Eligio Perucca (28 March 1890 in

Potenza Potenza (, also , ; , Potentino dialect: ''Putenz'') is a ''comune'' in the Southern Italian region of Basilicata (former Lucania). Capital of the Province of Potenza and the Basilicata region, the city is the highest regional capital and one ...

– 5 January 1965 in Rome) was an Italian

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

instructor and researcher at the

University of Turin The University of Turin (Italian: ''Università degli Studi di Torino'', UNITO) is a public research university in the city of Turin, in the Piedmont region of Italy. It is one of the oldest universities in Europe and continues to play an impo ...

in Italy in the early decades of the twentieth century. He later served a professorship at the nearby Polytechnic University of Turin. He discovered an important principle in

stereochemistry Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms that form the structure of molecules and their manipulation. The study of stereochemistry focuses on the relationships between stereois ...

in 1919, but his contribution was overlooked and forgotten until recently.

Life and career

Perucca received a Ph.D. degree in physics from the

University of Pisa The University of Pisa ( it, Università di Pisa, UniPi), officially founded in 1343, is one of the oldest universities in Europe. History The Origins The University of Pisa was officially founded in 1343, although various scholars place ...

at the astoundingly young age of 20. He became Assistant to Professor Naccari in 1911 at the

, a post he retained for 11 years. In 1922 Perucca succeeded Professor Majorana to the chair of Experimental Physics at the

Polytechnic University of Turin The Polytechnic University of Turin ( it, Politecnico di Torino) is the oldest Italian public technical university. The university offers several courses in the fields of Engineering, Architecture, Urban Planning and Industrial Design, and is co ...

. He retained that appointment until 1960. In addition he was Rector of the Polytechnic from 1947–1955, and largely devoted his energy to rebuilding the physical facilities which had been destroyed during World War II.

Scientific achievements

Upon arriving at the University of Turin, Perucca launched into the study of

polarized light Polarization (also polarisation) is a property applying to transverse waves that specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of the ...

. In 1913 he invented a sensitive

light meter A light meter is a device used to measure the amount of light. In photography, a light meter (more correctly an exposure meter) is used to determine the proper exposure for a photograph. The meter will include either a digital or analog calcul ...

known as the ''Bilamina de Bravais-Perucca'', which is still highly regarded for its precision. In a paper published in 1919, Perucca reported an experiment which produced

optical rotatory dispersion Optical rotatory dispersion is the variation in the optical rotation of a substance with a change in the wavelength of light. Optical rotatory dispersion can be used to find the absolute configuration of metal complexes. For example, when plane-pol ...

(ORD) as a result of passing linearly polarized light through colored

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

s of

sodium chlorate Sodium chlorate is an inorganic compound with the chemical formula Na ClO3. It is a white crystalline powder that is readily soluble in water. It is hygroscopic. It decomposes above 300 °C to release oxygen and leaves sodium chloride. Sever ...

. Perucca was attempting to replicate a nineteenth-century experiment (1860) in which

amethyst Amethyst is a violet variety of quartz. The name comes from the Koine Greek αμέθυστος ''amethystos'' from α- ''a-'', "not" and μεθύσκω (Ancient Greek) / μεθώ (Modern Greek), "intoxicate", a reference to the belief that t ...

exhibited optical activity in the visible light spectrum. He used a readily-available substitute for the amethyst. Sodium chlorate is

chiral Chirality is a property of asymmetry important in several branches of science. The word ''chirality'' is derived from the Greek (''kheir''), "hand", a familiar chiral object. An object or a system is ''chiral'' if it is distinguishable from ...

as a crystal, but in its natural (undyed) state is transparent and does not exhibit enhanced optical activity, so Perucca added an organic dye (an equilibrium

racemic mixture In chemistry, a racemic mixture, or racemate (), is one that has equal amounts of left- and right-handed enantiomers of a chiral molecule or salt. Racemic mixtures are rare in nature, but many compounds are produced industrially as racemates. ...

of a triarylmethane textile dye then known as ''extra China blue''). His goal was to see if addition of the organic dye on the crystalline structure would induce ''enhanced optical activity'' (rotation) of light in the 500-600 nm absorption band on the otherwise optically inactive dye. Perucca reported that the dyed crystal did exhibit the desired optical rotation. However, because his report was not widely distributed, his discovery of this

effect was not attributed to him, and when it was later studied by Paul Pfeiffer in Germany beginning in 1931 and reported in the literature, the effect eventually became known as the

Pfeiffer Effect The Pfeiffer effect is an optical phenomenon whereby the presence of an optically active compound influences the optical rotation of a racemic mixture of a second compound. Racemic mixtures do not rotate plane polarized light, but the equilibrium ...

