It was subsequently pointed out by Buchner and Meisenheimer [1904] that Baeyer's principle of oxygen accumulation might be applied in a different way, so that a ketonic acid would be produced, the decomposition of which, in a manner analogous to that of acetoacetic acid, would lead to the formation of two molecules of lactic acid, from which the final products alcohol and carbon dioxide might be directly derived, as shown in the following formulæ:-- CHO COOH COOH CO{2} · · · ──────── CH(OH) CH(OH) CH(OH) CH{2}·OH · · · · CH(OH) CH{2} CH{3} CH{3} · · ────── ──────── CH(OH) CO COOH CO{2} · · · ──────── CH(OH) CH(OH) CH(OH) CH{2}·OH · · · · CH{2}(OH) CH{3} CH{3} CH{3} A scheme based on somewhat different principles has been propounded by Wohl [Lippmann, 1904, p. 1891], and has been accepted by Buchner and Meisenheimer [1905] as more probable than that quoted above. Wohl and Oesterlin [1901] were able to trace experimentally the various stages of the conversion of tartaric acid (I) into oxalacetic acid (III), which can be carried out by reactions taking place at the ordinary temperature, and they found that the first stage consisted in the removal of the elements of water leaving an unsaturated hydroxy derivative (II) which in the second stage underwent intramolecular change into the corresponding keto-compound (III): [p101] COOH COOH COOH · · · CH(OH) minus H = C(OH) ⇌ CO · · ║ · CH(OH) OH CH CH{2} · · · COOH COOH COOH I. II. III. Tartaric acid. Oxalacetic acid.