Stanislao Cannizzaro

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Stanislao Cannizzaro

Stanislao Cannizzaro (born July 13, 1826 in Palermo , † May 10, 1910 in Rome ) was an Italian chemist and politician. Cannizzaro clarified the difference between atomic and molecular weight . He recognized that hydrogen gas exists as a molecule and helped chemistry to come up with correct empirical formulas . He found a method for preparing carboxylic acids and alcohols from the corresponding aldehydes and investigated the photochemistry of santonin .

Cannizzaro supported the Italian unification movement and Garibaldi's uprising in Sicily . For a short time he was a member of the Sicilian government. He led the expansion of the chemistry department at the University of Palermo. He was later made a senator and moved to Rome.

His scientific school shaped generations of chemists in Italy and produced numerous industrial chemists and later professors. Well-known students were Raffaello Nasini , Francesco Mauro , Augusto Piccini and Emanuele Paternò , with whom he founded the specialist magazine Gazzetta Chimica Italiana .

life and work

Cannizzaro was born in Palermo in 1826 as the son of the Magistrate Mariano Cannizzaro, who was General Director of the Police in Sicily from 1826, and Anna Di Benedetto. As the youngest of ten children in the family, she studied grammar, rhetoric, poetry, philosophy, mathematics and geography in a high school and received an award in mathematics at the age of 15. In a cholera epicenter in 1837 he lost two brothers and infected himself. Cannizzaro studied medicine in Palermo between 1841 and 1845; by the age of 19 he had already published three scientific papers. In 1845 he became an assistant in Pisa to Raffaele Piria , who had isolated salicylic acid , a pain-relieving component of willow bark. He was a close friend of Cesare Bertagnini , another assistant to Piria, who had discovered the reaction of aldehydes with alkali sulfite.

In 1847 Cannizzaro took part in Garibaldi's uprising to unite Italy. He became an artillery officer and the movement's youngest MP. The uprising was put down and Cannizzaro fled to Marseille , since he was sentenced to death in absentia in Messina in 1849 . He spent three years in Paris and continued his chemical education in Eugène Chevreul's laboratory . In Paris, Canizzarro worked with Cloez on the synthesis of cyanamide . In 1851 he returned to Italy, first he got a job as a professor in Alessandria .

In 1851 he became professor of physical chemistry at the Collegio Nazionale in Alessandria. At the Bertagninis house in Pisa, he found that the reaction of benzaldehyde in an alkaline medium produced benzyl alcohol and benzoic acid . This reaction got its name, the Cannizzaro reaction . Part of the benzaldehyde is reduced (to benzyl alcohol) the other part is oxidized (to benzoic acid). He was able to obtain the first aromatic primary alcohol by distilling the benzyl alcohol. His work was published in Liebig's Annalen in 1853.

Cannizzaro brought about a standardization of the then incomprehensible relationships between atom and molecule and resorted to Avogadro's law. His students such as Nasini and Paternò devoted a large part of their research to determining the molecular weight of substances, for example using the cryoscopy developed by François Marie Raoult . He was professor at the universities of Genoa (1855), Palermo (1861–1871) and finally from 1871 in Rome . In Rome, Cannizzaro studied various natural substances , in particular santonin . In 1871 he was appointed senator .

Working on atomic weight

Cannizzaro's importance was groundbreaking through a clear definition of atomic weight and molecular weight. The Italian physicist Amedeo Avogadro had already published the hypothesis in 1811 that equal volumes of any gas contain the same number of particles under identical pressure and temperature conditions (see Avogadro's law and Avogadro's constant ). Avogadro differentiated between atoms (molécules élémentaires) and molecules (molécules intégrantes) for particles in the gas phase and assumed that atoms in the gas phase do not exist individually but as paired atoms. These ideas had long been forgotten.

The influential chemist Jöns Jakob Berzelius introduced the concept of the atom. Instead of the concept of elementary molecules coined by Avogadro, he put the concept of the atom. However, the name exchange created a source of later confusion. For him, the atom was an elementary and unbound particle. For elementary gases such as hydrogen, this means that they are also present unbound in the gas space. According to Berzelius' molecular theory, molecules were divisible substances, so that at that time a wrong idea about molecules and atoms in the gas space was formed. The reference point for the atomic weights also added to the confusion; Oxygen became the reference point and was given an arbitrary atomic weight of 100.

