French chemist (1800–1884) best known for his work in determining atomic and molecular weights. ALS in French, signed “J. Dumas,” one page, 5.25 x 8, no date. Untranslated letter to an unidentified gentleman. Central horizontal and vertical fold, light purple pencil notations to top and bottom, small ink spot to signature, and some light toning, otherwise fine condition. RRAuction COA.