[2] In 1904 he obtained a degree in chemistry, followed by six months of study at the University of Leipzig, attending the lectures of the chemist Wilhelm Ostwald.

[3] Police records, however, showed that Mieli's homosexuality, referred to as 'manifest immorality' was well known in the local area, which would have severely inhibited his political career.

[2][1] His history of science career began whilst a chemistry lecturer in Rome, building on interest stimulated in his studies in Germany.

[2] He worked at the Universidad Nacional del Litoral in Santa Fé, from 1940 to 1943 where he founded an Institute for the History and Philosophy of Science and continued to edit Archeion.

Following the 1943 Argentine coup d'état and the new Government's intervention in the university, his employment contract was cancelled,[2] and he retired to Florida, near Buenos Aires.

[1] In poor health, and without the financial backing of the university, he ceased being editor of Archeion, which was subsequently relaunched as Archives internationales d'histoire des sciences.

[8] Hirschfield and Mieli had both been members of the organizing committee of the first Congress of Sexology, in Berlin, held earlier that year in 1921.

He considered homosexuality a "completely natural fact, not something to cure but to be analysed with a high degree of objectivity", which Benadusi notes was an "absolute novelty".