. Perucca's experiment was the forerunner of another field of study which arose in the 1970s, in connection with enantioselective adsorption of racemic mixtures on inorganic crystals. This study was a basic tool in determining the origin of the

homochirality Homochirality is a uniformity of chirality, or handedness. Objects are chiral when they cannot be superposed on their mirror images. For example, the left and right hands of a human are approximately mirror images of each other but are not their ow ...

of life - scientists are still trying to determine why present earth-based life is based almost exclusively on L-enantiomers, popularly known as '' left-handed proteins''. During his tenure at the Turin Polytechnic, Perucca studied the

Volta Effect The triboelectric effect (also known as triboelectric charging) is a type of contact electrification on which certain materials become electrically charged after they are separated from a different material with which they were in contact. Rubb ...

, measuring with high precision the

electronegativity Electronegativity, symbolized as , is the tendency for an atom of a given chemical element to attract shared electrons (or electron density) when forming a chemical bond. An atom's electronegativity is affected by both its atomic number and the d ...

between pairs of dissimilar metals. He was able to establish a theoretical correlation between the Volta Effect and the

Peltier Effect The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa via a thermocouple. A thermoelectric device creates a voltage when there is a different temperature on each side. Conversely, when ...

. In 1928 he discovered that

Enrico Fermi Enrico Fermi (; 29 September 1901 – 28 November 1954) was an Italian (later naturalized American) physicist and the creator of the world's first nuclear reactor, the Chicago Pile-1. He has been called the "architect of the nuclear age" and ...

's theory on free electrons could be used to predict the constants of the

photoelectric effect The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material. Electrons emitted in this manner are called photoelectrons. The phenomenon is studied in condensed matter physics, and solid st ...

and thermionic effect in Volta's and Peltier's equations. In 1930 Perucca turned his attention to the

. He developed a new type of electric-current/voltage measuring device called the ''Elettrometro di Perucca'' which was highly sensitive.

Replication of experimental result (Nuovo Cimento)

In 2001,

University of Washington The University of Washington (UW, simply Washington, or informally U-Dub) is a public research university in Seattle, Washington. Founded in 1861, Washington is one of the oldest universities on the West Coast; it was established in Seattle a ...

chemistry professor Bart E. Kahr determined to compile a complete list of studies on crystal dyeing. He happened upon Perucca's nearly-forgotten paper. After studying and researching the subject, Kahr and associates Yonghong Bing and Werner Kaminsky repeated the experiment in 2008, using aniline blue as the dyeing compound. They did confirm the 1919 result.

Chemical & Engineering News ''Chemical & Engineering News'' (''C&EN'') is a weekly news magazine published by the American Chemical Society, providing professional and technical news and analysis in the fields of chemistry and chemical engineering.

Perucca's reputation

Perucca labored as a government employee during the

fascist Fascism is a far-right, Authoritarianism, authoritarian, ultranationalism, ultra-nationalist political Political ideology, ideology and Political movement, movement,: "extreme militaristic nationalism, contempt for electoral democracy and pol ...

regime of

Benito Mussolini Benito Amilcare Andrea Mussolini (; 29 July 188328 April 1945) was an Italian politician and journalist who founded and led the National Fascist Party. He was Prime Minister of Italy from the March on Rome in 1922 until his deposition in 194 ...

. However, his associates remember him as strongly anti-fascist, not a safe viewpoint in those days. In 1939 Perucca received Mussolini during an official visit to

Turin Turin ( , Piedmontese language, Piedmontese: ; it, Torino ) is a city and an important business and cultural centre in Northern Italy. It is the capital city of Piedmont and of the Metropolitan City of Turin, and was the first Italian capital ...

. Rather than donning the black attire which the Duce's supporters affected in his presence, Perucca made "a bold political statement" by wearing fancy ceremonial attire to the meeting. Perucca once demanded that a student describe the

Carnot Cycle A Carnot cycle is an ideal thermodynamic cycle proposed by French physicist Sadi Carnot in 1824 and expanded upon by others in the 1830s and 1840s. By Carnot's theorem, it provides an upper limit on the efficiency of any classical thermodynam ...

during an oral examination. The flustered student was unable to comply, so the professor directed him to draw a circle on the blackboard. He then directed him to draw another circle of equal size nearby. He then said the student had drawn a "Carnot bicycle", that he should get on and ride away, because he had failed the exam. Perucca once asked a chemistry student why the laboratory's washbasins were located one meter above the laboratory's floor. The confused student stumbled through possibilities such as necessary hydraulic force or sanitary requirements. But Perucca failed the already demoralized student and explained that the basins were so located in order to allow the workers to wash their hands while standing up.

References

{{DEFAULTSORT:Perucca, Eligio Italian chemists People from Potenza Scientists from Turin 1965 deaths 1890 births Academic staff of the Polytechnic University of Turin