Mizushima, San-Ichiro

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(b. Tokyo, Japan, 21 March 1899; d. Tokyo, 3 August 1983),

physical chemistry, molecular structure.

One of the pioneers in physical organic chemistry in Japan, San-ichirō Mizushima is internationally known for his investigations, from the mid-1920s, of the molecular structures of organic compounds with physical instrumentation, such as radio waves, Raman spectroscopy, infrared spectroscopy, and electron diffraction. Most notably, he elucidated internal rotation around a C-C single bond and discovered the “gauche” form of rotational isomers around 1940.

Early Life and University Education . Mizushima was born in Nihonbashi, Tokyo (Edo), the eldest son of an affluent merchant dealing with luxurious gold-woven textiles for kimonos, whose family business dates back to the eighteenth century. Destined to enter the family business, Mizushima received a sophisticated education at prestigious secondary and higher schools in Tokyo, especially in Western languages, as his family had business dealings with Western countries. He was therefore not particularly encouraged to follow a scientific career. The decline of his family business in his boyhood prompted him to seek another career, and Mizushima chose chemistry, his primary interest in elementary and secondary school, as his major. His choice of career should therefore be regarded as a product of Japanese science education at the elementary and secondary levels established in the mid-Meiji period in the 1890s, rather than as a reflection of his family background, which had often been the case in the early Meiji period in the 1870s. He entered the Department of Chemistry, the Faculty of Science of Tokyo Imperial University, in 1920, and graduated in 1923, when he became an assistant there to his former teacher, Japanese physical chemist Masao Katayama.

As Mizushima himself wrote in 1972, the Department of Chemistry at Tokyo Imperial University had a tradition in physical chemistry. Jóji Sakurai, virtually the founder of the department, had studied chemistry at University College London in England between 1876 and 1881 with Alexander William Williamson; he had assimilated his mentor’s dynamic view of the atomic constituents of molecules and “physicalist” approach to chemistry, which emphasized the importance of studying physical properties of chemical substances with instrumentation used in experimental physics, before being appointed as one of the first Japanese chemistry professors at Tokyo in 1882. Sakurai argued, as early as the early 1880s, that chemistry in the future should be “chemical dynamics,” that is, “the science of studying the changes caused by the vibration and motion of atoms,” and that chemists would have to clarify the truths of chemistry from the viewpoint of physics to advance the science further. This agenda remained an elusive dream during Sakurai’s short career as a research chemist during the 1880s and 1890s, but his strong presence provided a favorable condition for the development of physical chemistry in Tokyo’s Department of Chemistry.

Mizushima’s mentor, Katayama, had chosen physical chemistry as his area of specialization under Sakurai’s influence. After graduating from the Department of Chemistry at Tokyo in 1900, Katayama did overseas study (then a prerequisite for Japanese academics for further promotion) at the University of Zürich, Switzerland, with the electrochemist Richard Lorenz and at the University of Berlin, Germany, with the physical chemists Walther Nernst and Max Bodenstein between 1905 and 1909. He was appointed the first professor of physical chemistry at the newly established Tóhoku Imperial University in Sendai, Japan, in 1911 and then succeeded Sakurai as the professor of physical chemistry at Tokyo in 1919. Influenced by Sakurai’s pro-atomistic view—and being aware of the contemporary methodological arguments about the role of hypotheses in science, most notably the “energetics” of the German physical chemist Wilhelm Ostwald— Katayama positively adopted atomism as a working hypothesis and published an influential textbook of physical chemistry based on chemical thermodynamics in Japanese, Kagaku Honron (Fundamentals of chemistry), in 1914.

Katayama chose theoretical investigations in surface and colloid chemistry, based on his molecular interpretation of thermodynamics and later on the quantum theory, as his research field. His most important research outcome was “Katayama’s equation” published in 1916, an equation describing the relationship between surface tension and the temperature of liquids, which he derived from the theory of corresponding states proposed by the Dutch physical chemist Johannes Diderik van der Waals. Katayama is said to have assigned to his students experimental investigations related to his theoretical considerations in surface and colloid chemistry. Indeed, according to Mizushima’s recollection in his article published in Kagakushi in 1975, Katayama assigned a chemical investigation using radio waves to Mizushima around 1923, hoping that he might be able to “discover proper oscillations of colloidal particles whose frequencies should be within a range much lower than those of molecular internal vibrations” (p. 1). Mizushima could not discover what he had hoped for, but his investigation led to the first experimental support for the theory of electric moments involving dielectric constants developed by the Dutch-born physicist Peter Debye between 1912 and 1913.

