The single crystal and powder X-ray diffraction analyses of the title
compound, 2K(+).C4H4O62-.0.5H(2)O, are presented. The discussion conta
ins comparisons with the structures of potassium hydrogen tartrate and
calcium tartrate tetrahydrate. The title compound belongs to the clas
s of tartrates that are generally ideal for X-ray structure investigat
ions on single crystals within the framework of teaching seminars. The
relevance of the powder X-ray diffraction method in the field of wine
analysis, with a view to detecting unallowed blending of wines, is em
phasized.