Born in Karlsbad, a town in the Austrian Empire (now Karlovy Vary, Czech Republic), Loschmidt became professor of physical chemistry at the University of Vienna in 1868.

The first was Bohemian priest Adalbert Czech, who persuaded Loschmidt's parents to send young Josef to high school in the Piarist monastery in Schlackenwerth and, in 1837, to advanced high-school classes in Prague.

[1] His 1861 booklet, Chemische Studien ("chemical studies"), proposed two-dimensional representations for over 300 molecules in a style remarkably similar to that used by modern chemists.

This latter quantity is now known as the Loschmidt constant in his honour, and its modern value is 2.65×1019 molecules per cubic centimetre at standard temperature and pressure (STP).

It led Boltzmann to his statistical concept of entropy as a logarithmic tally of the number of microstates corresponding to a given thermodynamic state.