[2] Moving to Paris, he became a laboratory assistant at the Jardin du Roi and was befriended by a professor of chemistry.

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.

[4] 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.

In 1806, working with asparagus, he and Pierre Jean Robiquet (future discoverer of the famous red dye alizarin, then a young chemist and his assistant) isolated the amino acid asparagine, the first one to be discovered.