Process for the preparation of 2,6-dichloro-5-fluoronicotin-onitrile, and the chemical compound 3-cyano-2-hydroxy-5-fluoropyrid-6-one monosodium salt and tautomers thereof

2,6-dichloro-5-fluoronicotmomtrile is accessible in an advantageous manner by reaction of 3-cyano-2-hydroxy-5-fluoropyrid-6-one and/or its tautomers and/or its salts and/or tautomers thereof with phosphorus trichloride and chlorine gas in a solvent with the addition of a basic catalyst at temperatures of 30-300 DEG C and subsequent hydrolysis. The 3-cyano-2-hydroxy-5-fluoropyrid-6-one monosodium salt which can be employed is a novel chemical compound which is accessible in a simple manner from 3-cyano-2-hydroxy-5-fluoropyrid-6-one and/or tautomers thereof by reaction with an alcoholate and precipitation with a medium-strength acid.