CHEMISTS. 7 letters. Eugène CHEVREUL (Muséum letterhead), Jean-Baptiste DUMAS (3, as Minister of Agriculture and Commerce), Henri SAINTE-CLAIRE DEVILLE (2, one on the letterhead of the Chemistry Laboratory of the ENS, the other about tests for a process for making medals), Baron THÉNARD (1824). Enclosed are 2 early 19th-century manuscripts, in unidentified hands, one entitled "Purification du Rhodium" (½ p. in-4), the other of 9 pp. in-4 numbered 5 to 8 (incomplete from beginning) and formerly attributed to Silvestre de Sacy: notes on metals and chemical elements: chromium, columbium, titanium, uranium, cerium, tellurium, bismuth, etc.