Cossa, Alfonso

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(b. Milan, Italy, 3 November 1833; d. Turin, Italy, 23 October 1902).

Chemistery, mineralogy.

Alfonso Cossa was the son of Giuseppe Cossa. librarian of Milan’s famous Bibliotecadi Brera and an authority on paleography and diplomacy, and his wife. Maria Bagnacavallo. After completing his classical studies in Milan, in 1852 Alfonso was sent to Pavia, where he studied at the Collegio Borromeo. In November 1857 he received the M.D. degree from the University of Pavia with a dissertation on the history of electrochemistry. Before receiving his degree he had translated into Italian two books by Justus Liebig: Die Grundsätze der Agricultur-Chemie mit Rücksicht auf die in England angestellten Untersuchungen (1855) and Zur Theorie und Praxis in der Landwirtschaft (1856), He married Giovanna Panizza; they had two daughters, Maria and Eugenia.

Cossa was one of those rare scholars who enter fields for which they have no formal training. After his education as a physician, he successively became a botanist, an agricultural and plant chemist, a mineralogical chemist, and an inorganic and coordination chemist. When mineralogical chemistry, his favorite branch of chemistry, underwent a number of changes as a result of new physicochemical theories, Cossa, although a mature scholar with a substantial reputation, did not hesitate to return to school, along with his students, to learn from his colleagues and friends the mathematical ideas that are essential to modern chemistry. This continual intellectual development was characteristic of Cossa throughout his life.

From an early age Cossa demonstrated a striking predilection for chemistry, especially applied chemistry. He possessed unusual scientific and didactic talents, but at the beginning of his career his interests did not exhibit a precise trend, and he was forced to learn much on his own. In the mid-nineteenth century most university positions in Italy were occupied by men whose teaching was purely theoretical, with no experimental content or practical application, and who failed to consider the great progress in chemistry that was being made in other countries. In short, the teaching of chemistry in Italy was comparable with that in other countries sixty years earlier.

At the time Cossa received his medical degree, there was a great shortage of teachers in Italy, He therefore remained at the University of Pavia, where, despite his lack of specialized training, he was assistente di medicina legalee polizia medica (1857–1860). In May 1860 he was appointed assistente stabile dichimica generate, and later that year he was named farmacista. He remained at the university as professor of chemistry and director of the Technical Institute (1861–1866), where his outstanding abilities as a researcher and teacher were recognized by Quintino Sella, the statesman and crystallographer who helped place the new national government on a firm footing after the unification of Italy. In 1866, when Venice was united to the newly formed kingdom of Italy, Sella commissioned Cossa to organize and found a technical institute at Udine, where he remained until 1871 as professor of chemistry and director.

After a short stay (1871–1873) at the Royal High School of Agriculture at Portici, in 1873 Cossa was appointed director of the agricultural station and teacher of general and mining chemistry at the Royal Industrial Museum, both in Turin. In 1882 he succeeded Ascanio Sobrero, the discoverer of nitroglycerin, as professor of assaying and mining chemistry at Turin’s Royal School of Applied Engineering, of which he was director from 1887 to 1902.

Cossa was a member of the Turin Academy of Sciences (elected 1871, president 1901–1902), the Accademia dei Lincei, the Berlin Academy of Sciences, the Mineralogical Society of St. Petersburg, and other Italian and foreign societies.

The subject of Cossa’s early works was largely agricultural and plant chemistry. He worked on absorption by roots, the chemistry of plant seeds, sugarcane, plant respiration, soils, water supplies, manures, sugar-beet roots, grape must, ash of lemon leaves and fruit, vetches, the action of sulfur on calcium carbonate, and the decomposition of chlorophyll by the light of burning magnesium. Like Pasteur, Cossa was interested in wine making, and he proposed several methods for destroying the plant lice (Phylloxera) that attack the roots and leaves of grapevines. From 1872 to 1882 he was editor of the journal Le stazioni sperimentali agrarie italiane, which he founded and published in Turin. He also carried out a number of studies in medical-legal chemistry, especially on alkaloids such as veratrine. He suggested the use of dialysis for the detection of poisonous alkaloids.

Among Cossa’s researches in inorganic chemistry, carried out between 1867 and 1892, were work on magnesium, ozonomerry, and sulfur; one of the first observations of the behavior of aluminum in contact with metallic solutions, which helped to establish the position of aluminum in the electrochemical series; studies of aluminum amalgam; the first synthesis of hydrogen sulfide; work on boron; work on vanadium; and studies of the action of nitric acid on zinc.

Cossa’s friendship with Quintino Sella and Bartolomeo Gastaldi led him to devote himself to mineralogical chemistry and petrography. Throughout his career the former was Cossa’s primary field of interest, with almost half of his works being devoted to this subject. Although petrography was already flourishing in Germany, largely as a result of the efforts of Ferdinand Zirkel and Harry Rosenbusch. Cossa apparently was the first person in Italy to pursue such studies. On Cossa’s urging, in 1889 the Italian government established in Rome, as part of the Royal Geological Office, a petrographic laboratory directed by Ettore Mattirolo, an engineer who was a former student and collaborator of Cossa’s.

