[1] Angeli studied in Padua, where he met the chemist Giacomo Luigi Ciamician.
In 1894, he worked briefly in Munich with Adolf von Baeyer, learning medicinal chemistry.
In 1915, he became Professor of Organic Chemistry at the University of Florence (Istituto di Studi Superiori), a position that was created specifically for him.
He investigated the structure of hydrazoic acid, synthesised nitrohydroxylamine (1894), and discovered the nitroxyl radical.
The Angeli-Rimini reaction (1896) for the detection of aldehydes was named after him and his student Enrico Rimini.