Eligio Perucca

Eligio Perucca (?? - 1965) was an Italian Physics instructor and researcher at the University of Turin 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 in 1919, but his contribution was overlooked and forgotten until recently.

cientific Achievements

In a paper published in 1919, ["Nuovo Cimento", 1919, 18, 112] , Perucca reported an experiment which produced optical rotatory dispersion (ORD) as a result of passing linearly polarized light thru colored crystals of sodium chlorate. Perucca was attempting to replicate a nineteenth-century experiment (1860) in which amethyst exhibited optical activity in the visible light spectrum. He used a readily-available substitute for the amethyst. Sodium chlorate is chiral 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 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 stereochemistry 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 [Paul Pfeiffer & Kurt Quehl (1932), "Aktivierung von Komplexsalzen in wäßriger Lösung", Chemische Berichte 65, 560-565] , the effect eventually became known as the Pfeiffer Effect.

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 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".

Replication of experimental result

In 2001, University of Washington chemistry professor Bart E. Kahr determined to compile a complete list of studies on crystal dyeing [ "Chemical Reviews" 2001, 101, 893] . 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, Vol. 86 No. 33, 18 August 2008, p. 38, "Recognizing a Pioneer"] Kahr stated:

"Perucca's paper should be viewed as a milestone in the chiroptics literature, as well as in the history of enantioselective chemistry."

Perucca's reputation

Perucca labored as a government employee during the fascist regime of Benito Mussolini. 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. 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 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 thru 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.

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