Prepn by the interaction of anhydr formic acid, potassium fluoride and benzoyl chloride (16% yield): Nyesmejanov, Kahn, Ber. 67, 203 (1946); from benzoyl fluoride and formic acid (36% yield): Masentshev, J. Gen. Chem. USSR 16, 203 (1946); from benzoyl chloride, formic acid, and KHF2 (35% yield): Olah et al., Ber. 89, 862 (1956); Olah, Kuhn, J. Am. Chem. Soc. 82, 2381 (1960); from acetic formic anhydride, CH3COOOCH, and anhydr HF (67% yield): Olah, Kuhn, ibid. 2380.