Charles Frédéric Gerhardt found in 1842 when determining the gas densities of organic compounds that there were difficulties with the determination of the molecular size. According to this, one equivalent of water would have to have the empirical formula H 4 O 2 and the formula C 2 O 4 or the molecular size would have to be halved to the carbon dioxide . Gerhardt suggested dividing the molecular size so that the carbon got the equivalent weight of 12, the oxygen the value 16, the sulfur the value 32. Gerhardt had not yet differentiated atomic and molecular weights by using equivalent weights. He still assumed that a molecule of a uniform gas, a substance, was not divisible. Gerhardt said that certain molecules (or atoms) can take up 1, 2, 4 parts by volume. For oxides, the situation became even more complicated, since several atomic weights were possible for the same element in different compounds. Gerhardt's theses led to incorrect atomic weights in metals, so that many other chemists rejected Gerhardt's theses.

Had great significance for modern molecular theory, the representation of the organometallic compound diethylzinc by Edward Frankland . The gas density and chemical composition of diethyl zinc have been carefully studied by Cannizaro. According to Cannizzaro's considerations, zinc had to be given an atomic weight that was twice as high as Gerhardt had previously assumed. Hydrogen gas had to be a molecule made up of two atoms, each hydrogen atom had to have an atomic mass of 1. The ethyl group in zinc ethyl had to appear twice in the gaseous molecule.

Chemists' Congress in Karlsruhe in 1860

In 1860 August Kekulé invited all well-known chemists in the world to a congress in Karlsruhe to make Cannizzaro's ideas about atomic weight known. At the chemists' congress in Karlsruhe in 1860 , the chemists present were given a clear briefing by Cannizzaro. His work Sunto di un corso di filosofia chimica (English: summary of a course in chemical philosophy ), written in the form of a letter to Sebastiano de Luca in 1858, when Cannizzaro was professor of chemistry at the University of Genoa, gave an overview of a Teaching program based on fundamental conclusions based on atomic theory. Cannizzaro's publication drew the attention of many chemists present to the work of Avogadro and ensured a unified and consistent system of formulas and atomic, equivalent and molecular weights.

The congress participants voted for the new form of atomic weight. The founders of the periodic table Lothar Meyer and Dmitri Iwanowitsch Mendeleev visited the congress and received important suggestions for the development of the periodic table. Cannizzaro was then offered several professorships at various universities. However, he chose Palermo, his hometown.

Awards and honors

For the method he discovered to determine the atomic weights from the specific heat of volatile substances, he received the Copley Medal of the British Royal Society . He was its external member since 1889.

In 1864 he became a member of the Accademia dei XL , in 1871 he was appointed senator , from 1873 he was a full member of the Accademia dei Lincei in Rome, from 1888 a corresponding member of the Prussian Academy of Sciences and from 1889 a foreign member of the Bavarian Academy of Sciences . In 1889 he was accepted as a corresponding member of the Russian Academy of Sciences in Saint Petersburg and in 1894 of the Académie des Sciences in Paris. In 1897 he became an Honorary Fellow of the Royal Society of Edinburgh . In 1926 the Società chimica italiana held a centenary celebration.

Scientific high schools in Palermo, Vittoria and Rome are named after him. The 1924 by Ferruccio Zambonini , Ottorino De Fiore and Guido Carobbi first described mineral Cannizzarit was named after him. In 1970 the lunar crater Cannizzaro was named after him. The Società Chimica Italiana awards the Medaglia d´Oro Stanislao Cannizzaro in honor of Cannizzaro . The European Chemical Society ranks Cannizzaro among the 100 most respected European chemists.

