Abstract Giuseppe Bruni, a pioneer in the development of structural chemistry and the chemistry of solid solutions and isomorphism, and also outstanding for his researches in the chemistry and technology of rubber, was born in Parma, Italy, in 1873, and died in Milan in 1946. The news of Bruni's passing did not, for some unexplained reason, become known to most of his many friends and admirers abroad until the end of 1949. After graduating in Parma in 1896, he joined the renowned Ciamician at Bologna University, where for nearly ten years he worked mainly on the nature and theory of solid solutions and of isomorphism. In 1908, he summed up his researches in this field in a monograph entitled “Solid Solutions and Isomorphism,” published in Germany under the title “Feste Lösungen und Isomorphismus.” He temporarily left Bologna to work with van't Hoff in 1900–1901, and the latter subsequently emphasized the importance of Bruni's researches in the following words: “Ce savant à contribué d'une partie prépondérante à l'adoption des lois sur les solutions solides et les mélanges isomorphes, qui, sans son intervention auraient été troublée par des notions confuses.” [This scholar and master has contributed in a major way to the establishment of the laws of solid solutions and of isomorphic mixtures, for without the part which he played, the formulation of these laws would have been beset by a confusion of ideas.] The year 1907 saw Bruni appointed to the Chair of General and Inorganic Chemistry at Padua, where for a decade he conducted researches on diffusion in the solid state, on the cryoscopic method, etc. In 1917 he was appointed Professor of General and Inorganic Chemistry at the Polytechnic School of Milan—an institution similar in character to the Massachusetts Institute of Technology. He held this post until shortly before his death. In the following, a brief résumé is given of his work in rubber science and technology.