Anomalous Dispersion and Absorption of Radio Waves and Dipole Moments . Debye’s theory was concerned with an explanation of the change of the dielectric constants of polar substances with varying temperature as well as with varying frequency of external alternating electric field by postulating the existence of permanent dipoles within organic molecules. He proposed this theory in the context of the emergence of polar explanations of organic reactions and the growing interest in polarity within organic compounds in the 1900s and 1910s. According to this theory, in a static or slowly alternating external electric field, organic molecules with permanent dipoles would be oriented in the direction of the electric field causing an increase in dielectric constant, against their temperature-dependent thermal movements after “the time of relaxation” of molecules, which is proportional to the viscosity and the cube of radii of molecules and inversely proportional to the absolute temperature. As the period of alternating electric field would approach the time of relaxation, the orientation of the polar organic molecules could no longer follow the change of electric field. As a result, their contribution to the dielectric constant would disappear, and anomalous dispersion and dielectric loss (absorption of radio waves) would occur. For lack of experimental supports, however, this theory had failed to attract much attention on the part of chemists.

Mizushima’s research on dispersion of radio waves (or “electric waves” as Mizushima put them in his papers in English, probably following the Japanese word for radio waves, denpa) by glycerin and monovalent alcohols reveals attributes that characterized his research style throughout his career: his ingenuity in constructing physical instrumentation by hand, his skill of networking for interdisciplinary collaborations, and his intellectual prowess in interpreting his experimental findings with available theories. With the technical support of his colleagues in electric engineering at Tokyo, Mizushima first constructed several oscillators emitting radio waves with different wavelengths of 3.08, 6.1, 9.5, and 50 meters and later of 58 centimeters. According to his recollection in 1975, “if I had been an electric engineer, I would then have endeavored to make radio waves of even shorter wavelengths. However, as I was an apprentice chemist, I came across the idea of measuring [dielectric constants of glycerin and alcohols] using available radio waves in continuously changing temperatures” (p. 1). He thus obtained temperature-dielectric constant and temperature-dielectric loss diagrams of glycerin and several monovalent alcohols in several wavelengths. Mizushima argued, based on his data, that Debye’s dipole theory held well in all monovalent alcohols that he examined; he published his finding in English in the Bulletin of the Chemical Society of Japan, the newly inaugurated Western-language journal of the Nihon Kagaku-kai (Chemical Society of Japan), in 1926.

The idea of continuously changing temperatures proved a key in Mizushima’s investigation leading to an experimental support of Debye’s theory. However, the above quote suggests that, in doing so, he seems to have been guided not by theories but by his instinct as a physical chemist, for whom temperature control was a standard experimental procedure. The role of Debye’s theory for Mizushima was to give a physical meaning to his measurement and to pave the way for the extensive subsequent measurements of the dipole moments of molecules. It is no wonder that Debye was pleased to read Mizushima’s papers, arranged the publication of their summary in the prestigious Physikalische Zeitschrift in the following year, and explained Mizushima’s findings in detail in his monograph, Polare Molekeln (Leipzig, Germany, 1929).

Mizushima was promoted to assistant professor at Tokyo in 1927, did overseas study between 1929 and 1931 at the University of Leipzig, Germany, with Debye, and was awarded a Rigaku Hakushi gó (doctorate of science) from Tokyo Imperial University in absentia in 1930. In Leipzig Mizushima spent the majority of his time learning quantum mechanics and its application to chemistry. As Debye’s laboratory was then concerned with the investigation of the structures of gas molecules by means of gas-phase electron diffraction, it is likely that Mizushima came across the idea of investigating internal rotation around a C-C single bond in 1,2-dihalogenoethane during his overseas study by learning about the paper of Hermann Mark and Raimund Wierl in 1930. They argued that the two chlorine atoms in this molecule are approximately in the cis- and trans- positions according to gas-phase electron diffraction, contrary to the assumption that the rotation around single bonds such as C-C was free, as had been thought since the establishment of stereochemistry by Jacobus Hendricus van't Hoff and J. A. Le Bel in the 1870s.

