title: 3,5-Dicarboxypyridinium fluoride.
abstract: The cation of the title salt, C(7)H(6)NO(4) (+.)F(-), lies on a twofold rotation axis that passes through the N and 4-C atoms of the pyridine ring; the carb-oxy-lic acid substituent features unambiguous carbon-oxygen single and double bonds. The fluoride ion is a hydrogen-bond acceptor to two hy-droxy and one amino groups, these O-H⋯F and N-H⋯F hydrogen bonds leading to the formation of a layer structure parallel to the ab plane. The F atom lies on a position of 2 site symmetry.
authors.forename: Seik Weng
authors.initials: SW
authors.lastname: Ng
authors.forename: Yi-Ping
authors.initials: YP
authors.lastname: Tong