of the episode and someone (I am sorry I do not remember who) took a picture of us. Joel Bernstein, who was chairing the session, was also very impressed by the event and in his description on “ACA RefleXions” he wrote: “As it happened, Kahr’s tales of Perucca provided the impetus for a rare and truly memorable moment. Unbeknownst to Kahr, the audience was graced by the presence of Davide Viterbo……. Even before Kahr completed his lecture, Viterbo requested – and was granted - permission to approach the microphone and relate a few personal accounts, confirming Kahr’s anecdotal tales of Perucca’s classroom tyranny. The question of whether Perucca had first observed induced optical activity is still open to debate, but the lecture, and the atmosphere created by that incident and the day long sharing of academic experiences by the speakers provided a fitting close to a unique day of award symposia honoring two distinguished members of the crystallographic community. It was the stuff memories are made of”.

Back in Torino I started my search, but at the Politecnico I could not find much. I contacted Vittorio De Alfaro and interviewed several other people who had known Perucca. They all agreed that Perucca was a sincere and convinced anti-fascist. This was also confirmed by Luigi Radicati di Brozolo, now a retired professor of the University of Pisa, who was Perucca’s assistant. He did not know anything about the 1919 paper or of Levi’s thesis, but he remarked that Perucca was strict only with dunce students. Recently, through a colleague, I was introduced to Perucca’s nephew Gianni Perucca, who again confirmed Radicati’s words.
At the same time I contacted several people who knew Primo Levi. Unfortunately I could not get any definite proof against or in favour of Anassimov’s statement, except that all the people I interviewed agreed that Anassimov’s biography is rather unreliable and with many unchecked assertions. I also asked my friend Renato Portesi, who was Primo Levi workmate for more than 10 years at SIVA, a varnish factory near Torino. He told me that once he took a sample to test to the Physics Department of the Politecnico and when he came back Primo Levi mentioned Perucca and said that he and some other anti-fascist fellows attended some of Perucca’s lectures because he was known to make indirect but clear anti-fascist remarks. Finally I sent a letter to Primo Levi’s sister Anna Maria, who lives in Rome and she was so kind to ring me back. She also did not know who were the professors that refused the thesis to her brother, but was very clear in criticizing Anassimov’s biography, in which three professors are mentioned: G. Ponzio, M. Milone and E. Perucca.
In the “Potassium” account Levi tells how he met “the assistant” (Nicola Dellaporta), who allowed him into his lab. He wanted an experimental thesis, but Jews were not allowed in the labs and he had to be content of a descriptive dissertation on Walden inversion signed by Professor Ponzio. Milone was Ponzio’s assistant and he was later (1959) my professor of Physical Chemistry. I suppose Perucca was added because he was famous in Torino.
In conclusion I only have two certainties: Perucca was not fascist and Anassimov’s biography can not be taken for granted. Unfortunately this is all I could get, but I must confess that I enjoyed this historical search and I thank Bart for stimulating it.

Bart Kahr, Yonghong Bing, Werner Kaminsky, Davide Viterbo "Turinese Stereochemistry: Eligio Perucca's Enantioselectivity and Primo Levi's Asymmetry", Angewandte Chemie International Edition 2009, 48, 3744–3748.