Prepd by boiling l-tartaric acid with alkali; as byproduct of racemization: Winther, Z. Phys. Chem. 56, 507 (1906); Holleman, Org. Synth. coll. vol. I (2nd ed., 1941) p 497; Milas, US 2414385 (1947). Microbial prepn: Martin, Foster, J. Bacteriol. 70, 405 (1955); Foster, US 2947665 (1960). Explanation of optical inactivity: Noller, Science 102, 508 (1945); C. R. Noller, Chemistry of Organic Compounds (Philadelphia, 2nd ed., 1957) p 339.