At first his work appeared as that of his master and patron Fourcroy, then in their joint names; in 1790 he began to publish on his own, and between that year and 1833 his name is associated with 376 papers. Most of these were simple records of patient and laborious analytical operations, and it is perhaps surprising that among all the substances he analysed he detected only two new elements, beryllium in 1798 in beryl and chromium in 1797 in a red lead ore from Siberia. He also managed to get liquid ammonia at atmospheric pressure.
Later with Fourcroy, he identified a metal in a platinum residue they called ‘ptène’, This name ‘ptene’ or ‘ptène’ was reported as an early synonym for osmium.
Either together or successively he held the offices of inspector of mines, professor at the School of Mines and at the Polytechnic School, assayer of gold and silver articles, professor of chemistry in the College de France and at the Jardin des Plantes, member of the Council of Industry and Commerce, commissioner on the pharmacy laws, and finally professor of chemistry to the Medical Faculty, to which he succeeded on Fourcroy's death in 1809. His lectures, which were supplemented with practical laboratory teaching, were attended by many chemists who subsequently attained distinction.
A lesser-known contribution and finding of his included the study of hens fed a known amount of mineral.  "Having calculated all the lime in oats fed to a hen, found still more in the shells of its eggs.  Therefore, there is a creation of matter.  In what way, no one knows."