Summary Data are presented on the anhydrides of dibasic acids COOH (CH2).-COOH where n is 4, 5, 6, 7, 8, 9, 10, 11, 12 and 16. The anhydrides are all linear polymers and when heated in a molecular still they are depolymerized yielding volatile products (,% anhydrides). The latter are either cyclic monomers or dimers depending upon the unit length, n+ 3. The compounds thus obtained are rings of 7, 8, 18 (dimeric), 10, 22 (dimeric), ...