Vauquelin and Fourcroy taught him, and helped him get a post as Gay-Lussac’s demonstrator at the École Polytechnique, the start of a lifelong friendship and professional relationship; both Gay-Lussac and Biot did important collaborative work with Thénard. He queried Berthollet’s views on oxides; Berthollet invited him to join his Société d’Arcueil. With Chaptal, he co-founded La SEIN, an influential Society for the Encouragement of Industry; Chaptal’s demands also led him to develop the pigment cobalt blue. Wöhler (whose collaborator Liebig had studied with Thénard) wrote excitedly to Berzelius about meeting him on a visit to Paris.