He also collaborated with Julius Oppert.
He collaborated with his father in the great edition of Saadia and the edition of Abu-1Walid, and also produced a number of important editions of other Arabic writers.
With Lord Kelvin he collaborated in writing the well-known Treatise on Natural Philosophy.
Arnault collaborated in a Vie politique et militaire de Napoleon (1822), and wrote some very interesting Souvenirs d'un sexagenaire (1833), which contain much out-of-the-way information about the history of the years previous to 1804.
His philosophical works include annotations to Garve's translation of the Politics of Aristotle (1799-1800), and a large share in the Beitrage zur Geschichte der Philosophie (published in twelve parts between 1791 and 1799), in which he collaborated with Forberg, Reinhold and Niethammer.