Internal Rotation and the Discovery of Rotational Isomerism. The key research question for Mizushima was therefore whether rotation around single bonds such as C-C was actually free or whether there were some stable forms. Mizushima started this project in 1932, soon after he returned from Germany. This time he chose to adopt emerging multiple techniques for the investigation of molecular structures such as Raman spectroscopy, infrared spectroscopy, and electron diffraction, as well as the measurement of dipole moments. For this purpose, Mizushima used his extended interdisciplinary networks with manufacturers of optical instruments and physicists at Tokyo Imperial University and the Rikagaku Kenkyújo (Riken, the Institute of Physical and Chemical Research, established in 1917), where Katayama had held the additional post of researcher; Mizushima assumed the same office in 1934. As he broadened his research front, he felt the necessity to recruit students and to organize a research group. With the support of his former teacher and superior Katayama (Mizushima succeeded Katayama as full professor of physical chemistry in 1938), he was able to recruit advanced students for his research and to build a well-coordinated research group consisting of students of both Katayama and himself, such as Ken-ichi Higashi, Yonezó Morino, and Takehiko Shimanouchi.

The starting point was in his familiar territory, that is, the measurement of temperature changes in the dipole moment of 1,2-dichloroethane in solution with Higashi. Within a year, in 1932, they found that its dipole moment increased when measured at higher temperature or in solvents with higher dipole moment. According to Mizushima’s interpretation, this finding suggested some sort of rotation around a C-C single bond within molecules. At the same time, Mizushima, with suggestions and technical advice from the spectroscopist and physicist at the Riken, Yoshio Fujioka, decided to adopt Raman spectroscopy and assigned the measurement of its Raman spectra to Morino.

Without prior research experience in spectroscopy of any kind, it took some time for Morino to master Raman spectroscopy. However, the technological situation in Japan in the 1930s was encouraging for starting such a research project because, as he later recalled in his obituary of Mizushima in 1983, “the advancement of domestic production of optical weapons such as periscope of submarines was strategically important for Japan at that time. An investigation of glass was well underway in the Nihon Kógaku (Japan Optics Manufacturing Company, today’s Nikon), and the technology of removing distortion of glass has just completed there” (p. 1286). Morino constructed handmade Raman spectrographs with the lenses and prisms provided by Masao Nagaoka, an engineer of the Nihon Kógaku and lifelong friend of Mizushima from his secondary school days. After several attempts, Morino succeeded in 1934 in taking photographs of the Raman spectra of 1,2,-dichloroethane in the liquid state and in solutions. Later in 1936 he took photographs of the Raman spectra of this and other ethylene halides in the solid and liquid states, which showed that several Raman lines in the liquid state disappear on solidification.

Combining this result with the data of dipole measurements by Higashi and the theoretical calculation of normal vibration frequencies and intramolecular potential of this molecule by Morino and Shimanouchi, Mizushima inferred that 1,2-dichloroethane molecules occurred only in the symmetrical trans- form in the solid state, and that in the liquid state another rotational isomer existed. According to his interpretation, this new form was not the cis- form, but could be obtained from the trans-form by an internal rotation of about 120°; Mizushima’s interpretation, together with the above-mentioned result of Morino’s Raman spectra measurement, was first published in 1936 in his “home” journal as a Riken researcher, Scientific Papers of the Institute of Physical and Chemical Research, Tokyo in English, and then in the Physikalische Zeitschrift in German in the following year. Increasingly convinced of the existence of this new configuration by his similar researches with other compounds with C-C single bonds, Mizushima coined the term gauche form in 1940 to designate it with the help of the Japanese organic chemist and x-ray crystallographer, Isamu Nitta, professor of physical chemistry at Osaka Imperial University, Japan, and a close friend of Mizushima from school days; Mizushima began to use it in his publications in Scientific Papers in 1940 and in the U.S.-based Journal of Chemical Physics in 1941.

