Trisodium citrate, Na3(C6H5O7).

The crystal structure of anhydrous tris-odium citrate, Na3(C6H5O7), has been solved and refined using synchrotron X-ray powder diffraction data, and optimized using density functional theory (DFT). There are two independent five-coordinate Na(+) and one six-coordinate Na(+) cations in the asymmetric unit. The [NaO5] and [NaO6] polyhedra share edges and corners to form a three-dimensional framework. There are channels parallel to the a and b axes in which the remainder of the citrate anions reside. The only hydrogen bonds are an intra-molecular one between the hy-droxy group and one of the terminal carboxyl-ate O atoms and an intermolecular one between a methylene group and the hydroxyl O atom.