literature

  • Henry M. Leicester: Cannizzaro, Stanislao . In: Charles Coulston Gillispie (Ed.): Dictionary of Scientific Biography . tape 3 : Pierre Cabanis - Heinrich von Dechen . Charles Scribner's Sons, New York 1971, p. 45-49 .
  • Günther Bugge (ed.): The book of the great chemists. Volume 2: From Liebig to Arrhenius. Verlag Chemie, Weinheim et al. 1930, pp. 173 ff. (Reprint. Ibid 1974, ISBN 3-527-25021-2 ).
  • Aldo Gaudiano - Domenico Marotta:  Cannizzaro, Stanislao. In: Alberto M. Ghisalberti (Ed.): Dizionario Biografico degli Italiani (DBI). Volume 18:  Canella – Cappello. Istituto della Enciclopedia Italiana, Rome 1975.
  • Stanislao Cannizzaro: Outline of a course in theoretical chemistry (1858). Translated by Arthur Miolati, edited by Lothar Meyer. Ostwalds Klassiker 30, Leipzig: Engelmann 1891, Archive
  • Cannizzaro: Sketch of a course in chemical philosophy , Edinburgh 1947
  • J. Bradley: Before and after Cannizzaro , Caithness: Wittles 1992

Web links

Individual evidence

  1. ^ Heinz D. Roth: A tribute to Stanislao Cannizzaro, chemical informationist and photochemist. In: Photochemical & Photobiological Sciences . 10, 2011, pp. 1849-1853, doi: 10.1039 / c1pp05217a .
  2. ↑ Albert Gossauer: Structure and reactivity of biomolecules. An introduction to organic chemistry. Verlag Helvetica Chimica Acta et al., Zurich 2006, ISBN 3-906390-29-2 , p. 290.
  3. ↑ Antonio di Meo: "Le vecchie molecular, i vecchi atomi": l'ultima battaglia di Stanislao Cannizzaro e la nascita della chimica fisica. In: Atti del XI Convegno nazionale di storia e fondamenti della chimica , pp. 299-329, 2005.
  4. ^ MH Sainte-Claire Deville, S. Cannizzaro: Della disassociazione ossia scomposizione dei corpi sotto l'influenza del calore ;. In: Il Nuovo Cimento . 6, 1857, pp. 428-430, doi: 10.1007 / BF02726982 .
  5. ↑ C. Graebe: The course of development of Avogadro's theory. In: Journal for Practical Chemistry. 87, 1912, pp. 145-208, doi: 10.1002 / prac.19130870112 .
  6. ^ Entry on Cannizzaro; Stanislao (1826-1910) in the Archives of the Royal Society , London
  7. ^ Members of the previous academies. Stanislao Cannizzaro. Berlin-Brandenburg Academy of Sciences and Humanities , accessed on March 5, 2015 .
  8. ^ Member entry of Stanislao Cannizzaro at the Bavarian Academy of Sciences , accessed on January 12, 2017.
  9. ^ Foreign members of the Russian Academy of Sciences since 1724. Stanislao Cannizzaro. Russian Academy of Sciences, accessed September 3, 2015 .
  10. ^ List of members since 1666: Letter C. Académie des sciences, accessed on October 25, 2019 (French).
  11. ^ Fellows Directory. Biographical Index: Former RSE Fellows 1783–2002. Royal Society of Edinburgh, accessed October 16, 2019 .
  12. ^ The documents of Cannizzaro at the Italian Chemical Society ( ital. ).
  13. ^ Website of the Liceo Cannizzaro in Vittoria .
  14. ^ Website of the Liceo Cannizzaro in Palermo .
  15. ^ Website of the Liceo Cannizzaro in Rome .
  16. ↑ Marco E. Ciriotti, Lorenza Fascio, Marco Pasero: Italian Type Minerals . 1st edition. Edizioni Plus - Università di Pisa, Pisa 2009, ISBN 978-88-8492-592-3 , p. 64 .
  17. ↑ Cannizzarite . In: John W. Anthony, Richard A. Bideaux, Kenneth W. Bladh, Monte C. Nichols (Eds.): Handbook of Mineralogy, Mineralogical Society of America . 2001 ( handbookofmineralogy.org [PDF; 64 kB ; accessed on June 18, 2018]).
  18. ^ Gazetteer of Planetary Nomenclature
  19. ^ List of the winners of the Medaglia d´Oro Stanislao Cannizzaro .
  20. ^ List of the 100 most respected European chemists of the FECS.


personal data
SURNAME Cannizzaro, Stanislao
BRIEF DESCRIPTION Italian chemist
DATE OF BIRTH July 13, 1826
PLACE OF BIRTH Palermo
DATE OF DEATH May 10, 1910
Place of death Rome