(b. Rome, Italy, 17 December 1880; d. Naples, Italy, 12 January 1932)
Zambonini was the son of Ersilia Zuccari and Gustavo Zambonini di Montebugnoli, descended from a noble Bolognese family reduced to near poverty by financial misfortunes. Obliged to work in order to continue his studies after his father’s death, Ferruccio gave private lessons and copied documents for lawyers. His first scientific works were published in 1898, while he was still a student. Zambonini graduated in natural sciences from the University of Rome in 1903 and immediately became assistant in chemistry at the Turin Polytechnic, where he acquired a considerable knowledge of general analytical chemistry. In 1906 he worked at the University of Naples with Arcgelo Scacchi, the leading Italian mineralogist of the nineteenth century .
Zambonini became professor at the University of Sassari in 1909 ; in 1911 he moved to Palermo, and two years later to Turin. In 1923 he obtained the chair of general chemistry at the University of Naples, where he continued his mineralogical and chemical studies, and was twice elected vice-chancellor of the university.
Zambonini was the leading mineralogist in Italy during the first half of the twentieth century, a worthy successor of Scacchi and Quintino Sella. He contributed substantially to the knowledge of many minerals; one of his most important works, fundamental to the study of volcanic products, is “Mi-neralogia vesuviana” (1910), a collection of data on more than 250 minerals from Vesuvius and Monte Somma, with Zambonini’s own minutely detailed descriptions and commentary. This work won him the annual award of the Royal Academy of Sciences of Naples. An appendix appeared in 1912 ; and in 1935, after his death, Emanuele Quercigh compiled a second edition that included all the new minerals discovered by Zambonini and his students during the last the years of his life.
Zambonini extended knowledge of the dehydration of minerals by studying the role of water in hydrated silicates, especially zeolites, and interpreting it in the light of the most advanced theories of colloidal chemistry.
In general mineralogy, Zambonini’s isomorphism anticipated modern theories of crystal chemistry. In the important “Sulle soluzioni solide dei composti di calcio…” he demonstrated that the rare earths in trivalent rare-earth compounds could be replaced with alkaline earths and lead. He also studied their solubility limits in the solid state and applied the results to simplifying and clarifying the formulas of many minerals.
Zambonini gave a very interesting explanation of the concomitant replacement, in plagioclase, of part of the calcium by sodium, and silicon by aluminum. He attributed this substitution to the closeness of the ionic radii of sodium and calcium, and of aluminum and silicon. In Italy the possibility of isomorphism between ions of similar radii is called Zambonini’s rule, thus indicating that the solid-state substitution of elements is a function of ionic radii, rather than of chemical properties.
Zambonini conducted pioneering research on the mixed crystals of the epidote-clinozoisite series. Through chemical analyses and a study of optical properties of the series, he discovered the existence of mixed stereoisomeric crystals, which have the same chemical composition but optical properties that vary according to whether it is the free aluminum or the aluminum bound to hydroxyls that is replaced by ferric iron.
While working on mixed crystals of molybdates and tungstates of calcium, barium, strontium, and lead, along with the analogous compounds of rare earths, Zambonini noticed that their angular values and optical properties did not vary regularly with the variation in composition of the mixed crystals; there are values not included among those of the two components. He observed the same phenomenon in pairs of artificial compounds and concluded that there are important exceptions to the principle that the optical properties of mixed crystals vary regularly with their composition. In 1922 Zambonini discovered the isomorphism between potassium fluoborate and permanganate, two compounds that are similar neither in their chemical composition nor even in the sum of their valences.
In 1924 Zambonini was one of the first to apply Bohr’s atomic theory in order to explain the iso-morphism of the trivalent rare earths with alkaline earths and with lead. Similarly, in 1911 he had been an innovator when he used the amount of lead and uranium in some minerals to date rocks, thus anticipating modern methods. For the calculations he used Rayleigh’s formula.
In the last decade of his active life Zambonini contributed substantially to the chemistry of the rare earths. With collaborators he studied an isotherm of the binary systems of rare-earth sulfates and alkaline sulfates. He had obtained the lantha-nides for this research through a long and difficult process of fractionation, carried out with very limited means at the Institute of Mineralogy in Turin.
For his scientific achievements Zambonini was elected a member of the Accademia Nazionale dei Lincei, the Royal Academy of Physical and Mathematical Sciences of Naples, the Academy of Sciences of Turin, and the Accademia dei Quaranta. He was president of the Geological Society of Italy, vice-chancellor of the University of Naples, and editor of Zeitschrift fur Kristallographie, Kris-tallgeometrie, Kris tallphysik, Kristallchemie, and was awarded the Wilde Prize of the Institut de France.
A comprehensive bibliography of Zambonini’s writings (162 works) is included with F. Giordani, “Comme-morazione di Ferruccio Zambonini” in Rendiconti dell’ Accademia delle scienze fisiche matematiche, 4th ser., 3 (1933), 8-19, with portrait, “Mineralogia Vesuviana” was published as Atti dell’ Accademia delle scienze fisiche e matematiche, 2nd ser., 14 no. 6 (1910); 2nd ed., compiled by E. Quercigh, ibid., supp. 20 (1935). “Sulle soluzioni solide dei composti de calcio, stronzio, bario e piombo con quelli delle “terre rare” …,” appeared in Rivista italiana di mineralogia,45 (1915), 1-185.