A process for preparing 2-{1-[2-(4-chlorophenoxy)propoxyimino]-butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)cyclohex-2-enone lithium salt by reacting the corresponding acid 2-{1-[2-(4-chlorophenoxy)-propoxyimino]butyl}-3-hydroxy-5-(tetrahydrothiopyran-3-yl)-cyclohex-2-enone and lithium hydroxide and the isolation of the lithium salt are described. Here, it is advantageous to use a solvent mixture which comprises methanol and at least one aromatic hydrocarbon and to remove at least some of the solvent prior to the isolation. It is particularly preferred to dissolve the acid in an aromatic hydrocarbon, preferably toluene, and to use a methanolic lithium hydroxide solution. The product, which can be obtained in a more efficient manner by this process, furthermore has considerable advantages with respect to formulation.