These interpretations were later confirmed by gas-phase electron diffraction of 1,2-dichloroethane molecules by Morino in collaboration with Shigeto Yamaguchi, a former student of Mizushima working at Riken, in 1943, which showed that around 20 percent of all molecules were in the gauche form at room temperature. Between 1946 and 1959, when Mizushima retired from the University of Tokyo (Tokyo Imperial University was renamed the University of Tokyo in 1947), the investigation of internal rotation in his laboratory was extended to other single bonds such as C-O, C-N, C-S, and S-S, using the above-mentioned techniques as well as thermal infrared spectroscopy and analysis measuring energy and entropy differences. By these extended researches his team confirmed that the gauche form existed not only in a C-C single bond, but also in a variety of single bond skeletons of both organic and inorganic compounds.

Mizushima’s research on internal rotation gained international recognition after the end of World War II, especially in the United States. In 1951 he was invited by Cornell University to give the G. F. Baker Lectures in chemistry and by the University of Notre Dame, Indiana, to give the P. C. Reilly Lectures in chemistry; he thereafter gave special lectures at various universities in the United States as well as in Europe during summer vacations. Mizushima kept a particularly close relationship with the University of Notre Dame and held a visiting professorship there during the 1950s, partly because he and his wife, Tokiko (she was from the Shóda family and an aunt of Empress Michiko, consort of Emperor Akihito), were Roman Catholic. He was elected in 1955 a bureau member of the International Union of Pure and Applied Chemistry and held this position until 1967.

Structure of Proteins . Mizushima’s discovery of the rotational isomers of 1,2-dichloroethane can arguably be regarded as one of the earliest examples of conformational analysis, which saw considerable development in the chemistry of alicyclic compounds and polymers in the 1950s. In addition, during World War II, Mizushima undertook several wartime researches, such as Raman spectroscopic analysis of paraffin in petroleum and polymers as the material of radar. After the war, Mizushima, in collaboration with Shimanouchi, who had research experiences in infrared spectroscopy and in the calculation of long-chain molecular vibrations, turned his attention to the structure of proteins, which was an unexplored area in physical chemistry of polymers.

Understandably, the starting point of the investigation of proteins by Mizushima and Shimanouchi was the trans- and gauche-form of rotational isomers of C-C and C-N single bonds, which constitute polypeptide chains. They postulated in 1947 the “B (Bent) form” and led students’ works in Raman and infrared spectroscopy and in calculations of molecular vibrations of peptides and proteins to support this model. Unfortunately for Mizushima and Shimanouchi, their B model failed to gain international recognition, as the “α-helix” model proposed by Linus Pauling in 1951 soon prevailed in the fast-growing field of molecular biology and biochemistry. However, Mizushima and Shimanouchi accumulated experimental and theoretical know-how in protein chemistry by this project and trained a considerable number of students who later developed their careers in biological physical chemistry and molecular biology.

Mizushima retired from the University of Tokyo in 1959 at the age of sixty following the University of Tokyo custom of forced retirement taken up by Sakurai and other professors in 1919; he was succeeded by Shimanouchi. Mizushima moved to corporate research and was instrumental in establishing the Tokyo Research Institute of the Yahata Seitetsu (Yahata Steel Manufacturing Company) as director. He remained there for ten years.

Mizushima’s research style as a physical chemist is characterized, first of all, by his interpersonal skills in recruiting young chemists and networking with scientists and engineers in different fields. His educational background of having attended prestigious secondary and higher schools in Japan and his connections with Tokyo Imperial University and Riken scientists and engineers counted much in setting up his electronic and spectroscopic investigations, even though he had had comparatively little research experience in these fields. Second, Mizushima’s research consisted of frequent movements between experimental investigations and theoretical considerations. He eagerly assimilated Debye’s theory of polar molecules and quantum mechanics to interpret his experimental results and to give coherence to the development of his research field. However, a theory was for Mizushima but “a summary of the nature.” He was clearly more interested in finding experimental facts unpredictable by existent theories than the construction of a theory with known experimental facts.

Mizushima’s way of managing laboratory spaces reflected his emphasis on the discovery of unpredicted experimental facts by means of exchange of ideas: As soon as he was appointed full professor, he allocated a large room next to his office for students and encouraged discussion between teachers and students and among students there. This room was designed so that Mizushima could enter his office only by passing through this large student room. Discussion in this room was seemingly unconstrained, but in fact was under the watchful eye of Mizushima, who was always hungry for new ideas and experimental data. Mizushima built a successful research school on a careful balance between freedom and constraint given to his students and associates.


