Revisiting a natural wine salt: calcium (2R,3R)‐tartrate tetrahydrate.

The crystal structure of the salt calcium (2R,3R)‐tartrate tetrahydrate {systematic name: poly[[diaqua[μ4‐(2R,3R)‐2,3‐dihydroxybutanedioato]calcium(II)] dihydrate]}, {[Ca(C4H8O8)(H2O)2]·2H2O}n, is reported. The absolute configuration of the crystal was established unambiguously using anomalous dispersion effects in the diffraction patterns. High‐quality data also allowed the location and free refinement of all the H atoms, and therefore to a careful analysis of the hydrogen‐bond interactions. [ABSTRACT FROM AUTHOR]