Only the equilibrium mixture of the keto and enol forms is described here. Prepd from ethyl acetate by the action of sodium, sodium ethoxide, sodamide, or calcium: Inglis, Roberts, Org. Synth. coll. vol. I, 235 (2nd ed., 1941); Hansley, Schott, US 2843623 (1958 to Natl. Distillers); Scheibler, Ann. 565, 176 (1949); Gattermann-Wieland, Praxis des Organischen Chemikers (de Gruyter, Berlin, 40th ed., 1961) p 218. Discussion of keto-enol tautomerism: Ward, J. Chem. Educ. 39, 95 (1962). Absorption spectrum: Morton, Rosney, J. Chem. Soc. 1926, 711. Toxicity data: H. F. Smyth et al., J. Ind. Hyg. Toxicol. 31, 60 (1949).