The Scientific Papers of Professor S. Mizushima: A Collection Presented by His Friends and Pupils on the Occasion of the Celebration of the Completion of His Thirty-Sixth Year as a Member of the Faculty of the University of Tokyo (University of Tokyo, 1959) is a select collection of Mizushima’s scientific papers; it contains a complete list of his scientific publications, a short biography, and useful surveys of his researches by his collaborators such as Higashi, Morino, and Shimanouchi.


Structure of Molecules and Internal Rotation. New York: Academic Press, 1954. Mizushima’s only monograph in English.

“A History of Physical Chemistry in Japan.” Annual Review of Physical Chemistry 23 (1972): 1–14. Mizushima’s personal view of the history of physical chemistry in Japan.

“Bunshi Kagaku (Kózó Kagaku) no Hajimatta Koro” [On the early years of molecular science or structural chemistry]. Kagakushi 3 (August 1975): 1–3. Mizushima’s recollection of his research on abnormal dispersion and absorption of radio waves.

“Hitoketa no Jikken” [Experiments of the first order]. Kagaku to Kogyo 36 (1983): 727–728. Published posthumously, this article contains information on his collaborative research of internal rotation.


Baba Hiroaki, Tsuboi Masamichi, and Tazumi Mitsuo, eds. Kaisó no Mizushima Kenkyushitsu [Mizushima Laboratory in reminiscences]. Tokyo: Kyóritsu Shuppan, 1990. Collected recollections by Mizushima’s students. Useful for outlining the Mizushima school, especially during and after World War II.

Higashi Ken-ichi. “Denpa no ijó bunsan to kyúshú ni kansuru kenkyu” [[Mizushima's] Research on anomalous dispersion and absorption of radio waves]. Tanpakushitsu Kakusan Koso 28 (1983): 1285–1286. An obituary in Japanese by his collaborator.

Kikuchi, Yoshiyuki. “The English Model of Chemical Education in Meiji Japan: Transfer and Acculturation.” PhD diss., Open University, 2006. See Chapters 4–7 for an account of Sakurai.

Kuchitsu, Kozo. “Early Days of Gas Electron Diffraction Studies in Japan.” Structural Chemistry 16 (2005): 29–32. An English article on Morino, which also mentions his collaboration with Mizushima.

Mizushima Keiichi, ed. Mizushima San-ichiró: Sono Omoide [San-ichiro Mizushima and his reminiscences]. Tokyo, 1984. Recollections by Mizushima’s family members and personal friends. Useful source on his family background.

Morino, Yonezo. “Obituary: Takehiko Shimanouchi.” Journal of Raman Spectroscopy 12 (1982): ii–iv. Also mentions Shimanouchi’s collaboration with Mizushima.

_____. “Mizushima San-ichiro Sensei to Bunshi Bunko” [Professor San-ichiro Mizushima and molecular spectroscopy]. Tanpakushitsu Kakusan Koso 28 (1983): 1286–1287. An obituary in Japanese by his collaborator.

Tamamushi Bunichi. “Kaimen Kagaku eno Michi: Takayama Masao Kyóju Seitan 100-shúnen ni chinande” [The way to surface chemistry: In memory of centennial birth of Professor Masao Katayama]. Kagakushi 8 (October 1978): 1–6. Personal account of Katayama’s work by his student in surface chemistry.

Tsuboi Masamichi. “Mizushima San-ichiro Sensei no Kenkyu Sokuseki” [On the works of Professor San-ichiro Mizushima]. Kagakushi 22 (1995): 142–151. Survey of Mizushima’s research by one of his students.

Yoshihara Kenji. “Kaiten iseitai no hakken: Mizushima Sanichiro Sekai wo meguru Gauche no Hankyo” [The discovery of rotational isomers: San-ichiro Mizushima and the reaction to the gauche form all over the world]. Gendai Kagaku 403 (October 2004): 14–19. Accessible guide to Mizushima’s researches.

Yoshiyuki Kikuchi