Cossa classified, characterized the properties, determined the compositions, and proposed mineralogical formulas for a variety of minerals and rocks, not only from Italy but also from many other sources. One of the minerals that he studied, a variety of paragonite—a sodium mica of composition H2NaAl3 (SiO4)3—was named cossaite in his honor. Cossa went beyond microscopic investigations and analyses of minerals; he also prepared artificial minerals.

Closely related to his mineralogical studies were Cossa’s investigations of lanthanum, cerium, and didymium. He found these elements to be widely distributed in nature, not only in many rocks but also in bones; ashes of rice, tobacco, beech trees, and other plants; and human urine. Because the knowledge of the chemistry and nature of the rare earths was obscure at the time, some of Cossa’s interpretations of his data, particularly with respect to oxidation states, were incorrect; but his observations and data are still valid today.

Long interested in biography and the history to chemistry. Cossa wrote articles on the lives and work of a number of chemists. Of these the most important was his study of Angelo Sala (1576–1637). who was one of the first chemists to describe fermentation; in his emphasis on experimentation, Sala was a true precursor of Joseph Black, Joseph Priestley, and Carl Wilhelm Scheele. Cossa’s study of his friend Quintino Sella led him to a new field of research. In 1885 the Accademia dei Lincei asked Cossa to commemorate the life and work of Sella, who had died the year before. In the course of his bibliographical research, Cossa found Sella’s Sulle forme di alcuni sali di platino a base di platinodiamina (1856–1857) and decided to carry out experimental studies on platinum-ammine compounds. Beginning in 1885 and continuing until 1897, he made a long series of investigations—his most important chemical contributions. Although Cossa interpreted his data in terms of the now obsolete Blomstrand-Jørgensen chain theory and named his compounds according to Per Cleve’s obsolete nomenclature system, these practices in no way invalidate his experimental results.

In attempting to reconcile some discrepancies between the work of Jules Reiset and Cleve. Cossa discovered a fifth isomer of Magnus’s green salt, [Pt(NH3)4][PtC14], which he formulated as Pt(NH3)4Cl2 · PtCl2. He formulated the new yellow isomer [Pt NH34][PtCl3 (NH3]2 as 2 PtCl.NH3Cl) · Pt(NH3)4Cl2 that is, he regarded it as a compound of one molecule of platosodiammine chloride, (Pt(NH3)4Cl2—modern [Pt(NH3)4Cl2—and two molecules of the chloride of a new base, which he called platosemiammine (PtCl · NH3Cl2). The orangered “potassiochloride” of this new base is now known as Cossa’s first salt, K[PtCl3 (NH3)] · H2O.

By oxidizing K[PtCl3 (NH3)] · H2O. Cossa also obtained the corresponding yellow platinum (IV) salt, K[PtCl5 (NH3) · H2O, now known as Cossa’s second salt, which he called platinosemiammine potassium chloride and formulated as Pt(NH3)Cl4 · KCl. Cossa also confirmed his view that one atom of platinum (II) could combine with one molecule of a base to form compounds containing pyridine (py; C5H5N) and ethylamine analogous to his monoammine compounds.

The Scottish chemist Thomas Anderson found that when solutions of (pyH)2[PtCl6] and the corresponding compounds of pyridine derivatives are boiled, hydrogen chloride is released with formation of cis-[PtCl4py2] (Anderson’s platinic compound) or the corresponding compounds of pyridine derivatives, a reaction known as Anderson’s reaction.


I. Original Works. Cossa wrote several books and about 130 articles, many of which were published separately as well as in Italian journals such as Gazzetta chimica italiana, Atti della Reale Accademia delle scienze, Torino, Stazioni sperimentali agrarie italiane, Atti della Reale accademia dei Lincei, and Ricerche chimiche. An almost complete bibliography to Cossa’s works is found in In Memoria di Alfonso Cossanel primo anniversario della sua morte (Turin, 1903), 91–108. His most important article on platinum ammines, describing Cossa’s first and second salts, is “Sopraannuovoisomero del sale verde del Magnus,” in Gazzetta chimicaitaliana. 20 (1890) 725–753. translated in Berichteder Deutschen chemischen Gesellschaft, 23 (1890), 2503–2509.

A number of Cossa’s petrographic and mineralogical works on Italian rocks and minerals were published in Ricerche chimiche e microscophiche suroccie e mineralid’Italia (Turin, 1881), The collection of thousands of these specimens, ordered and classified by Cossa, is now housed in the School of Applied Engineering at Turin.

II. Secondary Literature.In Memoria di Alfonso Cossa nel primo anniversario della sua morte, cited above prints several earlier obituaries (pages in parentheses denote the pages in this book): Luigi Gabba. in Annali della Societa chimica di Milano. 8 (1902), 184ff. (37–43); Icilio Guaresehi. in Memorie della Reale Accademia delle seienze, Torino. 2nd ser., 53 (1903), 79–92 (58–79): Augusto Piccini. in Rendiconti della Reale Accademia dei Lincei Classe di scienze fisiche, matematiche, e natural, 11 . no, 2 (1902), 235ff. (33–37): and M. Zecchini, in La chimica industriale, 4 . no, 21 (1902). 321–322 (44–52). The only article in English is George B. Kauffman and Ester Molayem, “Alfonso Cossa (1833–1902), a Self-Taught Italian Chemist,” in Ambix, submitted for publication.

George B. Kauffman

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Cossa, Alfonso

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